PGX Satisfast Vegan Protein Very Strawberry by Natural Factors

There is insufficient reliable information available about the effectiveness of algin.

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POSSIBLY EFFECTIVE

• Hypertension. Oral blue-green algae seem to modestly reduce blood pressure in patients with hypertension. Details: Some small clinical studies show that blue-green algae can decrease blood pressure in patients with hypertension (97206,99654). A meta-analysis of five small clinical trials in patients with hypertension, type 2 diabetes, or chronic pain shows that taking spirulina blue-green algae 1-8 grams daily for up to 12 weeks reduces systolic blood pressure (SBP) by 5 mmHg and diastolic blood pressure (DBP) by 7 mmHg when compared with placebo. The effect size was larger in patients with hypertension and in those treated for at least 12 weeks (109964). Another small clinical study shows that taking spirulina blue-green algae (A. maxima) 4.5 grams daily for 6 weeks decreases blood pressure in adults with hypertension, with the number of subjects fulfilling the criteria for hypertension decreasing from 45% to 14% when compared to baseline (18297). A more recent clinical study in patients with hypertension shows that consuming a salad dressing containing 2 grams spirulina blue-green algae daily for 8 weeks reduces SBP by around 6 mmHg and DBP by around 4 mmHg when compared to baseline. While overall reduction in blood pressure with spirulina dressing was larger when compared with patients consuming a control dressing, the study groups were heterogenous at baseline, limiting the validity of any statistical comparisons between groups (109965).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Allergic rhinitis (hay fever). It is unclear if oral blue-green algae are beneficial in allergic rhinitis. Details: Preliminary clinical research shows that taking spirulina blue-green algae (A. platensis) 2 grams daily for 6 months, improves self-rated scores for sneezing, nasal discharge, nasal congestion, and itching when compared with placebo in adults with allergic rhinitis (18300).
• Antiretroviral-induced insulin resistance. It is unclear if oral blue-green algae are beneficial for insulin resistance due to antiretrovirals. Details: Preliminary clinical research shows that taking spirulina blue-green algae (A. platensis) 19 grams daily for 2 months increases insulin sensitivity by about 225% when compared to baseline in patients with antiretroviral-induced insulin resistance (75944). The validity of this finding is limited by the lack of a comparator group.
• Anxiety. Although there has been interest in using oral blue-green algae for anxiety, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Arsenic poisoning. It is unclear if oral blue-green algae are beneficial for chronic arsenic toxicity. Details: Preliminary clinical research in people living in areas of Bangladesh with high arsenic levels in drinking water shows that taking a combination of an alcoholic extract of spirulina blue-green algae 250 mg and zinc 2 mg orally twice daily for 16 weeks, in addition to use of filtered drinking water, increases urinary arsenic excretion, reduces hair arsenic levels, and improves skin manifestations of chronic arsenic toxicity when compared with placebo plus filtered water (18301).
• Athletic performance. Most research suggests that oral blue-green algae are not beneficial for improving athletic performance; however, the available studies are small. Details: AAlthough some research disagrees, most small or preliminary clinical trials show that taking spirulina blue-green algae does not improve athletic performance in trained or untrained adults. One study shows that, when compared with placebo, taking spirulina blue-green algae (Hawaiian Spirulina, Cyanotech Corporation) 3 grams daily for up to 8 weeks has no effect on exercise output during a 30-minute elliptical trainer workout in active males (97203). In elite rugby players, taking spirulina blue-green algae (Algae Green Value) 5.7 grams daily for 7 weeks does not improve jump or sprint performance or body composition when compared to placebo (104567). In healthy untrained males, a small study shows that taking spirulina blue green algae 6 grams daily for 7 days does not increase the time to fatigue related to arm cycling following a 30-minute submaximal exercise bout (104566). In male recreational runners, spirulina blue-green algae (A. platensis) 2 grams three times daily for 4 weeks was not associated with any change in exercise intensity during a 2-hour treadmill jogging period. However, sprinting time to exhaustion following the 2-hour jog increased from 2.05 minutes to 2.7 minutes (18306). Also, a study of athletes and non-athletes shows that taking spirulina blue-green algae (Parry Nutraceuticals) 2 grams daily for 8 weeks has a small effect on isometric muscle strength, but not muscle endurance, when compared with placebo (104568).
• Attention deficit-hyperactivity disorder (ADHD). Oral blue-green algae have only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking 3 mL of a specific combination of spirulina blue-green algae, peony, ashwagandha, gotu kola, bacopa, and lemon balm (Nurture and Clarity, Tree of Healing-LD) diluted in 50-60 mL of water three times daily for 4 months improves ADHD scores when compared with placebo in previously untreated children aged 6-12 years (19272). It is unclear if this effect is due to blue-green algae, other ingredients, or the combination.
• Beta-thalassemia. It is unclear if oral blue-green algae are beneficial in beta-thalassemia. Details: In children with beta-thalassemia, preliminary clinical research shows that taking spirulina blue-green algae (GNC Natural Brand Spirulina, General Nutrition Corporation) 250 mg/kg daily, up to a maximum dose of 4 grams daily, for 3 months reduces the percentage of children requiring blood transfusion during an interval of less than 2 weeks from 66% to 40%. There were also improvements in red blood cell count and levels of hemoglobin, ferritin, and liver function enzymes (104569). However, the validity of these findings is limited by the lack of a comparator group.
• Blepharospasm. It is unclear if oral blue-green algae are beneficial when used in conjunction with botulinum toxin injections. Details: Preliminary clinical research shows that taking a specific product containing the blue-green algae species Aphanizomenon flos-aquae (Super Blue-Green Algae, Cell Tech) 1500 mg per day orally for 6 months in addition to botulinum toxin-A injections does not reduce eyelid spasms when compared with botulinum toxin-A alone in people with essential blepharospasm or Meige syndrome (14842).
• Cancer. Although there has been interest in using oral blue-green algae for cancer, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Cardiovascular disease (CVD). Although there has been interest in using oral blue-green algae for CVD, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Cognitive Impairment. It is unclear if oral blue-green algae are effective for improving cognitive impairment. Details: A small clinical study in patients aged 60 or older with mild cognitive impairment shows that taking blue-green algae extract 1 gram 3 times daily for 12 weeks slightly improves some components of cognitive function testing related to visual learning, memory, and vocabulary when compared with placebo (112001). However, the validity of these findings is limited by lack of adjustment for multiple comparisons, which may explain the discrepant results with the other components of the cognitive function tests.
• Depression. Although there has been interest in using oral blue-green algae for depression, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Diabetes. It is unclear if oral blue-green algae are beneficial in diabetes. Details: A meta-analysis of seven small clinical studies in patients with type 2 diabetes shows that taking spirulina blue-green algae 0.8-14 grams daily for 6-12 weeks reduces fasting blood glucose and improves total cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol, but does not affect low-density lipoprotein (LDL) cholesterol, when compared with placebo. There was no reduction in glycated hemoglobin (HbA1c); however, all but two of the studies lasted less than 12 weeks, limiting the validity of the findings related to HbA1c (109970).
• Dyslipidemia. It is unclear if oral blue-green algae are beneficial in dyslipidemia. Details: Several clinical studies in patients with normal or elevated cholesterol levels show that doses of spirulina blue-green algae (A. platensis, A. maxima, A. fusiformis) ranging from 1-10 grams daily for 1-6 months may reduce total cholesterol by 8% to 27%, low-density lipoprotein (LDL) cholesterol by 10% to 65%, and triglycerides by 0% to 23%; and increase high-density lipoprotein (HDL) cholesterol by 0% to 66% (18297,18298,18299,91705,91708,91710,91717,102689). However, the validity of these studies is limited by methodological weaknesses and heterogeneous population characteristics. A meta-analysis of 23 small studies, several of which were in patients with type 2 diabetes or obesity, shows that taking blue-green algae 0.8-10 grams for 4 to 24 weeks modestly improves levels of LDL, HDL, triglycerides, and total cholesterol when compared with placebo or no treatment (112004). The interpretation of these findings is limited by the high heterogeneity of the included studies which enrolled patients of varying health status and employed various study designs.
• Dyspepsia. Although there has been interest in using oral blue-green algae for dyspepsia, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Exercise-induced muscle soreness. It is unclear if oral blue-green algae are effective for the prevention of exercise-induced muscle soreness. Details: A small clinical study in recreationally trained males shows that taking spirulina blue-green algae 2 grams three times daily does not reduce delayed onset muscle soreness after eccentric exercise when compared with placebo (109967).
• Hepatitis C. Evidence for the use of oral blue-green algae in hepatitis C is conflicting. Details: One clinical study in adults with chronic hepatitis C who are unresponsive to interferon treatment shows that taking spirulina blue-green algae (A. platensis) 500 mg orally three times daily for 6 months is associated with greater improvements in alanine aminotransferase (ALT) levels than taking silymarin 140 mg three times daily. Complete virological response rates were 13% with blue-green algae and 3% with silymarin, although this difference was not statistically significant (63247). However, in another study in people with chronic hepatitis B or C, liver function enzyme levels worsened after one month of treatment with oral spirulina blue-green algae (18304).
• HIV/AIDS. It is unclear if oral blue-green algae are beneficial for people with HIV/AIDS who do not have access to antiretrovirals. Details: One clinical study in adults with untreated HIV shows that taking spirulina blue-green algae (A. platensis) powder 5-10 grams daily for 3-6 months does not affect CD4 counts, viral load, or weight gain in patients with HIV (75927,91707). However, in one study, the incidence of opportunistic infections, respiratory disease, gastrointestinal symptoms, and fatigue was 43% for patients taking spirulina blue-green algae, compared to 70% for patients taking placebo (91707).
• Iron deficiency anemia. Although there has been interest in using oral blue-green algae for iron deficiency anemia, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Lichen planus. It is unclear if oral blue-green algae are beneficial in patients with oral lichen planus. Details: A small clinical study in patients with oral lichen planus shows that taking spirulina blue-green algae 500 mg twice daily for 8 weeks along with application of triamcinolone acetonide 0.1% oral paste three times daily for 1 week reduces pain and lesion size when compared with only triamcinolone acetonide three times daily for 8 weeks (109963).
• Malnutrition. Evidence for the use of oral blue-green algae in malnutrition is conflicting. Details: Some clinical research in severely undernourished children shows that adding spirulina blue-green algae (A. platensis) 5 grams orally twice daily for 8 weeks to a traditional diet results in an average daily weight gain of 25 grams, compared with only 15 grams for those given the traditional diet alone. Similarly, giving blue-green algae 10 grams twice daily for 8 weeks in addition to a misola diet (millet, soy, peanut kernel, sugar, and salt) results in an average daily weight gain of 34 grams, compared with only 20 grams for children given the misola diet alone (18308). However, a small clinical study in malnourished children aged 3 months to 3 years shows that giving spirulina blue-green algae 5 grams daily for 3 months in addition to a traditional diet fails to increase weight gain more than the traditional diet alone (18309). Similarly, a moderate-size crossover study in preschool-aged children in Cambodia shows that taking blue-green algae 2 grams 5 times a week during the first hour of school for 8 weeks does not improve weight gain or height but may reduce the proportion of children with anemia when compared with placebo (112002). The interpretation of these findings is limited by the high rate of patients lost to follow-up and the lack of statistical adjustment for confounding factors, such as parasitism and home diet.
• Memory. Although there has been interest in using oral blue-green algae for memory, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Menopausal symptoms. It is unclear if oral blue-green algae are beneficial for improving symptoms of menopause. Details: A preliminary clinical study shows that taking a product containing the blue-green algae species Aphanizomenon flos-aquae (Klamin, Nutrigea) 1.6 grams daily for 8 weeks reduces anxiety and depression when compared with placebo in menopausal adults aged 50-60 years. The treatment has no effect on vasomotor symptoms or hormone levels (18310).
• Mental alertness. It is unclear if oral blue-green algae are beneficial for reducing mental fatigue. Details: A preliminary clinical study shows that taking spirulina blue-green algae (Hawaiian Spirulina, Cyanotech Corporation) 3 grams daily for up to 8 weeks improves performance on a mathematical based mental fatigue test in healthy men when compared with placebo. Subjective improvement in mental alertness over placebo was also reported (97203).
• Metabolic syndrome. It is unclear if oral blue-green algae are beneficial in patients with metabolic syndrome. Details: A small clinical study in patients with metabolic syndrome shows that taking spirulina blue-green algae (Spirulysat, AlgoSource), providing phycocyanin 20 mg, daily for 12 weeks improves triglyceride levels, but does not reduce body mass index, waist circumference, blood pressure, glycemic indices, or other lipid levels, when compared with placebo (109971).
• Nonalcoholic fatty liver disease (NAFLD). Although there has been interest in using oral blue-green algae for NAFLD, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Obesity. Evidence for the use of blue-green algae in obesity is conflicting. Details: Small, low-quality clinical trials have shown mixed results in people with obesity (18295,91717,97205,99655,99703,102688). When results are analyzed together, there is evidence of a very small benefit for both body weight and plasma lipid levels. Two meta-analyses show that taking spirulina blue-green algae may increase weight loss by up to 1.85 kg when compared with placebo (102690,104565). A greater effect is seen in patients with obesity when compared with overweight patients. In addition, there is a small effect on fat loss (102690). However, there is evidence from two studies lasting longer than 12 weeks that taking blue-green algae may slightly increase BMI (104565). A meta-analysis of small clinical trials also shows that taking spirulina blue-green algae reduces fasting blood sugar and total cholesterol levels by a small amount when compared with placebo, but has no effect on low-density lipoprotein (LDL) cholesterol or triglyceride levels, in patients with obesity (102689). When combined with an exercise program, taking spirulina blue-green algae increases weight loss by 1.4 kg and improves exercise tolerance and total, LDL, and high-density lipoprotein (HDL) cholesterol levels when compared with exercise alone (99655,102688). Doses have included a specific product containing the spirulina blue-green algae species A. fusiformis (Multinal, New Ambadi Estate Pvt. Ltd.) 1 gram twice daily or four times daily for 3 months (91717) or spirulina blue-green algae 2 grams daily for 3 months, or 4.5 grams daily for 6 weeks, alone or in combination with exercise (97205,99655,102688).
• Oral leukoplakia. It is unclear if oral blue-green algae are beneficial for oral leukoplakia in tobacco chewers. Details: Preliminary clinical research shows that taking spirulina blue-green algae (A. fusiformis) orally 1 gram daily for 12 months produces regression of precancerous oral leukoplakia lesions in 45% of tobacco chewers, compared to only 7% of those receiving placebo. Regression rates appear to be highest in those with homogeneous lesions and lowest in those with ulcerated or nodular lesions (15782).
• Periodontitis. It is unclear if injecting blue-green algae into periodontal pockets is beneficial in periodontitis. Details: Preliminary clinical research shows that injecting a 4% w/v gel prepared from spirulina blue-green algae into periodontal pockets of adults with chronic periodontitis, after scaling and root planing, is associated with a decrease in probing pocket depth of 1.57 mm after 120 days, compared with only 0.84 mm in patients receiving scaling and root planing alone (91709).
• Premenstrual syndrome (PMS). Although there has been interest in using oral blue-green algae for PMS, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Stress. Although there has been interest in using oral blue-green algae for stress, there is insufficient reliable information about the clinical effects of blue-green algae for this condition.
• Ulcerative colitis. It is unclear if oral blue-green algae are beneficial in patients with ulcerative colitis. Details: A small clinical study in patients with ulcerative colitis shows that taking spirulina blue-green algae 500 mg twice daily for 8 weeks improves quality of life scores and reduces stress and sleep disturbances when compared with placebo. However, there was no effect on most measures of sleep quality, mood, and fatigue (109969).
• Wound healing. Although there has been interest in using oral blue-green algae for wound healing, there is insufficient reliable information about the clinical effects of blue-green algae for this condition. More evidence is needed to rate blue-green algae for these uses.

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INSUFFICIENT RELIABLE EVIDENCE to RATE

• Dementia. It is unclear if consuming dewaxed brown rice improves cognitive function in adults with dementia. Details: A small clinical study in elderly nursing home residents with low cognitive function shows that eating dewaxed brown rice with 3 meals daily for 6 months improves scores on the Revised Hasegawa's Dementia Scale to a greater extent than eating white rice (103626).
• Diabetes. It is unclear if consuming brown rice as part of the diet is beneficial for improving glycemic control in adults with type 2 diabetes; the available research is conflicting. Details: Meta-analyses of clinical trials evaluating adults with type 2 diabetes shows that consuming a diet containing brown rice 50-450 grams daily for 4-104 weeks does not improve glycated hemoglobin (HbA1c) levels or fasting blood glucose levels when compared with a white rice diet (108661,108662). Clinical trials using non-glutinous brown rice for 24 hours or 16 weeks show similar results (96996,96998). However, not all research agrees. Preliminary clinical research in adults with type 2 diabetes shows that eating glutinous brown rice twice daily for 8 weeks modestly reduces HbA1c levels, compared with no change in those eating white rice (96995). Preliminary clinical research also shows that eating glutinous brown rice as the staple food over a 24-hour period helps with acute glycemic response when compared with white rice (96996). Other preliminary clinical research in females with type 2 diabetes shows that following a brown rice diet for 12 weeks reduces HbA1c and fasting blood glucose by 3% to 5% and reduces body weight and body fat by approximately 2% when compared with no intervention (18660). Clinical trials in adults with type 2 diabetes also report conflicting effects of brown rice on body weight, waist circumference, body fat, lipids, and blood pressure when compared with white rice (108661,108662). However, the limited studies showing positive benefits of brown rice report very minor effects with unclear clinical implications. The reasons for these discrepancies are unclear but may be related to the slight differences between the varieties of brown rice.
• Impaired glucose tolerance (Prediabetes). It is unclear if consuming brown rice as part of the diet is beneficial for improving glycemic control; the available research is conflicting. Details: A meta-analysis of clinical trials evaluating adults with prediabetes shows that consuming a brown rice-based diet for 6-12 weeks does not improve glycated hemoglobin (HbA1c) levels, fasting blood glucose levels, body weight, or waist circumference when compared with a white rice-based diet (108662). However, some preliminary clinical research in middle-aged females with prediabetes shows that replacing staple white rice in the diet with pre-germinated brown rice for 4 months modestly reduces fasting blood glucose and HbA1c levels when compared with baseline. There were also small improvements in body fat, body mass, systolic and diastolic blood pressure, and total cholesterol levels when compared with baseline (96997). The validity of these findings is limited by the lack of a comparator group.
• Metabolic syndrome. It is unclear if consuming brown rice reduces the prevalence of metabolic syndrome or improves metabolic parameters in patients with this condition. Details: Preliminary clinical research in adults with metabolic syndrome shows that eating brown rice ad libitum for 16 weeks does not improve metabolic factors or reduce the number of patients still meeting the diagnosis of metabolic syndrome when compared with eating white rice ad libitum (96998). However, other clinical research shows that eating 200 grams daily of cooked, pre-germinated brown rice for 3 months reduces the number of patients meeting the diagnosis of metabolic syndrome by 30%, compared with a reduction of 10% in those eating 200 grams daily of cooked white rice (103627). This suggests that any benefit might be related to regular consumption of brown rice. A small clinical study in overweight adults with metabolic syndrome shows that eating brown rice with 2 meals per day, 6 days per week for 3 months, reduces glycated hemoglobin (HbA1c) when compared with eating the same amount of white rice (103623). Other preliminary clinical research shows that eating sticky or glutinous brown rice for 8 weeks modestly improves body weight, some measures of insulin resistance, and levels of low-density lipoprotein (LDL) cholesterol when compared with baseline (96999). The validity of these findings is limited by the lack of a comparator group.
• Obesity. Although there is interest in using oral brown rice for weight loss, there is insufficient reliable information about the clinical effects of brown rice for this purpose.
• Psoriasis. Although there is interest in using oral brown rice for psoriasis, there is insufficient reliable information about the clinical effects of brown rice for this condition. More evidence is needed to rate brown rice for these uses.

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EFFECTIVE

• Dyspepsia. Oral calcium carbonate is approved by the US Food and Drug Administration (FDA) as an antacid. Details: Taking calcium carbonate orally as an antacid is effective for treating dyspepsia (1843). Calcium carbonate has FDA approval as an antacid.
• Hyperkalemia. Intravenous calcium gluconate is approved by the US Food and Drug Administration (FDA) for preventing hyperkalemia-induced cardiac abnormalities. Details: Administering calcium gluconate intravenously can reverse electrocardiographic changes and arrhythmias induced by hyperkalemia (12946). Intravenous calcium gluconate is FDA-approved for preventing hyperkalemia-induced cardiac abnormalities.
• Hypocalcemia. Oral calcium treats and prevents hypocalcemia. Intravenous calcium is used to treat severe hypocalcemia. Details: Taking calcium orally is effective for treating and preventing hypocalcemia. Intravenous calcium gluconate, acetate, gluceptate, or chloride is effective for severe hypocalcemia or hypocalcemic tetany (12928).
• Kidney failure. Oral calcium carbonate or calcium acetate is used as a phosphate binder during kidney failure. Details: Taking calcium carbonate or calcium acetate orally is effective as a phosphate binder. Calcium acetate (PhosLo) appears to control hyperphosphatemia better than sevelamer (Renagel) (12943,12944,38990). Calcium citrate is not recommended for this purpose because it increases aluminum absorption and does not bind phosphate as efficiently as calcium acetate or calcium carbonate (21631). Some clinical research also shows that taking calcium orally reduces blood pressure in patients with kidney failure (975).

LIKELY EFFECTIVE

• Corticosteroid-induced osteoporosis. Oral calcium in combination with vitamin D prevents bone density loss that occurs during long-term treatment with corticosteroids. Details: Taking calcium in combination with vitamin D as adjunctive therapy seems to be effective for reducing bone mineral density loss in people using corticosteroids long-term (982,1046,1830,1831,1832,4462,4463,4464,4465,4466)(4467,12945,38493). One specific product used in clinical research is Oscal (Marion Merrel Dow Inc.), which contains elemental calcium 500 mg per tablet plus vitamin D 125 IU per tablet (982). Another product used is Oscal 250 + D (SmithKline Beecham Healthcare), which contains elemental calcium 250 mg and vitamin D 125 IU per tablet (1046).
• Hyperparathyroidism. Oral calcium reduces parathyroid hormone levels in patients with secondary hyperparathyroidism due to kidney failure. Details: Taking calcium orally reduces parathyroid hormone levels in patients with kidney failure and secondary hyperparathyroidism (1827,1828,1829,39174,39425). In elderly women, the combination of calcium and vitamin D reverses secondary hyperparathyroidism and reduces hip fracture risk (8818). Also, population research suggests increased calcium intake from the diet and supplements reduces the risk of primary hyperparathyroidism in women. Supplemental intakes of at least 500 mg/day and dietary intakes of approximately 1100 mg/day are considered to be protective (91353).
• Osteoporosis. Adequate calcium intake, from the diet and/or supplements, is recommended for the prevention and treatment of osteoporosis. Details: The Bone Health and Osteoporosis Foundation (BHOF) recommends ensuring adequate calcium intake in line with the recommended dietary allowance (RDA) by age, along with adequate vitamin D intake, for the prevention and treatment of osteoporosis in adults over 50 years of age. Supplementation can be used to augment dietary intake when adequate dietary intake is not feasible (109425). In the US and Canada, foods containing at least 200 mg calcium with less phosphorous content than calcium can be labelled with a health claim regarding the relationship between adequate calcium intake and a reduced risk for osteoporosis (11940,102148). However, calcium supplementation is not recommended specifically for the primary prevention of osteoporosis. The US Preventive Task Force (USPSTF) states that the current evidence is insufficient to assess the balance of benefits and harms of vitamin D and calcium supplementation, alone or in combination, for the primary prevention of fractures in community dwelling adults without osteoporosis (95695). Also, calcium supplements do not seem to be effective for preventing loss of bone mineral density (BMD) during lactation (988), in patients who have had bone marrow transplantation (1817), or in patients who have had renal transplantation (4823,38736,38871). Maximal bone growth occurs in the teenage years, and then BMD in females remains relatively constant until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In males, this occurs several decades later. Bone loss is more pronounced if dietary calcium intake is below the RDA, which is the case for many Americans (2571,2578). One meta-analysis of randomized controlled trials in healthy children 7-14 years old shows that fortifying food with calcium 250-1000 mg daily for up to 24 months modestly improves femoral neck BMD, but not hip or spine BMD. However, the included trials did not supplement vitamin D (107232). During the 5 years immediately after menopause, calcium supplementation has very little effect on bone loss (2569,2570,2575,2576). The rapid loss of estrogen causes a high bone resorption rate, which increases serum calcium levels and therefore decreases intestinal absorption of calcium (2570). After this period, the typical rate of bone loss is 2% per year (2572,2576). Taking calcium 1000-1600 mg daily as carbonate, citrate, lactate gluconate, or citrate malate salt decreases this rate by 0.25% to 1% annually (977,979,981,2569,2571,2572,2575,2576,2578,6850)(38978,38980,39064). The greatest reductions (1% or more) are seen in the first 1-2 years of supplementation when bone remodeling foci can be filled (2569,2576). After this period, the differences in rate of loss between supplemented and non-supplemented females are closer to 0.25% per year (2569,2577). A meta-analysis of clinical evidence suggests that there is no additional benefit after 4 years (38980). Small clinical studies have found that continuous calcium supplementation at an average daily dose of 1050 mg, started after menopause and continued for 1.5-4 years, may reduce fracture rates by 26% when compared with no calcium supplementation. The largest of these studies was conducted in nursing home residents who also received daily vitamin D; the benefits of calcium, specifically, are unclear (39386). Some research also suggests that calcium and vitamin D improves primary prevention of osteoporotic fractures in some older individuals with osteoporosis, particularly the elderly and those who are no longer community dwelling (12930,38875,38849,39026,109471). However, not all research is positive. One large clinical trial in elderly adults with a low-trauma fracture show that taking calcium 1000 mg daily with or without vitamin D 800 IU daily for 2-7 years does not reduce the risk of a second fracture when compared with placebo (13073). Another clinical study shows that taking calcium 1000 mg daily plus vitamin D 800 IU daily does not prevent a second fracture in elderly patients, or prevent a first fracture in elderly patients with other risk factors such as low body weight (less than 58 kg, 127.6 pounds), smoking, family history of hip fracture, or fair or poor self-reported health (12929). Also, some exploratory research suggests that supplements may need to be continued indefinitely; in adults over 68 years of age, any effects of 2 years of calcium supplements on BMD appear to be lost within 2 years after discontinuing supplements (6853). Calcium has additive effects when used with other agents such as vitamin D, estrogens, or calcitonin. Whereas calcium alone generally reduces or prevents loss of BMD, combination with other agents can produce small increases in BMD ranging from 0.3% to 3.3% depending on the combination and dosages used (978,980,1836,2570,2571,2572,2576). However, one meta-analysis in healthy adults shows that fortifying foods with calcium 250-1000 mg daily, in conjunction with vitamin D supplementation, for up to 24 months does not improve BMD when compared with control (107232). The full potential of osteoporosis treatments cannot be realized without adequate calcium intake (2569,2570,2571,2572). Advise patients taking agents such as estrogens, calcitonin, bisphosphonates, or raloxifene (Evista) to ensure that their daily calcium intake meets the RDA. Use supplements if necessary. The usefulness of calcium in preventing osteoporosis in males is not as well-studied. Some observational research has found that calcium 870 mg daily is not associated with changes in BMD and bone loss in males (97201). However, clinical evidence suggests that taking calcium 1000 mg daily for 2 years might improve trabecular or cortical bone mass by 2% to 4% (980,8827,8873). Dietary supplementation with calcium and vitamin D seems to moderately reduce bone loss measured in the femoral neck, spine, and total body, and seems to reduce the incidence of nonvertebral fractures in older patients with osteopenia or low BMD (980).
• Premenstrual syndrome (PMS). Adequate calcium intake seems to prevent symptoms of PMS. Details: There seems to be a link between low dietary calcium intake and symptoms of PMS (2004,6847,39007). Taking calcium 1000-1336 mg daily seems to significantly reduce depressed mood, water retention, and pain, especially if daily calcium intake is inadequate (1822,1823,1824,2004,95821). Calcium carbonate 1200 mg daily seems to decrease PMS symptom scores by about 18% when compared with placebo (1822). Increasing dietary calcium intake is also associated with a decreased risk of developing PMS. Consuming an average of 1283 mg of calcium per day from foods is associated with about a 30% lower risk of developing PMS compared with consuming an average of 529 mg daily (13094); however, taking calcium supplements does not appear to be associated with the risk of developing PMS.

POSSIBLY EFFECTIVE

• Colorectal cancer. Oral calcium seems to be beneficial for preventing colorectal cancer, especially in those with adequate vitamin D levels and normal body mass index (BMI). Details: Population studies have found that increased intake of dietary or supplemental calcium is associated with a reduced risk of colorectal cancer and colorectal adenomas (1047,8820,12120,38951,98898,98899). Clinical trials and meta-analyses of clinical research also show that taking calcium supplements 1.2-2 grams daily for up to 4 years can reduce the risk of colorectal adenoma recurrence by up to 29% (970,12118,12950,15267,34596,38718,39042,95817). However, not all research has been positive. Some meta-analyses of clinical research or observational studies suggest that taking calcium does not reduce the risk of familial adenomatous polyposis or colorectal cancer (34596,39042,39349). Other contradictory research suggests that postmenopausal females who take calcium 1000 mg daily plus vitamin D 400 IU daily do not have a reduced risk of developing colorectal cancer (14290); however, this finding may not be reliable due to the high baseline intake of calcium in study participants. The reason for these conflicting findings is not entirely clear. Vitamin D might be an important factor. People with lower than average vitamin D levels do not seem to get any benefit from calcium supplements (12118). Also, one meta-analysis of previous trials suggests that taking calcium 1200 mg daily reduces the risk of colorectal adenomas in people with a normal BMI, but not in those who are overweight or obese (99715). Despite this conflicting evidence, the US Food and Drug Administration (FDA) approved a qualified health claim in 2005 stating that calcium supplements may reduce the risk of colorectal cancer and colorectal adenomas. However, the FDA has determined that there is little scientific evidence to support this claim (102366).
• Fetal bone mineralization. If calcium intakes are low during pregnancy, oral calcium seems to be beneficial for increasing fetal bone density. Details: With low dietary calcium intake (less than 562 mg elemental calcium daily) during pregnancy, calcium supplementation increases fetal bone mineralization and density. However, calcium supplementation does not offer any additional benefit if calcium intakes are adequate (3263,3264).
• Hypertension. Oral calcium seems to reduce blood pressure by a small amount. However, it is unclear if this reduction is clinically significant. Details: Many clinical trials and observational studies show that intake of calcium supplements or dietary calcium modestly reduces blood pressure in patients with or without hypertension, usually around 1-2 mmHg. Calcium seems to be more effective for certain subpopulations of patients, such as salt-sensitive people and patients with low baseline dietary calcium intake (945,972,974,976,984,1818,1819,1820,1821,6852)(13138,14406,38803,39063,39094,39221). Also, a meta-analysis of clinical research shows that calcium intake during pregnancy reduces systolic blood pressure in offspring by 1-2 mmHg (38852). However, a large-scale clinical trial in postmenopausal females shows that taking vitamin D (cholecalciferol) 400 IU daily in combination with elemental calcium 1000 mg daily does not lower blood pressure or reduce the risk of developing hypertension (16714). Additionally, a meta-analysis of 8 clinical trials shows that taking calcium in combination with vitamin D for up to 7 years has no effect on blood pressure (98861). The validity of this finding is limited by the poor methodological quality of the included studies. Some observational research suggests that calcium can reduce the risk for hypertension. Population research in females aged 45 years and older suggests that higher intake of calcium from both diet and supplement sources is linked to a lower risk of developing hypertension when compared to lower calcium intake (14265). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim stating that calcium supplements may reduce the risk of hypertension. However, the FDA has concluded that this claim is based on supporting, rather than conclusive, evidence (102367).
• Osteomalacia. Oral calcium seems to reverse osteomalacia caused by very low calcium intakes. Details: Osteomalacia is commonly caused by vitamin D deficiency; however, very low calcium intake can also lead to osteomalacia in children and adults. Calcium supplementation can reverse osteomalacia caused by calcium deficiency. Along with appropriate vitamin D supplementation, individuals at risk of osteomalacia need sufficient calcium intake (94819).
• Pre-eclampsia. Oral calcium seems to reduce the risk of pre-eclampsia in high risk pregnancies, especially if calcium intakes are low. Details: Although there is some conflicting evidence (971,38756), most clinical research shows that taking calcium orally 1-2 grams daily reduces pregnancy-related hypertension and pre-eclampsia (973,1833,8828,39043,39319,39426,96480). Calcium appears to reduce the risk of pre-eclampsia by about 50% when compared with placebo. One meta-analysis of 19 controlled trials involving over 29,000 pregnancies found that for every 19 females treated with calcium, one episode of pre-eclampsia would be avoided (96480). Calcium appears to have the greatest effect in individuals at high-risk of pre-eclampsia or with low calcium levels, and when taken at greater than or equal to 20 weeks of gestation (15029,38497,96480,99714). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim regarding the use of calcium supplements to reduce the risk of pregnancy-induced hypertension and pre-eclampsia. However, due to the limited and conflicting research available at that time, the FDA stated that this outcome was highly unlikely. Since then, large, high-quality clinical research has supported this finding. In fact, in 2016 the World Health Organization (WHO) released a recommendation to prescribe oral calcium supplementation 1.5-2 grams daily during pregnancies at high risk of pre-eclampsia if dietary calcium intakes are low, in order to prevent pre-eclampsia (97347).
• Rickets. Oral calcium seems to reverse rickets caused by very low calcium intakes. Details: Rickets is commonly caused be vitamin D deficiency; however, very low calcium intake can also lead to rickets. Calcium supplementation can reverse rickets caused by calcium deficiency (94819). A small clinical study in children with nutritional rickets shows that taking calcium 500-2000 mg daily for 24 weeks improves radiographically measured rickets caused by calcium deficiency. Rickets seems to improve more rapidly with calcium 1000 mg compared to calcium 500 mg. However, increasing the calcium dose to 2000 mg daily is not more beneficial than calcium 1000 mg daily (98904).
• Tooth retention. Oral calcium with vitamin D seems to help with tooth retention in the elderly population. Details: A clinical trial in the elderly population shows that taking calcium citrate malate 500 mg daily along with vitamin D3 (cholecalciferol) 700 IU daily orally for 3 years reduces the risk of tooth loss by about 52% when compared with placebo (8816).

POSSIBLY INEFFECTIVE

• Breast cancer. Oral calcium does not seem to be beneficial for breast cancer prevention. Details: Although some population research disagrees (15631,39041,95811,107237), most research shows that increased calcium intake is not associated with a reduced risk of breast cancer (15631,16715,98895,107236,107237). Subgroup analyses of population research suggest that calcium intake may reduce the risk of breast cancer in postmenopausal, but not pre-menopausal, adults (15631,107237). Another subgroup analysis in a large meta-analysis of population research also suggests that dietary intake may reduce estrogen receptor(ER)-negative breast cancer, but not ER-positive breast cancer (107236). However, most other research has not evaluated the effects of calcium supplementation or intake on breast cancer subtypes. The best evidence to date, from a large scale clinical trial (Women's Health Initiative), shows that taking vitamin D (cholecalciferol) 400 IU daily plus calcium 1000 mg daily for 7 years after menopause does not reduce the risk of developing invasive breast cancer at the end of the study and 5 years after the end of the intervention (16715,98895).
• Fractures. Although oral calcium prevents fractures in osteoporosis, most evidence shows that calcium does NOT prevent factures in people who do not have osteoporosis. See Osteoporosis discussion for more information on the use of calcium for this purpose. Details: The most recent and robust meta-analysis of clinical research shows that calcium supplementation with or without vitamin D is NOT associated with reduced fractures in older adults without osteoporosis (95822). A large-scale study in postmenopausal females aged 50-79 years suggests calcium 1000 mg plus vitamin D 400 IU daily for 7 years only modestly improves bone mineral density (BMD) and does not significantly reduce fracture risk. This lack of effect may have been due to low adherence to the treatment regimen. In those who were 80% adherent, the combination of calcium plus vitamin D reduced the risk of hip fracture by about 29% (14282). Also, some clinical research shows that taking calcium carbonate 1000 mg and vitamin D 400 IU for 5 years does not attenuate loss of height after menopause when compared with placebo (95810). Additional meta-analyses of clinical and observational evidence suggest that calcium supplementation is not associated with a reduced risk of vertebral or nonvertebral fractures, such as hip fractures (38589,38888,98895). Some other research has suggested that calcium in combination with vitamin D reduces fracture risk in older patients without osteoporosis (980,1836,8818,12930,12933,12952,38849,102145,107235); however, this research is confounded by a number of variables, including the presence of hormonal therapy and differing levels of fracture risk at baseline (1836,8818,95822). Conflicting findings on this topic might also be due to genetic differences in patient populations. A population analysis of the Women's Health Initiative study found that, in older females with the lowest genetic susceptibility to low bone mineral density (BMD), taking calcium with vitamin D is associated with a reduction in fracture risk. However, in females with a higher genetic susceptibility to low BMD, there is no association between supplementation and fracture risk. This might be because individuals with a lower susceptibility to low BMD are also more responsive to calcium and vitamin D supplementation (97357). As of April 2018, the U.S. Preventative Services Task Force (USPSTF) concludes that there is insufficient evidence to determine whether supplementing with vitamin D >400 IU daily along with calcium >1000 mg daily is safe and effective for preventing fractures in community dwelling adults without vitamin D deficiency, osteoporosis, or a history of fracture. USPSTF recommends against supplementing with calcium 1000 mg daily or less along with vitamin D 400 IU daily or less for preventing primary fractures in community-dwelling postmenopausal females (95695).
• Obesity. Oral calcium does not seem to improve weight loss. Details: Observational research has found that adults and children with low calcium intake are more likely to gain weight, have a higher body mass index (BMI), and be overweight or obese when compared to people with high calcium intake (12124,12125,12126,12127,14265). Additional observational research has found that increasing calcium intake is associated with weight loss in females; the results in males have been conflicting (12127,15602,15603). Despite these findings from observational research and a few small clinical studies (12128,15397,14438,98905), most clinical research has found that increased calcium intake does not increase weight loss (12052,13138,15396,15399,38985,39004,97356). The most recent meta-analysis of 20 clinical studies shows that daily dietary and supplemental calcium intake that meets the dietary reference intake (DRI) of 1000 mg or more daily does not increase weight loss in overweight individuals or patients with obesity when compared with intake below the DRI (95813). An older meta-analysis of 13 clinical trials also shows that increased dietary and supplemental calcium intake does not increase weight loss (15605).
• Overall mortality. Oral calcium does not seem to reduce overall mortality. Details: While some population research has found that calcium taken in combination with vitamin D in older females is associated with a lower risk of death (97353), most evidence shows that calcium, with or without vitamin D, has no effect on all-cause mortality (93533,97308).

INEFFECTIVE

• Cardiovascular disease (CVD). Oral calcium does not reduce the risk of developing CVD and may actually increase risk in some patients. Details: Clinical research shows that calcium does not decrease CVD risk. Several separate meta-analyses of clinical and population research involving over 50,000 patients show that taking calcium 600-1200 mg daily for up to 7 years does not reduce the risk of CVD-related outcomes, including stroke and myocardial infarction, cardiovascular death, or overall mortality (39018,91350,92994,93533,97308,98902,107231,107233). No association was found between total dietary or supplemental calcium intake with or without vitamin D and the risk of CVD or mortality (91350,93533,97308). In fact, some population and clinical research has found that when calcium is used alone or with vitamin D, there is an INCREASED risk of CVD and coronary heart disease (38077,107233). However, other clinical research disagrees (93533). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of CVD and coronary heart disease by 1.1-1.2 times when compared with control. However, the majority of the included research evaluated postmenopausal females and it is unclear if this finding is applicable to other populations (107233).
• Chemotherapy-induced peripheral neuropathy. Intravenous calcium does not prevent nerve pain in patients given oxaliplatin. Oral calcium has not been evaluated for this purpose. Details: While pooled analyses of cohort studies and randomized controlled trials suggest that calcium and magnesium infusion decreases the incidence of oxaliplatin-induced neurotoxicity, a meta-analysis of only randomized controlled trials shows that the infusion has no effect in preventing neurotoxicity (90028,90029,90031). Additionally, clinical trials show that administering calcium gluconate 1 gram with magnesium sulfate 1 gram intravenously immediately before, or before and after, the administration of a single oxaliplatin cycle (90005), or over the entire 6-cycle course of oxaliplatin, does not improve symptoms of neurotoxicity when compared with placebo (96474).
• Myocardial infarction (MI). Oral calcium does not prevent MI. When taken in the absence of vitamin D, oral calcium may increase the risk of MI. Details: Population research has found that increased dietary intake of calcium is associated with a decreased risk of MI (91350). However, a 2010 meta-analysis of clinical research shows that taking calcium at a dose of at least 500 mg daily is associated with an approximate 30% INCREASE in the risk of MI in patients over the age of 40. According to this analysis, one additional case of MI will occur for every 69 patients that take calcium for 5 years (17482). A more recent meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of MI by 1.2 times when compared with control. However, the majority of the included research studied postmenopausal females and it is unclear if this finding is applicable to other populations (107233) In contrast, other meta-analyses of clinical research have shown that taking calcium for up to 7 years is NOT associated with an increased risk of MI, including a meta-analysis that only included postmenopausal females (93533,107231). Reasons for these discrepancies are not entirely clear. It may relate to whether calcium is taken as monotherapy or in combination with vitamin D. When taken with vitamin D, which is commonly recommended, calcium supplementation does not appear to be associated with an increased risk of MI in postmenopausal females (93533). Also, the association between calcium supplementation and MI risk may be influenced by the amount of calcium consumed as part of the diet. Supplementation with calcium may be associated with an increased risk of MI in people with dietary calcium intake above 805 mg daily, but not in those with dietary calcium intake below 805 mg daily (17482)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alcohol use disorder. It is unclear if oral calcium is beneficial for alcohol use disorder. Details: Preliminary clinical research shows that taking calcium carbonate 800 mg and vitamin D 200 IU orally daily for 14 days modestly reduces alcohol craving scores and withdrawal scores when compared with placebo in adults with alcohol dependence that are undergoing withdrawal. Taking calcium carbonate did not reduce the need for diazepam; however, the study may have been inadequately powered to detect a difference between groups (107234).
• Atherosclerosis. It is unclear if oral calcium is beneficial for atherosclerosis. Details: A population study has found that taking calcium 1.2 grams daily for 3 years has no effect on carotid intima thickness or carotid atherosclerosis incidence. A total calcium intake (dietary and supplemental) of at least 1794 mg daily in older females may be associated with a decreased risk of carotid atherosclerosis when compared with a total calcium intake below 1010 mg daily (97351).
• Autism spectrum disorder. It is unclear if oral calcium during pregnancy is beneficial for reducing the odds of autism spectrum disorder in the offspring. Details: A small observational study found that calcium supplementation during pregnancy is associated with a 52% reduced odds of an autism spectrum disorder in the offspring (98900).
• Cancer. Oral calcium alone does not seem to prevent cancer. It is unclear if oral calcium with vitamin D is beneficial for preventing cancer. Details: Taking calcium alone does not seem to significantly reduce the risk of cancer (12118,15629). The role of calcium in cancer prevention when taken along with vitamin D is controversial, as conflicting results exist. One clinical trial shows that healthy postmenopausal females who take supplemental calcium 1400-1500 mg daily plus vitamin D3 (cholecalciferol) 1100 IU daily have a 60% lower relative risk for developing cancer of any type. Approximately 25 postmenopausal females would need to take this combination for 4 years to prevent one occurrence of cancer (15629). However, a more recent clinical study shows that healthy postmenopausal females who take supplemental calcium 1500 mg daily plus vitamin D3 (cholecalciferol) 2000 IU daily do not have a reduced risk of cancer at 4 years (93943). Reasons for the disparate results are not entirely clear. The discrepancies do not appear to be related to baseline vitamin D levels or different study populations. It is possible that, given the 10-year time lapse between the two publications, the discrepancies result from differences in cancer detection capability. Also, since cancer risk was a secondary outcome measure in the earlier study and a primary outcome measure in the more recent study, it is possible that the discrepancies result from differences in statistical methodologies. The effect of vitamin D and calcium on cancer risk in males and younger patients is not known. There is also interest in using calcium for reducing the risk of hematological malignancies. An analysis of the Women's Health Initiative study shows that taking calcium 1000 mg daily in combination with vitamin D3 400 IU for up to 10 years is associated with a 20% reduction in the risk of hematologic malignancies when compared with placebo. However, no effect on hematologic malignancy related mortality was seen (97354).
• Depression. It is unclear if oral calcium is beneficial for depression prevention. Details: Population research has found no association between a higher dietary intake of calcium and the risk of depression when compared with a lower dietary intake of calcium (96480).
• Diabetes. It is unclear if oral calcium is beneficial for type 2 diabetes prevention. Details: Some population research has found that a higher intake of calcium from diet or supplements, alone or in combination with vitamin D, is associated with a lower risk of developing type 2 diabetes when compared with lower calcium intake (14265,16713,96473). However, population research is often limited by confounding variables. For example, one analysis found that any beneficial effect might be influenced by concomitant magnesium intake (96473). Furthermore, other population research has found that serum calcium levels higher than 9.6 mg/dL are associated with greater risk of developing diabetes in Chinese adults with osteoporosis. This study is limited because it was not determined whether increased serum calcium was due to increased calcium intake or another factor such as parathyroid function (95815).
• Dysmenorrhea. It is unclear if oral calcium is beneficial for reducing pain associated with dysmenorrhea. Details: Clinical research shows that taking calcium carbonate 1000 mg with vitamin D 5000 IU daily for three menstrual cycles does not reduce pain when compared with placebo in patients with primary dysmenorrhea (95821). However, calcium carbonate 1000 mg taken alone seems to reduce pain when compared with placebo.
• Endometrial cancer. It is unclear if oral calcium is beneficial for endometrial cancer prevention. Details: A meta-analysis of population research suggests that calcium supplements may reduce the risk of endometrial cancer, but dietary calcium does not seem to have any effect (38893).
• Fall prevention. It is unclear if oral calcium with vitamin D is beneficial for preventing falls. Details: Research suggests that calcium in combination with vitamin D, but not calcium alone, might prevent falls by decreasing body sway and normalizing systolic blood pressure (6362,11939,39038). Some experts think the combination of calcium and vitamin D may be important (11916). Preliminary clinical research in adults residing in a health care facility shows that taking vitamin D supplements while increasing dietary calcium and protein for 2 years reduces falls by 11% when compared with standard diets. Intervention diets were supplemented with milk, yogurt, and cheese to provide calcium 1142 mg and protein 69 grams daily (107235). There might also be different effects in females compared to males. In one study, females aged 65 years or older who took vitamin D 700 IU plus calcium citrate 500 mg daily over a 3-year period had a 46% lower risk of falling. However, this combination did not decrease falls in males (14291).
• Fluorosis. Oral calcium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking calcium orally, in combination with ascorbic acid (vitamin C) and vitamin D, seems to be effective for reducing excessive fluoride levels in children and improving symptoms of fluorosis in children aged 6-12 years (990).
• Heart failure. It is unclear if oral calcium in combination with vitamin D is beneficial for preventing heart failure. Details: Based on a secondary analysis of a large-scale clinical trial (Women's Health Initiative), taking calcium 1000 mg with vitamin D 400 IU daily does not reduce the risk of heart failure in the overall population or in individuals at high risk. However, in a subgroup of postmenopausal females without risk factors for heart failure, calcium and vitamin D supplementation might reduce the risk of developing heart failure by about 37% (97307).
• Hypercholesterolemia. It is unclear if oral calcium is beneficial for hypercholesterolemia. Details: Some evidence shows that taking calcium carbonate 400 mg three times daily reduces low-density lipoprotein (LDL) cholesterol levels by 4% and increases high-density lipoprotein (HDL) cholesterol levels by 4% after 6 weeks of treatment when used in combination with a low-fat diet (American Heart Association Step 1) (2557). In contrast, a study in females with dyslipidemia shows that taking calcium 800 mg daily for 2 years might INCREASE total cholesterol levels by about 12 mg/dL when compared with placebo. This same study showed an association between calcium supplementation and an increase in total cholesterol levels and carotid intimal thickness in postmenopausal females, but not premenopausal females (97350). A recent meta-analysis of randomized controlled trials which included both healthy patients and patients with dyslipidemia shows that taking calcium 500-2000 mg daily and vitamin D 200-7142 IU daily modestly improves HDL cholesterol and triglyceride levels, but not LDL cholesterol levels, when compared with placebo. Subgroup analyses suggest that calcium and vitamin D supplementation is more effective in patients with dyslipidemia at baseline. It is unclear if this effect is due to calcium, vitamin D, or the combination (107227). However, other research shows that taking a specific supplement containing calcium 600 mg plus vitamin D 200 IU (Caltrate 600 D, Wyeth Consumer Healthcare Inc.) twice daily in combination with calorie restriction does not reduce total or LDL cholesterol levels when compared with placebo (15601).
• Lead toxicity. It is unclear if oral calcium is beneficial for reducing blood levels of lead. Details: Lead is mobilized along with calcium from bone during pregnancy and lactation, resulting in increased serum concentrations of lead. One clinical study suggests that calcium supplementation does not significantly decrease these elevated lead concentrations (1586). However, another clinical study suggests that taking calcium reduces blood lead levels by 11% when compared with placebo, with greatest effects observed in those with high baseline levels of lead (38957).
• Lyme disease. Although there is interest in using oral calcium for Lyme disease, there is insufficient reliable information about the clinical effects of calcium for this condition.
• Metabolic syndrome. It is unclear if oral calcium alone or with vitamin D is beneficial for metabolic syndrome prevention. Details: Population research has found that a higher intake of calcium from diet and supplements alone, or in combination with vitamin D, is associated with a lower risk of developing metabolic syndrome when compared with lower calcium intake (14265,16713).
• Nephrotic syndrome. It is unclear if oral calcium with vitamin D is beneficial for preventing nephrotic syndrome. Details: Clinical research shows that taking calcium 500-1000 mg daily for 3 months in combination with vitamin D3 60,000 IU daily or weekly for 4 weeks has no effect on bone mineral density or the risk of relapse in children with steroid-sensitive nephrotic syndrome (97355).
• Nonmelanoma skin cancer. It is unclear if oral calcium is beneficial for preventing keratinocyte carcinomas. Details: In middle aged and older adults recently diagnosed with a colorectal adenoma, clinical research shows that taking calcium 1200 mg daily as calcium carbonate for 3-5 years does not reduce the incidence of keratinocyte cancer when compared with placebo over a median of 8 years. A sub-group analysis shows that taking calcium alone or with vitamin D3 1000 IU daily reduced the risk of invasive cutaneous squamous cell carcinoma by a moderate amount, but had no effect on the risk of basal cell carcinoma (104622).
• Oral mucositis. When used in combination with fluoride treatments, a calcium phosphate mouth rinse seems to prevent and reduce mucositis-related pain in patients undergoing hematopoietic stem cell transplantation (HSCT). Details: A small clinical study in patients undergoing HSCT shows that using a particular mouth rinse (Caphosol, EUSA Pharma) containing calcium phosphate, in combination with fluoride treatments, reduces days of mucositis, the duration of pain, and the dose and days of morphine used when compared with placebo and fluoride treatment (38611).
• Ovarian cancer. It is unclear if oral calcium is beneficial for ovarian cancer prevention. Details: An older meta-analysis of 12 cohort studies found that dietary calcium intake is not associated with a reduced risk of ovarian cancer (38792). However, a more recent pooled analysis of 15 cohort and case-control studies has found that the highest intake of dietary or dairy calcium is associated with a 20% lower risk of ovarian cancer when compared to the lowest intake (97349).
• Postpartum depression. It is unclear if oral calcium is beneficial for reducing postpartum depression risk. Details: Preliminary clinical research shows that taking calcium 2 grams daily beginning at 11-21 weeks gestation reduces depression at 12 weeks postpartum when compared with placebo. However, no benefit is seen at 6 weeks postpartum (39447).
• Pregnancy-related leg cramps. It is unclear if oral calcium is beneficial for preventing leg cramps during pregnancy. Details: A small clinical study shows that taking calcium 1 gram twice daily (as a mixture of salts) for 2 weeks can reduce pregnancy-related leg cramps during the second half of pregnancy when compared with no treatment (2567).
• Prostate cancer. It is unclear if oral calcium is beneficial for prostate cancer prevention. Details: Some clinical research shows that taking calcium 1200 mg daily might decrease the risk of developing prostate cancer (14133). However, some epidemiological research suggests that consuming very high doses of calcium, over 2000 mg daily, might actually increase the risk of developing prostate cancer (14134). Some epidemiological research also suggests that doses greater than 1500 mg daily increase the risk of poorly differentiated, clinically advanced, and fatal prostate cancer (14132). Consumption of dairy products has also been weakly linked to a modest increase in risk of prostate cancer (98894). However, contradictory research suggests that there is no association between dietary intake of calcium and overall risk of prostate cancer (14131,14132,104630).
• Stroke. It is unclear if oral calcium is beneficial for stroke prevention. Details: Some population research has found that increasing dietary calcium intake is associated with a decreased risk of ischemic stroke (4822,38678). However, other population research has found that increasing dietary calcium intake is not associated with a decreased risk of stroke (91350). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years does not affect the risk of stroke when compared with control. However, the majority of the included research evaluated postmenopausal females, and it is unclear if this finding is applicable to other populations (107233).
• Vertigo. Oral calcium with vitamin D might reduce positional vertigo; the effect of calcium when used alone is unclear. Details: A large clinical study in adults with recurrent benign paroxysmal positional vertigo shows that taking calcium 500 mg and vitamin D 400 IU twice daily for one year reduces annual recurrence of vertigo by 27% when compared with no treatment. The number needed to treat to prevent vertigo was 3.7 (103681). It is unclear if this benefit is due to vitamin D, calcium, or the combination. More evidence is needed to rate calcium for these uses.

(Read more about CALCIUM)

POSSIBLY INEFFECTIVE

• Hyperlipidemia. A meta-analysis of small clinical studies suggests that consuming chia seeds, flour, powder, or oil for 7-24 weeks does not improve lipid levels in patients with conditions associated with hyperlipidemia. Details: A meta-analysis of 10 small clinical trials in patients with various metabolic conditions, including diabetes, metabolic syndrome, nonalcoholic fatty liver disease, and obesity, shows that consuming chia seeds, flour, or powder 15-60 grams daily for 7-24 weeks, or taking chia oil 6 grams daily for 8 weeks, does not reduce total cholesterol, low-density lipoprotein (LDL) cholesterol, or triglyceride levels or increase high-density lipoprotein (HDL) cholesterol levels when compared with control groups consuming wheat bran, oat bran, dietary fiber, poppy seeds, or soybean oil (106657). While the patient populations in the studies analyzed are more likely to develop hyperlipidemia, it is unclear if these findings can be generalized to patients diagnosed with hyperlipidemia.
• Obesity. Small clinical studies suggest that consuming chia seeds for up to 12 weeks does not reduce body weight in overweight or obese adults. Details: One small clinical study in overweight or obese individuals shows that ingesting chia seeds 25 grams mixed in 0.25 liters of water twice daily before meals for 12 weeks does not improve body composition or reduce blood pressure when compared with placebo (25533). Another small clinical study in overweight, postmenopausal females shows that ingesting milled or whole chia seeds 25 grams daily for 10 weeks does not improve body composition or blood pressure when compared to baseline (25532).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Athletic performance. It is unclear if oral chia is beneficial for improving athletic performance. Details: A small clinical study in trained athletes shows that drinking a beverage containing 50% of calories from chia seeds (Greens Plus Omega 3 Chia seeds) and 50% of calories from a carbohydrate-containing beverage (Gatorade) for 2 days prior to participating in an endurance exercise lasting more than 90 minutes leads to similar performance when compared with Gatorade alone (25531).
• Cardiovascular disease (CVD). Although there has been interest in using oral chia for CVD, there is insufficient reliable information about the clinical effects of chia for this purpose.
• Diabetes. Small clinical studies suggest that consuming chia for 4-6 months might reduce systolic blood pressure (SBP) in patients with type 2 diabetes, although it does not appear to improve glycemic control or lipid levels and has shown mixed effects on body weight and inflammatory markers. Details: One small clinical trial in patients with type 2 diabetes shows that consuming bread containing a specific, selectively bred type of chia (Salba, Salba Smart Natural Products LLC), providing 37 grams of chia daily for 12 weeks reduces SBP, C-reactive protein, and vonWillebrand factor, but not lipid levels, when compared with consuming bread containing wheat bran. This form of chia also significantly reduced glycated hemoglobin (HbA1c) when compared to baseline, but not when compared with a wheat bran control (16124). Another small clinical study in adults with type 2 diabetes and obesity shows that consuming Salba chia 40 grams daily, either baked into bread or as a powder, in conjunction with a restricted calorie diet for 6 months reduces weight by 1.6 kg and waist circumference by 2.8 cm when compared with an oat bran control. However, consuming chia had no effect on body fat percentage, HbA1c, or fasting glucose levels (97940). Also, a small clinical study in adults with type 2 diabetes shows that consuming chia seeds 40 grams daily for 12 weeks reduces SBP, but does not improve body weight, HbA1c, or levels of fasting glucose, lipids, or C-reactive protein, when compared with those not consuming chia (106658).
• Hypertension. It is unclear if oral chia is beneficial in patients with hypertension. Details: A very small clinical study in patients with mild hypertension shows that consuming chia flour 35 grams daily for 12 weeks reduces systolic blood pressure (SBP) by around 10 mm Hg and diastolic blood pressure (DBP) by almost 9 mm Hg when compared to baseline. In patients already taking antihypertensive drugs, chia seems to have an even greater impact on SBP and DBP. However, in patients not being treated with antihypertensive drugs, chia flour modestly reduces SBP by 6.5%, but does not significantly reduce DBP. No improvements in blood pressure were reported in patients consuming a wheat bran control (91516).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral chia is beneficial in patients with NAFLD. Details: Small, uncontrolled clinical studies in patients with NAFLD show that consuming milled chia seeds 25 grams daily for 8 weeks may reduce hepatic steatosis, as measured by the liver: spleen attenuation ratio, in up to 43% of subjects with prediabetes and 100% of subjects with diabetes when compared to baseline. Chia seed supplementation may also modestly reduce visceral fat, body mass index, and waist circumference in patients with prediabetes when compared to baseline, but does not seem to improve lipid levels (104530,110438). The validity of these findings is limited by the lack of a comparator group in both studies.
• Metabolic syndrome. Oral chia has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with metabolic syndrome shows that reducing daily caloric intake by 500 kcal and drinking a beverage containing chia seed 4 grams, soy protein 32 grams, dehydrated nopal 7 grams, and oat 22 grams daily for 2 months reduces body weight, body mass index, and waist circumference when compared to baseline, but not when compared with following a reduced calorie diet alone. However, following the reduced calorie diet and drinking this beverage appears to lower serum triglycerides and C-reactive protein and improve glucose tolerance when compared with a reduced calorie diet alone (25534). It is unclear if these findings are due to chia, other ingredients, or the combination.
• Muscle strength. It is unclear if oral chia is beneficial for increasing muscle strength and muscle mass during resistance training. Details: A very small clinical trial in healthy, non-resistance trained males shows that drinking a supplemental beverage containing chia flour 50 grams, providing 20 grams of protein and 3 grams of omega-3 fatty acids, is no more effective than whey protein 20 grams or placebo for augmenting the increases in muscle strength and fat-free mass that occur with an 8-week whole body resistance training program (112385). The habitual baseline diet of the study participants already contained dietary protein intakes recommended for strength training, and the beverage was only consumed three times per week immediately after training sessions.
• Pruritus. It is unclear if topical chia seed oil is beneficial in patients with pruritus. Details: One very small, uncontrolled clinical study in patients with xerotic pruritus or pruritus caused by kidney failure or diabetes shows that applying lotion containing chia seed oil 4% for 8 weeks improves skin hydration and reduces the severity of lichen simplex chronicus and prurigo nodularis when compared to baseline (25537). The validity of these findings is limited by the small study size and lack of a comparator group. More evidence is needed to rate chia for these uses.

(Read more about CHIA)

POSSIBLY EFFECTIVE

• Pregnancy-related iron deficiency. Oral chlorella, which contains iron, can help to prevent iron deficiency and anemia in pregnancy. Details: A small clinical study in Japanese patients in their first trimester of pregnancy shows that taking chlorella (Sun Chlorella A, Sun Chlorella Corp.) 2 grams three times daily, providing 7.2 mg iron daily, starting at the 12-18th week of gestation and continuing until delivery, reduces the incidence of maternal anemia, defined as a hemoglobin level less than 11 g/dL, to about 30%, compared with about 60% in patients receiving no intervention (95013).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Brain tumor. It is unclear if oral chlorella is beneficial in patients with glioma. Details: A small clinical study in patients with glioma shows that taking chlorella tablets plus chlorella liquid extract over 2 years might improve tolerability of chemotherapy and radiotherapy, but does not seem to affect tumor progression or survival, when compared to baseline (6804). The validity of this finding is limited by the lack of a comparator group.
• Depression. It is unclear if oral chlorella is beneficial as an adjunct to conventional antidepressant therapy in patients with major depressive disorder. Details: One open-label clinical trial in patients with major depressive disorder shows that taking chlorella extract tablets (ALGOMED, Bioprodukte Prof. Steinberg Produktions-und Vertreibs GmbH & Co.) 600 mg three times daily in addition to standard antidepressant therapy for 6 weeks improves subjective symptoms of depression and anxiety, measured on the Beck Depression Inventory II and the Hospital Anxiety and Depression Scale, when compared with standard antidepressant therapy alone (92132). The validity of this finding is limited by the large number of patients lost to follow-up and a lack of blinding.
• Dysmenorrhea. It is unclear if oral chlorella improves symptoms of dysmenorrhea. Details: A small clinical study in females 18-35 years of age with primary dysmenorrhea shows that taking chlorella (American Super Golden Med) 1500 mg daily for 8 weeks modestly decreases the severity and duration of painful menstrual cramps when compared with placebo (99882). This study is limited by small sample size and unclear allocation concealment.
• Exercise-induced respiratory infections. It is unclear if oral chlorella can prevent respiratory infections related to exercise. Details: A small clinical trial in physically active adults shows that taking chlorella (Sun Chlorella A, Sun Chlorella Corp.) 3 grams twice daily for 6 weeks increases salivary IgA, a marker of immune response, but doesn't improve the duration or severity of upper respiratory symptoms or reduce the risk for upper respiratory tract infections when compared with placebo (99881). However, this study was likely underpowered to detect differences in these outcomes.
• Fatigue. It is unclear if oral chlorella improves fatigue from exercise. Details: A small clinical trial in healthy males shows that taking chlorella (Chlorella Kogyo Co., Ltd) 2 grams three times daily for 4 weeks does not decrease exercise-induced fatigue or fatigue at rest when compared with placebo (99880).
• Fibromyalgia. It is unclear if oral chlorella improves symptoms of fibromyalgia. Details: A small open-label clinical trial in people with fibromyalgia shows that taking chlorella tablets (Sun Chlorella) 10 grams plus a liquid chlorella extract (Wakasa Gold) 100 mL daily for 2 months improves general symptoms and pain scores when compared with baseline (5890). The validity of this finding is limited by the lack of a comparator group.
• Halitosis. Although there is interest in using oral chlorella for halitosis, there is insufficient reliable information about the clinical effects of chlorella for this purpose.
• Hepatitis C. It is unclear if oral chlorella improves outcomes in patients with chronic hepatitis C infection. Details: A small clinical trial in patients with chronic hepatitis C virus (HCV) genotype 1 infection shows that taking chlorella tablets (Sun Chlorella A, Sun Chlorella Corp) 1500 mg twice daily for one week, then 1500 mg three times daily for 11 weeks, in addition to an extract containing 82 mg/mL of chlorella (Wakasa Gold, Sun Chlorella Corp) 30 mL twice daily for 12 weeks, decreases alanine aminotransferase (ALT) levels, but not aspartate aminotransferase (AST) or HCV RNA levels, when compared to baseline (92130). The validity of this finding is limited by the lack of a comparator group.
• Hyperlipidemia. It is unclear if oral chlorella reduces lipid levels. Details: A small clinical trial in patients with mild hypercholesterolemia, defined as total cholesterol between 200-250 mg/dL, who are not using lipid-lowering medications, suggests that taking chlorella (Daesang Corp.) 1664 mg three times daily for 4 weeks reduces total cholesterol by 1.6% and triglycerides by 10.3%, but does not affect low-density lipoprotein cholesterol or high-density lipoprotein cholesterol, when compared with placebo (92131). This study was limited by its short duration and small size.
• Hypertension. It is unclear if oral chlorella is beneficial in patients with hypertension. Details: Preliminary clinical research in patients with mild to moderate hypertension shows that taking chlorella 10 grams and chlorella extract 100 mL daily for 1-2 months does not reduce blood pressure when compared to baseline (41811).
• Metabolic syndrome. Although there is interest in using oral chlorella for metabolic syndrome, there is insufficient reliable information about the clinical effects of chlorella for this condition.
• Nonalcoholic fatty liver disease (NAFLD). Oral chlorella has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small open-label clinical trial in patients with NAFLD shows that taking chlorella extract 1200 mg with metformin 750 mg and vitamin E 200 mg daily for 3 months decreases alanine aminotransferase (ALT), aspartate aminotransferase (AST), and triglyceride levels when compared to baseline. Treatment with metformin 1250 mg and vitamin E 200 mg daily without chlorella does not appear to improve these outcome measures (99878). This study is limited by the lack of statistical comparison between groups.
• Peptic ulcers. Although there is interest in using oral chlorella for peptic ulcers, there is insufficient reliable information about the clinical effects of chlorella for this purpose.
• Pregnancy-induced hypertension. It is unclear if oral chlorella is beneficial for preventing pregnancy-induced hypertension. Details: A small clinical study in healthy Japanese patients in their first trimester of pregnancy shows that taking chlorella (Sun Chlorella A, Sun Chlorella Corp.) 2 grams three times daily, starting at the 12-18th week of gestation and continuing until delivery, reduces proteinuria and leg edema, but does not affect blood pressure, when compared with no intervention (95013). It is unclear if chlorella is beneficial in patients who are at risk for hypertension during pregnancy.
• Ulcerative colitis. Although there is interest in using oral chlorella for ulcerative colitis, there is insufficient reliable information about the clinical effects of chlorella for this condition. More evidence is needed to rate chlorella for these uses.

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POSSIBLY EFFECTIVE

• Constipation. Glucomannan is generally effective for treatment of constipation in adults, but the efficacy in children is less clear. Details: Clinical research in adults shows that taking glucomannan 1-1.5 grams three times daily orally for 3-5 weeks, sometimes followed by 1 gram twice daily for an additional 4 weeks, can relieve constipation. As a nonabsorbable dietary fiber, glucomannan appears to have a bulk laxative effect (11294,57783,57795,57816). Taking glucomannan 1.45 grams with lactulose 4.2 grams twice daily orally for 1-3 months appears to relieve constipation during pregnancy (57818). In children with constipation, glucomannan can increase the frequency of bowel movements but does not seem to improve stool consistency. A meta-analysis of 3 clinical trials including 122 children with functional constipation shows that glucomannan leads to 1.4 more stools per week but does not improve stool consistency when compared with placebo or a maltodextrin control (97935). Two studies included in this analysis show that taking a specific glucomannan supplement (Dicoplus, Dicofarm) 100 mg/kg once or twice daily (maximum daily dose 5 grams) along with fluids for up to 12 weeks relieves constipation in children (11295,57775). However, the other clinical study included in the analysis shows that taking a different glucomannan supplement (Dicoman Junior, Vitis Pharma) 1.26 grams twice daily for 4 weeks does not improve constipation in children (92005).
• Diabetes. Limited clinical research suggests that glucomannan may improve glycemic control and lipid profiles in patients with type 2 diabetes. Details: Taking glucomannan orally seems to reduce serum cholesterol and blood glucose levels in patients with type 2 diabetes (183,11357,11359,57791,57797,57798,112702). Most clinical research shows that a glucomannan dose of 3-15 grams daily for 4-12 weeks may reduce fasting blood glucose (183,11357,57791,57797,111225). Eating cookies containing glucomannan 0.5-0.7 grams per 100 kcal for 3 weeks has also been used (11358,11359,57797). Accordingly, a meta-analysis of 5 mostly small, low-quality clinical studies in adults with type 2 diabetes, that includes several of these studies, shows that taking glucomannan 1.2-15 grams daily for 4-16 weeks modestly improves fasting blood glucose when compared with placebo or wheat bran. This analysis also shows that taking glucomannan modestly improves 2-hour post-prandial glucose, total cholesterol, and low-density lipoprotein (LDL) levels but not triglycerides (112702). In healthy people, adding a specific glucomannan supplement (PolyGlycopleX, InovoBiologic Inc.) as granules, 2.5-7.5 grams before meals, or as capsules 3-6 grams with meals, can reduce the glycemic index of starchy foods (92003,92007). Also, taking this glucomannan product reduces postprandial glucose in a dose-dependent fashion in healthy people (92002,92007). However, the interpretation of this evidence is limited by low-quality research and variations in dosages and formulations.
• Hyperlipidemia. Most clinical research shows that glucomannan can reduce cholesterol levels in healthy people and those with hyperlipidemia. Details: Although some conflicting evidence exists (57794), most research shows that taking glucomannan orally can improve lipid levels in healthy adults, children and adults with hyperlipidemia, and adults with diabetes (178,11357,11358,11359,57779,57781,57784,57791,57799,97936)(112702). Meta-analyses of clinical research show that taking glucomannan 2.5-15.1 grams daily for up to 12 weeks can reduce total cholesterol by 19 mg/dL, low-density lipoprotein (LDL) cholesterol by 13-16 mg/dL, non-high-density lipoprotein cholesterol by 12 mg/dL, and triglycerides by 11 mg/dL when compared with a control (57797,97936). Clinical research has not demonstrated a dose-response relationship, and the most common glucomannan doses are 5-10 grams daily for up to 6 weeks for adults and 2-3 grams daily in divided doses for up to 8 weeks for children (11358,11359,57797,97936).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Dumping syndrome. It is unclear if oral glucomannan is beneficial in patients with dumping syndrome. Details: Preliminary clinical research shows that taking glucomannan (Propol, Pharmacia) 2.6 or 5.2 grams as a single dose reduces the incidence of reactive hypoglycemia following an oral glucose load in adult patients with previous gastric surgery (57805). Other preliminary clinical research shows that taking glucomannan improves glucose tolerance, but not glucose absorption, in children experiencing gastric dumping syndrome after gastric surgery (57804).
• Hypertension. It is unclear if oral glucomannan is beneficial in patients with hypertension. Details: Preliminary clinical research in patients with hypertension shows that eating cookies containing 0.7 grams of glucomannan per 100 kcal, for a total dose of up to 13 grams of glucomannan daily for 3 weeks, can lower systolic blood pressure by about 7% when compared with placebo (11359).
• Hyperthyroidism. It is unclear if oral glucomannan is beneficial in patients with hyperthyroidism. Details: Preliminary clinical research in patients with hyperthyroidism shows that taking glucomannan 1.3 grams twice daily orally, plus methimazole and propranolol for 2 months, reduces serum triiodothyronine (T3) and thyroxine (T4) levels during the first few weeks of therapy, when compared with methimazole and propranolol alone. However, these effects seem to diminish after 6 weeks of therapy (57793).
• Metabolic syndrome. It is unclear if oral glucomannan is beneficial for metabolic syndrome. Details: A small crossover study in adults with metabolic syndrome, defined as impaired glucose tolerance, reduced high-density lipoprotein (HDL) cholesterol, elevated serum triglycerides, and moderate hypertension, shows that consuming biscuits containing glucomannan 0.5 grams per 100 kcal (equivalent to approximately 8-13 grams/day) daily for 3 weeks may modestly improve fasting glucose, but does not improve blood pressure or levels of triglycerides or HDL cholesterol when compared with wheat bran biscuits (11358). However, the 2-week washout period between interventions may be too short to detect differences in some outcomes.
• Obesity. Although some low-quality research shows that oral glucomannan is beneficial for achieving slight improvements in body weight, other research does not support this. Details: Meta-analyses of clinical research on the use of glucomannan for improving body weight and body composition in adults and children with overweight or obesity show mixed results, with one analysis suggesting that taking glucomannan reduces body weight by around 0.8 kg when compared with placebo (57797), and another showing no improvement in body weight (92014). Reasons for these discrepant findings are not clear, but the discrepancies may relate to differences in the study populations and dosing and duration of glucomannan treatment, as well as the low methodological quality of many studies conducted to date. Similar to the pooled analyses described above, individual clinical study results are also mixed. Several small clinical studies show that taking glucomannan can improve body weight, body mass index (BMI), fat mass, and other measures of body composition in children and adults with overweight or obesity, usually when used in combination with a calorie-restricted diet (180,181,182,183,54240,92008,92010,92011,111224,112701). However, conflicting evidence exists (179,57784,57790,57796,92009,112430). Doses that have been used with positive outcomes in adults are 3-4 grams daily, taken in divided doses, for up to 3 months (181,182,183,92008,112701). In children, doses were 2-3 grams daily for 4 months (180). Specific products evaluated include Propylene TM (Natural Alternatives International), PolyGlycopleX (InovoBiologic, Inc.) 3-5 grams 2-3 times daily for 15 weeks, and. Chrombalance 338 mg before each meal and 226 mg in the afternoon daily for 5 weeks (54240,92010,92011). More evidence is needed to rate glucomannan for these uses.

(Read more about GLUCOMANNAN)

EFFECTIVE

• Anemia of chronic disease. Oral and intravenous iron in combination with erythropoiesis-stimulating agents (ESAs) are effective for treating anemia of chronic disease. Details: Iron supplementation with ESAs is effective for treating anemia associated with chronic kidney disease (CKD) or chemotherapy. During therapy with ESAs, iron levels should be monitored and supplementation provided as needed to ensure that the response is not limited by lack of iron for erythropoiesis (1087,1091,20110,20111,110192). Research shows that intravenous iron appears to be more effective than oral supplements for this purpose (20112,20113). In patients with CKD, intravenous iron at total doses from 2232 mg over 6 months to 1020 mg over one week increases hemoglobin levels more than oral doses of 4-6 mg/kg daily or 325 mg daily for up to 6 months (20112). Some research has evaluated the effect of intravenous or oral iron in patients not treated with ESAs. In patients with cancer or CKD, oral iron supplements have been shown to improve iron status (110184,110192). However, overall benefits of iron alone remain unclear in treated or untreated patients with cancer and more research is needed to rule out an increase in mortality and to determine any effect on blood transfusion requirements (110192). Preliminary clinical research shows that children aged 6 months to 10 years with HIV and anemia who take elemental iron 3 mg/kg daily along with a multivitamin for 3 months have a 41% lower chance of having persistent anemia at 3 months when compared with multivitamins alone (95432).
• Iron deficiency anemia. Oral and intravenous iron are effective for treating or preventing iron deficiency anemia. The benefits of iron supplementation in people with iron deficiency without anemia are unclear. Details: Oral iron supplements, mainly as ferrous sulfate, are effective for treating and preventing iron deficiency anemia in adults, children, and infants (1089,7135,17495,17496,17497,103806,20114,20115,91183,96621)(104680,104681,112601). Other forms are also effective, including sodium iron ethylenediaminetetra-acetate (NaFeEDTA), iron(III)-hydroxide polymaltose complex (IPC), iron protein succinylate, iron bisglycinate, and lactoferrin with iron (20117,20118,110189). Treatment with iron supplements should increase hemoglobin levels by 1 gram/dL every 2-3 weeks. However, even after hemoglobin has normalized, it may take up to 4 months for iron stores to be replenished (17497). Historically, treatment of iron deficiency anemia with oral iron supplements has typically consisted of a daily dosing regimen, often taken in divided doses to reduce adverse effects. In more recent years, however, intermittent iron supplementation (1-3 doses/week) has become preferred for some patients, particularly those with mild anemia, due to better absorption and a possible reduction in side effects compared to daily dosing. One small clinical study shows that taking ferrous sulfate 60 mg on alternate days in single doses improves iron absorption when compared to once daily dosing (96630). Another small clinical study in females with iron-deficiency anemia shows that fractional iron absorption is 40% to 50% higher with alternate-day dosing compared with daily dosing. Furthermore, total iron absorption was shown to be similar for alternate day dosing of elemental iron 200 mg compared with daily dosing of 100 mg, but the incidence of gastrointestinal adverse effects may be lower for the alternate day dosing regimen (101514). A meta-analysis of 25 clinical trials, including 10,996 menstruating females with or without pre-existing iron deficiency and/or anemia, shows that intermittent iron reduces the risk of anemia and increases hemoglobin and serum ferritin when compared with placebo or no intervention. This meta-analysis did not identify differences in the risk of anemia, hemoglobin, or serum ferritin between intermittent and daily iron supplementation. However, it did show that females receiving intermittent dosing had a 59% reduction in the risk for adverse effects. The validity of these findings is limited by significant heterogeneity in the enrolled populations and selected dosing strategies, including frequency of intermittent dosing, total weekly dose, and duration of follow-up. In addition, the subgroup analyses performed by baseline anemia, hemoglobin, and serum ferritin, as well as duration of follow-up, showed differing overall conclusions when comparing intermittent and daily iron supplementation. While intermittent dosing appears to be beneficial when compared with daily dosing for some patients with iron deficiency anemia, intermittent dosing may be less effective than daily iron supplementation in some patients (103806). For patients with severe anemia, twice daily dosing may be preferred to alternate day dosing due to faster response. A small clinical study in patients with iron deficiency anemia shows that taking ferrous sulfate 200 mg twice daily is more effective at increasing hemoglobin levels by 3 weeks when compared with ferrous sulfate 400 mg taken on alternate days in single doses (102864). Intermittent iron supplementation has also been investigated in children. A meta-analysis of clinical research in children and adolescents with or without pre-existing iron deficiency and/or anemia shows that taking iron supplements 1-2 times weekly is similarly effective as 3-7 times weekly for decreasing iron deficiency and iron deficiency anemia. However, ferritin and hemoglobin levels increased to a greater extent with 3-7 times weekly supplementation (112601). Blood transfusion may be required for some patients with severe iron deficiency anemia who have symptoms such as dyspnea and fatigue (17497). Intravenous iron should be considered in patients who cannot tolerate oral iron or in patients with chronic bleeding or intestinal malabsorption (17497). Guidelines from the British Society of Gastroenterology recommend treatment with iron while awaiting investigations to rule out gastrointestinal issues in adults in the absence of an alternative explanation. The guidelines recommend ferrous sulfate, fumarate, or gluconate as one tablet daily. If adverse effects occur, intake can be reduced to once every other day, or alternative oral or parenteral sources of iron can be used. Parenteral sources should be used if oral sources are contraindicated or ineffective. Treatment should be monitored and continued after hemoglobin levels are normalized (110193). Iron supplementation may also be beneficial in patients with iron deficiency without anemia, which can cause fatigue and reduced well-being, although guidelines are lacking. A meta-analysis of randomized controlled trials in adults with iron deficiency but not anemia shows that supplemental iron improves iron stores and hemoglobin levels. In addition, iron moderately reduces self-reported fatigue, but not physical capacity, when compared with placebo. Oral ferrous sulfate was used in most studies included in the analysis; however, intravenous or intramuscular iron were also used (104684).
• Pregnancy-related iron deficiency. Oral iron is effective for preventing pregnancy-related iron deficiency. Details: Clinical research shows that taking iron orally at an average daily dose of 20-225 mg of elemental iron increases maternal hemoglobin levels by up to 1 gram/dL when compared with placebo and reduces the risk of maternal anemia by 62% to 100% (20122,20123,20124,110180,110188). Some clinicians may recommend alternating days of iron administration to reduce gastrointestinal adverse effects. A pooled analysis shows that taking iron supplements on alternating days during pregnancy maintains adequate iron intake and reduces gastrointestinal adverse effects when compared with taking iron daily (96625). Various forms of oral iron seem to be equally effective for raising hemoglobin levels (110185,110188). However, in patients with anemia during pregnancy, a meta-analysis of clinical research shows that intravenous iron sucrose and ferric carboxymaltose were more effective than oral ferrous sulfate for improving hemoglobin levels (110185).

POSSIBLY EFFECTIVE

• Breath-holding attacks. Oral iron seems to be effective for reducing the frequency of breath-holding attacks in children with iron deficiency. Details: The incidence of breath-holding attacks is increased in children with iron deficiency or iron deficiency anemia. Most research shows that oral supplementation with ferrous sulfate 3-6 mg/kg daily for 4-16 weeks reduces the frequency of breath-holding attacks in children aged 1-72 months (20128,104682,104683). The best evidence comes from a meta-analysis of one randomized controlled trial and 11 observational single arm studies (104682). In this analysis, approximately 84% of children experienced at least a 50% decreased frequency of breath-holding attacks (104682). Some preliminary clinical research also shows that administering intramuscular iron reduces the frequency of breath-holding attacks and increases remission in children with iron deficiency anemia (20128).
• Cognitive function. Oral iron seems to be effective for improving cognitive function in children and adolescents with iron deficiency. Details: Taking iron orally seems to improve cognitive function in iron-deficient children and adolescents (20121,112600). For example, ferrous sulfate 650 mg twice daily for 8 weeks improved verbal learning and memory in non-anemic iron-deficient adolescent females (1095). Ferrous sulfate 50 mg twice weekly for 16 weeks appeared to improve attention measures in adolescent females with possible anemia (91186). Iron also appears to reverse developmental and learning deficits caused by iron-deficiency in anemic infants (1104). Some clinical research is focused on children and adolescents from low- and middle-income countries. In children aged 5-19 years with or without iron-deficiency anemia, a meta-analysis of clinical research shows that iron supplementation for 3-8 months dose-dependently improves measured intelligence by a modest amount. However, there was no effect on other measures of cognition, including attention or memory (110181). Another meta-analysis of clinical research in school age children shows that taking iron for 2-12 months modestly improves intelligence, attention, and memory, but not educational achievement, when compared with placebo or no intervention. However, sub-analyses show that any benefits are limited to children with anemia (112600).
• Heart failure. Intravenous iron seems to be effective for improving recovery in patients with heart failure and iron deficiency. It is unclear if oral iron is effective. Details: Iron deficiency is common in patients with heart failure (17499,112597,112598,112599). Individual clinical trials and meta-analyses of clinical research in patients with heart failure show that administering intravenous iron, as ferric carboxymaltose, iron dextran, iron isomaltoside, or iron sucrose, for at least 12 weeks modestly improves quality of life, increases exercise capacity, and reduces hospitalizations when compared with placebo or standard care. However, there was no effect on all-cause mortality or cardiovascular mortality (17498,91179,110176,110187,112597,112598,112599). Some individual clinical trials have used intravenous ferric carboxymaltose 200 mg or iron sucrose 200 mg in patients with mild or moderate heart failure and iron deficiency (17498,91179). Guidelines from the British Society of Gastroenterology suggest that treatment with parenteral iron improves symptoms and quality of life in patients with functional iron deficiency related to CHF (110193). Limited research has investigated the effect of oral iron in this population. A small meta-analysis of clinical research shows with low certainty that taking iron orally has beneficial effects on serum ferritin and left ventricular ejection fraction (110178). Most research shows that taking oral iron does not improve hemoglobin levels, quality of life, or exercise capacity when compared with placebo (100970,110178). However, one small clinical trial shows that taking oral iron modestly improves iron status and overall symptoms and increases the 6-minute walking distance by about 46 meters, compared with a reduction of only 14 meters in those taking placebo (110183). Some doses used in individual clinical studies have included iron polysaccharide 150 mg twice daily for 16 weeks and ferrous sulfate 200 mg three times daily for 12 weeks (100970,110183).
• Restless legs syndrome (RLS). Oral and intravenous iron seem to be beneficial for RLS. The American Academy of Neurology recommends a combination of oral ferrous sulfate and vitamin C or intravenous ferric carboxymaltose for patients with RLS. Details: RLS is commonly associated with iron deficiency anemia. Some clinical research shows that taking iron in the form of ferrous sulfate 325 mg twice daily for 12 weeks reduces RLS symptoms comparably to pramipexole. Symptoms such as leg discomfort, need to move, and sleep disturbances improved considerably in about half of the patients taking either treatment (91181). Additional clinical research shows that taking ferrous sulfate 325 mg twice daily along with vitamin C 100 mg twice daily for 12 weeks reduces symptoms of RLS when compared with vitamin C alone in patients with RLS and low-normal serum ferritin levels (94189). Based on these results, clinical practice guidelines by the American Academy of Neurology report that taking this combination of oral ferrous sulfate and vitamin C is likely to improve symptoms in patients with RLS and low-normal serum ferritin (93587). Intravenous iron may also reduce symptoms of RLS. Clinical practice guidelines by the American Academy of Neurology report that two doses of intravenous ferric carboxymaltose 500 mg given 5 days apart are likely to improve symptoms and quality of life within 28 days in patients with moderate to severe RLS, regardless of serum ferritin levels. Intravenous iron sucrose has also been evaluated in patients with RLS, but there is currently insufficient available evidence to support or refute the use of this form of iron for treating RLS (93587).

POSSIBLY INEFFECTIVE

• Athletic performance. Oral iron does not seem to improve athletic performance. Details: A meta-analysis of clinical research in adults of childbearing age shows that iron supplementation improves some exercise performance measures, such as maximal oxygen uptake capacity, but not others, such as time until exhaustion and energy consumption, when compared with control (91184). Another meta-analysis of clinical research in patients with iron deficiency without anemia shows that iron supplementation improves subjective measures of fatigue, but does not improve exercise time to exhaustion or other measures of physical capacity (104684). A small clinical study in healthy children shows that taking iron supplements or consuming food providing iron 30-200 mg daily for 1-2 months improves running performance when compared with placebo. This was demonstrated by reductions of heart rate of 6.6 to 8 beats per minute during the running exercise. One preliminary study included in this analysis also showed that iron supplementation improved treadmill endurance time (20140).
• Child growth. Oral iron does not seem to be beneficial for child growth. Details: Meta-analyses of mainly preliminary clinical research show that oral iron supplementation, at doses averaging 2-80 mg or 1-10 mg/kg elemental iron daily for up to 52 weeks, does not increase growth rate in children (20131,20132,20133,95434).
• Preterm labor. Oral iron does not seem to prevent preterm labor and may actually increase the risk in malaria-endemic regions. Details: A meta-analysis of results from five clinical studies shows that maternal intake of iron as ferrous sulfate 20-60 mg daily for 14-26 weeks starting in the second trimester of pregnancy does not affect the length of gestation or increase birthweight of the infant (95434). In females from a malaria-endemic area who have never been pregnant before, another clinical study shows that taking ferrous gluconate 60 mg and folic acid 2.8 mg weekly, starting before conception and continuing to the first antenatal visit, may more than double the risk of preterm birth, defined as a delivery under 37 weeks gestation, when compared with folic acid alone (100969). Some research suggests that the adverse outcome in this latter study may be explained by a rise in hepcidin levels in pregnant patients with malaria. Hepcidin is a hormone that regulates iron absorption and distribution, and malaria can upregulate hepcidin. High levels of hepcidin can decrease iron absorption, stimulate inflammatory processes, and cause progesterone withdrawal, leading to preterm labor (102863).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• ACE inhibitor-induced cough. It is unclear if oral iron is beneficial in patients with this condition. Details: A small clinical trial shows that taking ferrous sulfate 256 mg daily reduces or eliminates cough induced by ACE inhibitors such as captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), and others, when compared with placebo (7307).
• Androgenic alopecia. Oral iron has only been evaluated in combination with other ingredients, its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with androgenic alopecia or telogen effluvium shows that taking one tablet daily of a specific product (GFM Oral, Cantabria Labs), providing an unknown dose of iron in combination with selenium, taurine, cysteine, methionine, and hydrolyzed collagen, along with conventional therapy, consisting primarily of finasteride or minoxidil, for 12 weeks improves hair loss when compared with conventional therapy alone (111636). It is unclear if this effect is due to iron, other ingredients, or the combination.
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral iron is beneficial in children with ADHD. Details: Three small clinical studies in children with ADHD and iron deficiency shows that taking oral iron improves some measures of ADHD after 1-3 months of treatment when compared with baseline or placebo. These studies used ferrous sulfate 5 mg/kg daily, ferrous sulfate 80 mg daily, ferrous fumarate 200 mg daily for children weighing up to 30 kg, or ferrous fumarate 400 mg daily for children weighing more than 30 kg (1093,16013,110191).
• Child development. It is unclear if oral iron is beneficial for improving development in non-anemic children. Details: Some observational research has found that iron deficiency in infancy is associated with poor verbal performance and social skills in childhood (102862). It is unknown whether iron supplementation can ameliorate these developmental issues. In non-anemic infants and children, preliminary clinical research shows that iron does not improve cognitive performance; the evidence for the benefits of iron on psychomotor development is conflicting (20129,20130,91315,96616,96626).
• Esophageal cancer. It is unclear if oral iron is beneficial for esophageal cancer prevention. Details: Population research has found that taking iron supplements is associated with a 32% lower risk of esophageal adenocarcinoma when compared to never taking iron supplements. However, use of iron supplements is not associated with a lower risk of esophageal squamous cell carcinoma (95435).
• Fatigue. It is unclear if oral iron is beneficial in patients with fatigue due to iron deficiency without anemia. Details: A meta-analysis of mainly preliminary clinical research in adults with iron deficiency without anemia shows that iron reduces self-reported fatigue moderately more than placebo (104684). A specific ferrous sulfate supplement (Tardyferon; Pierre Fabre Médicament) providing 80 mg of elemental iron daily for 4-12 weeks was used in two studies included in this analysis (11406,91188).
• Inflammatory bowel disease (IBD). In patients with active IBD, intravenous iron may be more beneficial than oral iron due to impaired absorption. However, it may also increase the risk of infection in these patients. Details: Since the absorption of oral iron may be impaired in patients with active symptoms of IBD, guidelines from the British Society of Gastroenterology suggest that treatment with parenteral iron may be needed in patients with IBD who have moderate to severe iron-deficiency anemia (110193). However, a meta-analysis of clinical research in this population shows that administering IV iron, usually as iron sucrose or ferric carboxymaltose, increases the risk of infection by 73% when compared with oral iron or no iron (110186).
• Postoperative recovery. It is unclear if intravenous iron is beneficial for recovery following cardiac surgery. Details: A meta-analysis of low- to moderate-quality clinical research in patients with preoperative iron-deficiency anemia shows that treatment with intravenous iron before cardiac surgery does not improve the rate of transfusions or the length of stay in the intensive care unit or hospital when compared with control groups, including placebo, oral iron, or no treatment. Also, a meta-analysis of clinical research shows that intravenous iron does not reduce postoperative mortality rates (110182).
• Postpartum depression. Although there has been interest in using iron for postpartum depression, there is insufficient reliable information about the clinical effects of iron for this condition.
• Prematurity. Enteral iron seems to be beneficial for some measures of development in preterm infants. Details: A meta-analysis of clinical research in preterm or low birthweight infants fed human milk shows that enteral iron supplementation increases linear growth and reduces the risk of anemia when compared with control groups receiving no iron supplementation. However, there was no effect on serum ferritin, weight, head circumference, cognitive development, risk of infection, or risk of necrotising enterocolitis (110177). Additional clinical research in infants born at 24-28 weeks' gestation shows that a higher average enteral iron dose by 60 days of age is positively associated with cognitive performance at 2 years of corrected age. However, this association was not present for iron doses received at 90 days of age (110190). More evidence is needed to rate iron for these uses.

(Read more about IRON)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Diabetes. Although there has been interest in using oral pea protein for diabetes, there is insufficient reliable information about the clinical effects of pea protein for this purpose.
• Exercise-induced muscle damage. It is unclear if oral pea protein is beneficial for exercise-induced muscle damage. Details: A small clinical study in healthy, untrained males shows that taking a specific type of pea protein (Nutralys S85 Plus, Roquette) 0.3 grams/kg 3 times daily for 5 days after a 90-minute whole-body high-intensity eccentric exercise bout does not reduce surrogate markers of exercise-induced muscle damage, including creatine kinase, lactate dehydrogenase, and myoglobin, when compared with whey protein or water (104758). However, the study may have been inadequately powered to detect a difference between groups and is further limited by double-blinding restricted only to the protein supplements. The water control did not match the taste, texture, or calorie content of the protein supplements. Another small clinical trial in healthy, physically active older adults shows that taking pea protein 25 grams daily for 10 days prior to and 3 days after a single 20-30 km endurance walk does not improve markers of muscle damage when compared with placebo and may be less effective when compared with whey protein (111729).
• Exercise-induced muscle soreness. It is unclear if oral pea protein is beneficial for exercise-induced muscle soreness. Details: A small clinical study in healthy, untrained males shows that taking a specific type of pea protein (Nutralys S85 Plus, Roquette) 0.3 grams/kg 3 times daily for 5 days after a 90-minute whole-body high-intensity eccentric exercise bout does not reduce exercise-induced muscle soreness when compared with whey protein or water (104758). However, the study may have been inadequately powered to detect a difference between groups and is further limited by double-blinding restricted only to the protein supplements. The water control did not match the taste, texture, or calorie content of the protein supplements. Another small clinical trial in healthy, physically active older adults shows that taking pea protein 25 grams daily for 10 days prior to and 3 days after a single 20-30 km endurance walk does not improve muscle soreness when compared with whey protein or placebo (111729).
• Hyperlipidemia. Although there has been interest in using oral pea protein for hyperlipidemia, there is insufficient reliable information about the clinical effects of pea protein for this purpose.
• Hypertension. It is unclear if oral pea protein hydrolysate is beneficial for hypertension. Details: A small clinical study in adults with elevated blood pressure shows that taking a pea protein hydrolysate 3 grams daily for 3 weeks reduces systolic blood pressure by 6 mmHg when compared with placebo. Taking the same product at a dose of 1.5 grams daily does not reduce blood pressure (94973).
• Irritable bowel syndrome (IBS). Oral pea protein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small open-label study in patients with diarrhea-predominant IBS shows that taking two tablets of a specific product (Gelsectan, Noventure) containing pea protein, grape seed extract tannins, xyloglucan, and xylo-oligosaccharides (doses unknown) before breakfast and dinner daily for 6 months improves IBS-related symptoms, including diarrhea, pain, bloating, defecatory frequency, stool consistency, and defecatory urgency when compared to baseline (108881). The validity of this study is limited by a lack of placebo control group.
• Muscle strength. Clinical research on the impact of oral pea protein on muscle strength is mixed. Its effects might be similar to whey protein. Pea protein may be more effective in individuals with lower baseline muscle strength. Details: A clinical trial in physically active, but non-resistance trained, young male adults participating in a 12-week upper body resistance training program shows that taking a specific type of pea protein isolate (Nutralys, Roquette) 25 grams twice daily over the training program does not augment training-induced increases in muscle thickness or strength when compared with whey protein or isocaloric placebo. However, a post hoc analysis of participants with the lowest muscle strength at baseline shows that pea protein supplementation increases bicep muscle thickness more than placebo and to a similar degree as whey protein (95426). Additionally, a very small clinical study in trained adults shows that taking pea protein 24 grams twice daily during an 8-week high-intensity functional training program improves muscle strength to a similar degree as whey protein, while neither supplement appears to impact muscle thickness or body mass (102013). The small study size and lack of an isocaloric, protein-free control limits conclusions that can be drawn from this study.
• Obesity. Although there has been interest in using oral pea protein for obesity, there is insufficient reliable information about the clinical effects of pea protein for this purpose.
• Postoperative recovery. Oral pea protein has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults undergoing gastrointestinal resection due to cancer shows that consuming a beverage (Providextra, Fresenius Kabi) containing pea protein hydrolysate 11% and carbohydrates 89% the night before (400 mL) and the morning of surgery (200 mL) reduces postoperative hospital stay by almost 2-fold when compared with conventional preoperative fasting (94933). It is unclear if these findings are due to pea protein, carbohydrates, or the combination. More evidence is needed to rate pea protein for these uses.

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EFFECTIVE

• Hypokalemia. Oral or intravenous potassium can treat and prevent hypokalemia. Details: Administering potassium orally or intravenously is effective for treating and preventing hypokalemia (15,107970). Oral potassium 20 mEq (780 mg of elemental potassium) is typically taken once daily to prevent hypokalemia (15,95010). Oral potassium 40-100 mEq (1560-3900 mg of elemental potassium) is typically taken in 2-5 divided doses daily to treat hypokalemia (95010). Doses should be limited to 40 mEq (1560 mg of elemental potassium), and the total dose should not exceed 200 mEq (7800 mg of elemental potassium) in 24 hours (95010). Potassium supplementation and route of administration should be individualized based on serum potassium level and patient status (15,107970).

LIKELY EFFECTIVE

• Hypertension. Oral potassium, via dietary intake or supplementation, reduces blood pressure. Details: Population research has found that higher dietary potassium consumption is associated with a lower risk of developing hypertension (1310,8817,69512). Additionally, most clinical research shows that potassium, taken orally as part of the diet or as a supplement, reduces systolic blood pressure by about 3-9.5 mmHg and diastolic blood pressure by about 2-6.4 mmHg in patients with or without hypertension (3385,92104,92106,95624,107974). In most of these studies, daily intake of potassium typically ranged from about 1500-7800 mg, with the most common intake being about 2340-2540 mg daily (92104,95624). However, some research shows that taking potassium does not lower systolic or diastolic blood pressure (69541,69550,107966). Differences in the patient populations, potassium intake, and salt intake could have contributed to the conflicting results. Potassium seems to be more effective for people with hypertension, low potassium levels, high daily sodium intake, and for Black adults (3384,3385,3386,92104,92106). Some research also shows that the greatest blood pressure-lowering effects of potassium occur at doses of about 3900-7800 mg daily (95624). A meta-analysis of clinical trials using a novel computational technique to assess both potassium intake and excretion suggests that the optimal blood pressure reduction occurs when taking about 1500 mg supplemental potassium daily or an overall intake of 4500-6500 mg potassium daily (105448). This analysis is limited by the heterogeneity and short duration of the included trials. There is also interest in utilizing low-sodium, high-potassium food substitutes to treat hypertension. Research shows that using salt substitutes containing 25% to 30% potassium chloride reduces systolic and diastolic blood pressure by 3-4.6 mmHg and 1 mmHg, respectively, when compared with regular table salt (107971,107976). In 2017, the American College of Cardiology and the American Heart Association (ACC/AHA) published guidelines recommending that patients with hypertension consume 3500-5000 mg of potassium daily (95680). This intake of potassium is expected to lower systolic blood pressure by about 4-5 mmHg in patients with hypertension and by about 2 mmHg in normotensive patients (3385). Although potassium supplements and dietary potassium both seem to be beneficial, the guidelines recommend getting potassium from dietary sources, since potassium-rich diets are usually heart-healthy (95680). Additionally, the US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).
• Kidney stones (nephrolithiasis). Oral prescription potassium citrate reduces the risk of kidney stone recurrence. It is unclear if non-prescription potassium citrate would be beneficial. Details: The American Urological Association (AUA) recommends potassium citrate therapy for patients with recurrent calcium stones and low urinary citrate, those with recurrent calcium or calcium oxalate stones without current metabolic abnormalities, and those with uric acid or cystine stones. The citrate component reduces urine calcium excretion and increases urine citrate and urine pH, which in turn alleviates crystal growth, formation, and aggregation. Sodium citrate may also be used to prevent stone recurrence; however, due to sodium's propensity to increase urine calcium excretion, potassium citrate remains the preferred salt formulation (107972). It is important to note that potassium citrate supplements are not equivalent to prescription potassium citrate products. Dose and duration of treatment is determined by a healthcare professional and individualized based on a patient's urinary citrate levels (107975,107989). Serum potassium levels should be monitored prior to starting potassium citrate, within 2 weeks of treatment initiation, and every 12 months (107975).

POSSIBLY EFFECTIVE

• Cardiovascular disease (CVD). Eating foods high in potassium and low in sodium might reduce the risk of cardiovascular disease. It is unclear if taking potassium supplements has the same benefit. Details: Large population studies in adults without prior CVD have found that higher dietary potassium intake is associated with a lower risk of cardiovascular events (109395,109399). One study found that daily potassium intake of about 3300 mg is associated with a 13% reduction in CVD risk when compared with intake of about 1920 mg (109399). The other study found that each additional 1000 mg of daily urinary potassium excretion, which is a marker of dietary intake, is associated with an 18% reduction in CVD risk (109395). Another observational study in over 15,000 adults with history of stroke or hypertension shows that replacing regular table salt with a substitute product containing 75% sodium chloride and 25% potassium chloride for an average of 5 years decreases the rate of stroke, major cardiovascular events, or death (107976). High quality clinical trials are needed to confirm this association. The US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).
• Stroke. Eating foods high in potassium and low in sodium might reduce the risk of stroke. It is unclear if taking potassium supplements has the same benefit. Details: Higher dietary intake of potassium seems to be associated with a lower risk of stroke. Population research has found that increasing dietary potassium intake by 1-1.5 grams daily is associated with up to a 20% reduced risk of stroke (92105,92107). Some population research has found that higher supplemental intake of potassium is associated with a 29% reduced risk of ischemic stroke. However, supplemental potassium intake is not found to be associated with a lower risk of hemorrhagic or total stroke (92107). An observational study in over 15,000 adults with history of stroke or hypertension shows that replacing regular table salt with a substitute product containing 75% sodium chloride and 25% potassium chloride for an average of 5 years decreases the rate of stroke, major cardiovascular events, or death (107976). High quality clinical trials are needed to confirm this association. The US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Dental hypersensitivity. It is unclear if topical potassium improves dental hypersensitivity. Details: One meta-analysis of clinical research shows that using a dentifrice containing 5% potassium nitrite reduces dentin sensitivity when compared with a dentifrice that does not contain potassium nitrite (69549). Other clinical research published in a systematic review shows that potassium-containing toothpastes might reduce dentin sensitivity more than controls that do not contain potassium. However, these toothpastes might be less effective than other active toothpastes, such as those containing sodium monofluorophosphate, and the effect may result from a placebo effect, since the mechanism of action of potassium is unclear (69456).
• Diabetes. It is unclear if increasing dietary potassium reduces the risk of diabetes. Details: A meta-analysis of 7 large population studies has found that consuming dietary potassium 3300-3500 mg daily is associated with a 20% reduction in the risk of diabetes when compared with consumption below 1000 mg daily. Results were similar when studies that measured potassium intake with a dietary questionnaire were analyzed separately from those that measured intake based on urinary potassium excretion (110776). However, the validity of this finding is limited by the heterogeneity of the included studies. Furthermore, despite use of data from various databases, most studies included in the analysis were conducted by the same author.
• Impaired glucose tolerance (prediabetes). It is unclear if oral potassium improves glycemic control in prediabetes. Details: A small clinical study in Black patients with prediabetes shows that taking extended-release potassium (Klor-Con M10, Cardinal Health) 40 mEq daily as potassium chloride for 3 months does not improve glucose tolerance when compared with placebo. Although fasting glucose levels were slightly reduced in the potassium group when compared with placebo, both groups experienced a worsening of glucose intolerance, with no change in insulin levels or glycated hemoglobin (98533).
• Osteoporosis. Although there is interest in using oral potassium for osteoporosis, there is insufficient reliable information about the clinical effects of potassium for this condition.
• Physical performance. It is unclear if oral potassium improves physical performance in older adults. Details: Observational research in older adults has found that decreased dietary potassium intake and increased dietary sodium intake over 5 years is associated with worsened physical performance (105450).
• Systemic lupus erythematosus (SLE). It is unclear if oral potassium is beneficial in patients with SLE. Details: Observational research in patients with SLE has found that increased dietary potassium intake is not associated with improvements in disease activity scores or markers of cardiovascular disease, including lipid levels and blood pressure, when compared with low dietary potassium intake. However, higher potassium intake does seem to reduce the odds of having elevated levels of C-reactive protein, a marker of inflammation, in these patients (109397). More evidence is needed to rate potassium for these uses.

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POSSIBLY EFFECTIVE

• Benign prostatic hyperplasia (BPH). Taking oral pumpkin seed or pumpkin seed oil may improve symptoms of BPH. Details: One study in patients with BPH shows that taking pumpkin seed 5 grams twice daily for 12 months may be more effective for controlling symptoms than pumpkin seed extract 1000 mg twice daily (92383). A specific pumpkin seed extract (Prosta Pink Forte) 1-2 capsules daily for 12 weeks has also been used (11231). Some preliminary clinical research also suggests that taking pumpkin seed oil (Prostafit, EuRho Vital) two tablets daily for 6 months may be as effective as the medication prazosin (92382). Pumpkin seed oil has also been compared with tamsulosin. A clinical study comparing pumpkin seed oil 360 mg twice daily to tamsulosin 0.4 mg once nightly for 3 months shows that both treatment groups report improvements in BPH symptoms and quality of life when compared with baseline, although improvement appears greater in the tamsulosin group, specifically when measured at 1 month and 3 months. In the pumpkin seed oil group, adverse effects were reported in 0% of patients, compared with 15% of patients taking tamsulosin (107842). The validity of this study is limited due to the short duration of treatment. Pumpkin seed oil or extracts have also been studied in combination with saw palmetto (6777), with saw palmetto, nettle root, and lemon extracts plus beta carotene (5093), and with saw palmetto, small flowered willow herb, lycopene, and pygeum (92379).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Androgenic alopecia. Oral pumpkin seed oil might improve hair regrowth in males with mild to moderate hair loss. Details: Clinical research in males with mild to moderate hair loss shows that taking pumpkin seed oil (Octa Sabal Plus, Dreamplus Co. Ltd.) 400 mg daily in divided doses for 24 weeks increases hair count by 30% when compared with placebo. Self-rated improvement and satisfaction scores were 62% and 52% with pumpkin seed oil and placebo, respectively (92378). Clinical research in patients with female pattern hair loss shows that applying 1 mL of pumpkin seed oil to the scalp daily for 30 days improves hair regrowth similarly to minoxidil 5% foam, 1 mL daily (104974).
• Interstitial cystitis. Although there is interest in using oral pumpkin for interstitial cystitis, there is insufficient reliable information about the clinical effects of pumpkin for this condition.
• Intestinal parasite infection. Although there is interest in using oral pumpkin for intestinal parasite infection, there is insufficient reliable information about the clinical effects of pumpkin for this condition.
• Overactive bladder. Oral pumpkin seed oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in females with overactive bladder shows that taking a specific combination product (Granu Fink femina, Omega Pharma) containing pumpkin seed oil 227 mg, sweet sumac bark extract 56 mg, and hops cone extract 18 mg three times daily for 12 weeks decreases the frequency of urination and leakage and improves quality of life when compared to baseline (103253). The validity of these findings is limited by the lack of a control group. Additionally, it is unclear if these findings are due to pumpkin seed oil, other ingredients, or the combination.
• Urinary tract infections (UTIs). Although there is interest in using oral pumpkin for UTIs, there is insufficient reliable information about the clinical effects of pumpkin for this condition. More evidence is needed to rate pumpkin for these uses.

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LIKELY EFFECTIVE

• Cystic fibrosis. Long-term nebulized hypertonic sodium chloride improves lung function and reduces pulmonary exacerbations in patients with cystic fibrosis. Details: Meta-analyses of clinical research in adults with cystic fibrosis show that, when taken along with a bronchodilator and other standard therapies, nebulized hypertonic sodium chloride in concentrations of 3% to 7%, up to 10 mL twice daily for 4 weeks, increases forced expiratory volume at one second (FEV1) when compared with isotonic saline (sodium chloride 0.9%) (26230,26230). This benefit was not seen at 48 weeks. Other clinical research in adults with cystic fibrosis shows that inhaling sodium chloride 7%, 4 mL twice daily for 48 weeks, does not improve FEV1 when compared with isotonic saline. However, chronic treatment with hypertonic saline does reduce the number of pulmonary exacerbations and increase the number of patients without pulmonary exacerbations when compared with isotonic saline (29402). It is not clear if this benefit occurs in children with cystic fibrosis. The Pulmonary Clinical Practice Guidelines Committee of the Cystic Fibrosis Foundation recommends that individuals with cystic fibrosis aged 6 years or older use nebulized hypertonic saline long-term to improve lung function, reduce the number of exacerbations, and improve quality of life (29403).

POSSIBLY EFFECTIVE

• Amphotericin B nephrotoxicity. Oral sodium chloride seems to prevent nephrotoxicity associated with use of amphotericin B. Details: Clinical research shows that administering oral or intravenous sodium chloride 150 mEq daily during treatment with amphotericin B can attenuate the rise in serum creatinine levels and preserve renal function when compared to treatment with amphotericin B alone (26226).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Bipolar disorder. It is unclear if oral sodium is beneficial in preventing lithium level fluctuations in patients with bipolar disorder. Details: A moderate-sized open-label clinical study in adults with type I bipolar disorder receiving lithium carbonate shows that taking sodium chloride 1 gram daily for 12 weeks along with dietary salt restriction of 1 gram daily reduces the percentage of patients with lithium level fluctuations above 0.8 mEq/L, but does not significantly affect serum sodium, potassium, aldosterone, or creatinine levels when compared with controls who were not salt restricted, but were advised not to consume additional salt at the table (112909). However, the interpretation of these findings is limited by missing data in both groups.
• Canker sores. Although there is interest in using topical sodium chloride for canker sores, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Congestive heart failure. It is unclear if oral sodium is beneficial in patients with acute decompensated heart failure requiring decongestive therapy with diuretics. Details: A moderate-sized clinical study in adults hospitalized with acute decompensated heart failure requiring high-dose intravenous furosemide shows that taking sodium chloride 2 grams three times daily for up to 96 hours does not affect patient weight or serum creatinine levels when compared with placebo (112911). However, the clinical relevance of this study is unclear and it may have been inadequately powered to detect a difference between groups.
• Conjunctivitis. Although there is interest in using ophthalmic sodium chloride for conjunctivitis, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Hyponatremia. Although there is interest in using oral sodium chloride for hyponatremia, there is insufficient reliable information about the clinical effects of oral sodium chloride for this condition.
• Pharyngitis. Although there is interest in using topical sodium chloride for pharyngitis, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Prematurity. It is unclear if oral sodium is beneficial for premature infants. Details: Preliminary clinical research in infants born at less than 32 weeks' gestation shows that adding sodium 4 mEq/kg daily to enteral feedings, starting from the 7th day after birth and continuing through the 35th day, reduces the risk of developing hyponatremia and improves weight gain when compared with adding water (98180). A small, open-label clinical study in newborns less than 35 weeks gestation shows that high sodium intake, defined as an average of 0.25% sodium in maintenance fluids, for 48 hours on day 2 and 3 after birth results in less weight loss within the first 72 hours of life when compared with control, but does not improve mortality, length of hospital stay, or complications from prematurity (112908). However, interpretation of these findings is limited by varied concentrations of sodium as an intervention. More evidence is needed to rate sodium for these uses.

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EFFECTIVE

• Vitamin A deficiency. Oral vitamin A is effective for treatment and prevention of vitamin A deficiency. Details: Clinical and observational research in children shows that taking vitamin A orally is effective for preventing and improving symptoms of vitamin A deficiency, including xerophthalmia, night blindness, and Bitot's spots (82329,82689,82710,90773). Vitamin A deficiency can occur due to abnormal storage and transport of vitamin A in people with abetalipoproteinemia, protein deficiency, diabetes mellitus, hyperthyroidism, fever, liver disease, and cystic fibrosis (7135). However, research suggests that supplementation with vitamin A may not be necessary for most newborns with vitamin A deficiency. An observational study in newborns with vitamin A levels of 0.43-0.59 mcmol/L or >0.59 mcmol/L found that vitamin A levels increased naturally over the first six months of life, regardless of oral vitamin A supplementation. However, in infants with very low vitamin A levels (<0.43 mcmol/L), vitamin A supplementation was associated with significant increases in vitamin A levels at 6 months of age when compared with no supplementation, suggesting that only newborns with very low vitamin A levels should receive oral vitamin A (107298).

POSSIBLY EFFECTIVE

• Aging skin. Topical vitamin A (retinol) formulations seem to improve symptoms of aging skin, such as wrinkles and mottled pigmentation. Details: The vitamin A analog tretinoin (Renova) is a prescription drug approved by the U.S. Food and Drug Administration for adjunctive use in reducing fine wrinkles, hyperpigmentation, and tactile roughness of aging facial skin (103711). However, this drug is not interchangeable with non-prescription, commercially available vitamin A products, which have not been as extensively evaluated in clinical research. Although research evaluating non-prescription topical vitamin A shows benefit for reducing wrinkles, most studies have been small and used different formulations. One small study in adults over 40 years of age shows that applying a pea size amount of 0.075% retinol cream to the face daily for 26 weeks seems to reduce deep and fine wrinkling when compared with placebo. Applying a lower dose of 0.04% retinol cream for 13 weeks seems to reduce fine wrinkling to a lesser degree, with no effect on deep wrinkles, when compared with placebo cream (104458). Another small clinical study in adults over 80 years of age shows that applying 2 mL of retinol 0.4% lotion to the upper arm up to 3 times weekly for 24 weeks reduces visible wrinkles when compared with placebo (94683). Two small studies in females ages 33 to 65 show that applying retinol 0.15%, 0.3% and 0.5% in liquid crystal formulation once daily to the face for 2-3 months improves skin pigmentation, elasticity, and wrinkles when compared with baseline (103680,104464). The validity of these two studies is limited by the lack of a comparator treatment. Topical vitamin A is frequently combined with other ingredients in commercial formulations; however these combinations have rarely been studied. A small clinical study in adults over 35 years with skin aging shows that applying a cream containing retinol 0.5%, niacinamide, resveratrol, and hexylresorcinol seems to improve wrinkling and skin tone when compared with baseline (104455). Another small preliminary clinical trial in adults ages 35-65 years with periorbital lines and wrinkles shows that applying a cream containing retinol modestly improves dryness, puffiness, redness, and darkness when compared with baseline. The retinol was conjugated with lactic acid, and the cream contained other nutrient and herbal ingredients It was applied around the eyes each evening, sometimes used in combination with another product each morning (109747).
• Bronchopulmonary dysplasia. Intramuscular vitamin A may reduce the risk of bronchopulmonary dysplasia (BPD) in very low birth weight infants when given at a dose of 5000 IU three times weekly for 28 days. Lower doses do not seem to be effective. It is unclear if enteral vitamin A is beneficial for BPD. Details: A meta-analysis of 6 clinical trials in premature infants shows that intramuscular administration of vitamin A every other day or three times weekly for 28 days reduces the risk of BPD by around 33% when compared with control (107297). The results from this meta-analysis are primarily driven by a modestly sized clinical trial in very low birth weight infants which shows that intramuscular administration of vitamin A 5000 IU three times weekly for 28 days reduces the risk of BPD by 15% when compared with a sham control (82195). A subgroup analysis of this trial suggests that infants with the lowest BPD risk estimate based on gestational age, birth weight, sex, ethnicity, and oxygen levels 24 hours after birth appear to benefit more from vitamin A therapy than those with higher BPD risk estimates (107296). Previous research in this area utilized a lower dose of only 2000 IU every other day for 28 days, and showed no significant improvement in the rate of BPD (82331,82613). The evaluation of a higher dose was prompted by research noting that the lower doses evaluated in these earlier studies were unable to achieve serum retinol concentrations above 25 mcg/dL, while doses at or above 5000 IU three times weekly could reach this level (82731). Enteral vitamin A has also been investigated. Meta-analyses of two clinical trials show that supplementation with vitamin A at an average of 5,000 IU daily, staring within four days of birth, does not reduce the incidence of BPD when compared with placebo (109750,109753).
• Diarrhea. Vitamin A seems to reduce the incidence of diarrhea in young children. However, it is unclear if oral vitamin A while breastfeeding is beneficial for preventing diarrhea in nursing infants. Details: A meta-analysis of clinical research in children up to age 5 shows that vitamin A supplementation reduces the incidence of diarrhea by 15% and mortality related to diarrhea by 12% when compared with control, usually placebo or no supplementation (109755). However, one small clinical trial in breastfeeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of diarrhea in the nursing infants when compared with placebo (107293).
• Measles. High-dose oral vitamin A seems to reduce mortality from measles in children under 2 years of age and may also reduce the incidence of measles in children up to 5 years of age. Details: Meta-analyses of clinical research show that taking vitamin A does not reduce mortality in children with measles when all ages and/or doses are considered (82373,82502,95055,109755). However, in children with measles who are less than 2 years of age, taking vitamin A 200,000 IU orally for at least two doses seems to reduce mortality by up to 83% when compared with placebo (82373,82502). Also, taking vitamin A seems to reduce the incidence of measles in children ages 6 months to 5 years (95055,109755).
• Night vision. Oral vitamin A as retinyl palmitate seems to reduce night blindness during pregnancy in malnourished patients. Details: Clinical research shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before and during pregnancy reduces pregnancy-related night blindness by 37% in malnourished patients (6154). Some evidence suggests that zinc supplements might potentiate the effects of vitamin A in restoring sight in zinc-deficient pregnant patients affected by night blindness (8630).
• Oral leukoplakia. High-dose oral vitamin A seems to reduce oral leukoplakia lesions in patients that chew tobacco and/or betel nut. Details: Clinical research in patients with tobacco and/or betel nut chewing habits shows that taking oral vitamin A 200,000-300,000 IU weekly for 6-12 months seems to result in remission of leukoplakia lesions in over 50% of participants when compared with placebo (34674,82617). However, it is unknown if vitamin A prevents the development of oral cancer from oral leukoplakia lesions.
• Overall mortality. In children at risk for vitamin A deficiency, oral vitamin A seems to reduce mortality. However, it does not seem to reduce mortality in healthy adults. Details: Despite previous debate on whether the programs supplying high-dose vitamin A in low- and middle-income countries with prevalent vitamin A deficiency are safe and effective for reducing child mortality, most experts, including World Health Organization, recommend high-dose vitamin A supplementation for those children (95055,95724,97170,109755). In 2010, a meta-analysis of 17 trials involving over 194,000 patients, showed that vitamin A supplementation reduces all-cause mortality by about 24% in children 6 months to 5 years of age (82559). However, some research published after this meta-analysis shows conflicting results (90773,90777). In fact, the largest clinical trial conducted to date (Deworming and Enhanced Vitamin A; DEVTA), which was published after the analysis and involved one million preschool children, suggests that high-dose vitamin A supplementation does not reduce mortality (90773). However, this trial was limited due to under-resourcing and undetermined patient consent and treatment compliance (90773). Furthermore, in 2017, a meta-analysis including the DEVTA trial along with 46 additional studies involving over 1.2 million preschool children, shows that vitamin A supplementation does reduce all-cause mortality by 12% when compared with control (95055). This meta-analysis was updated in 2022 with no additional studies or changes in conclusions (109755). Adult mortality is not reduced by vitamin A supplementation. In fact, some evidence even shows that vitamin A supplementation increases mortality when administered to healthy adult patients or those with a stabilized disease (15305,34622,90775).
• Postpartum complications. Oral vitamin A seems to reduce postpartum diarrhea and mortality in malnourished patients. Details: A large clinical study in malnourished pregnant patients in Nepal shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before, during, and after pregnancy reduces the occurrence of blood and mucus in the stool by 93% and the occurrence of diarrhea by up to 90% during the first 6 months postpartum when compared with placebo (2581). Another clinical study in the same population shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before and during pregnancy reduces pregnancy-related mortality by 40% when compared with placebo (6153).
• Retinitis pigmentosa. Oral vitamin A supplementation in children with retinitis pigmentosa seems to slow retinal function decline. Details: Observational and clinical research in children with retinitis pigmentosa shows that taking an age-adjusted dose of vitamin A, up to a maximum dose of 15,000 IU daily, modestly attenuates the decline in retinal function when compared with control (83,97167,103677).
• Ulcerative colitis. Oral vitamin A supplementation in patients with ulcerative colitis seems to improve clinical response and mucosal healing. Details: A clinical study in adults with symptomatic ulcerative colitis despite treatment with 5-aminosalicylic acid shows that taking vitamin A 25,000 IU daily for 2 months reduces disease severity and increases the rate of clinical response and mucosal healing when compared with placebo. The number needed to treat (NNT) for clinical response is 3; the NNT for mucosal healing is 5 (100329).
• Wrinkled skin. Topical vitamin A (retinol) formulations seem to improve photodamage and wrinkles. Details: The vitamin A analog tretinoin (Renova) is a prescription drug approved by the U.S. Food and Drug Administration for adjunctive use in reducing fine wrinkles, hyperpigmentation, and tactile roughness of facial skin (103711). This drug is not interchangeable with non-prescription, commercially available vitamin A products, which have not been as extensively evaluated in clinical research. Still, some research in females ages 35-65 with moderately wrinkled and photoaged skin suggests that commercially available retinol formulations might reduce wrinkles and skin roughness similarly to tretinoin. One study used retinol serum starting at a concentration of 0.25% and increased to 1% over 3 months, compared with tretinoin cream 0.025% gradually increased to 0.1% (103671), while another study compared a gradual release tri-retinol 1.1% cream applied daily for 3 months to tretinoin 0.025% cream (104456). Commercial retinol also seems to be beneficial when compared with placebo. A small study in adults over 40 years old with photodamaged skin shows that applying stabilized retinol 0.1% to the face daily for one year improves wrinkles and mottled pigmentation in over 50% of the participants when compared with a placebo treatment (104463).

POSSIBLY INEFFECTIVE

• Atopic disease. Supplementation with oral vitamin A does not seem to reduce the risk of atopy. Details: Clinical research in infants born in Guinea-Bissau shows that a single dose of vitamin A does not reduce the incidence of atopy when compared with placebo (90779,90780). Furthermore, giving a single dose of vitamin A to some infants, such as low birth weight infants and infants given Bacille Calmette-Guerin (BCG) vaccination, was associated with increased atopy and wheeze (90779).
• Fetal and premature infant mortality. Giving oral vitamin A to malnourished adults during pregnancy and postpartum does not seem to reduce fetal, early infant, or first year mortality. Giving oral or intramuscular vitamin A to the infant also does not seem to reduce mortality in most patients. Details: Most meta-analyses of clinical research in malnourished patients suggest that vitamin A supplementation during pregnancy or postpartum does not reduce fetal, early infant, or first year mortality (6152,34601,34602,34627,82479,82566,82567,90774,90776,90782,90784,95057,109750,109753). Also, giving vitamin A supplements or intramuscular vitamin A to low birth weight infants does not appear to reduce mortality in these patients (82195,82431,82498,90778,90781,95053,107296,107297). Furthermore, vitamin A supplementation in term infants from low or middle income countries also does not appear to reduce the risk of mortality at 6 or 12 months of age when compared with placebo (95054,103674). Some evidence from a meta-analysis of clinical research shows that vitamin A supplementation may reduce the risk of mortality at 6 months in Asian infants, although it appears to increase the risk of mortality at 6 months in studies conducted in Africa. It also appears to increase the risk of mortality in female term infants by 12 months (95054).
• Intestinal parasite infection. Oral high-dose vitamin A does not seem to prevent reinfection with intestinal parasites. Details: Clinical research in children living in Malaysia that were given albendazole 400 mg daily for 3-4 days for parasitic worms, shows that adding a single dose of vitamin A 200,000 IU does not help to prevent reinfection when compared with placebo (90772).
• Melanoma. Oral vitamin A in patients with resected melanoma does not seem to improve survival and disease recurrence. Details: A clinical study in patients with completely resected melanoma shows that taking vitamin A 100,000 IU daily for 18 months does not increase disease-free survival when compared with no supplementation (82670).
• Miscarriage. Oral vitamin A given to the mother does not prevent miscarriage or stillbirth. Details: A meta-analysis of clinical research shows that maternal supplementation with oral vitamin A, either alone or in combination with other vitamins, prior to or during early pregnancy does not reduce the risk of miscarriage or stillbirth when compared with control (104462).
• Sepsis. Most research shows that oral vitamin A does not reduce the risk of sepsis in premature infants. Details: A meta-analysis of three clinical trials in premature infants shows that providing supplemental enteral vitamin A 1500-5000 IU daily, starting within four days of birth, does not reduce the incidence of sepsis when compared with placebo (109753).
• Tuberculosis. Oral vitamin A does not seem to improve tuberculosis disease duration or mortality. Details: Low levels of vitamin A are common in patients with tuberculosis. However, taking vitamin A 2000 IU to 200,000 IU by mouth for 2-24 months does not improve symptoms, decrease disease duration, or reduce mortality when compared with placebo in these patients (82570,103668,109754). This may be due to the fact that vitamin A levels may normalize following the initiation of tuberculosis treatment, even without additional vitamin A supplementation.

LIKELY INEFFECTIVE

• Head and neck cancer. Oral vitamin A taken for 2 years does not seem to improve survival or prevent head and neck cancer recurrence. Details: A large clinical study n patients with a history of head and neck cancer shows that taking vitamin A as retinyl palmitate 300,000 IU daily for 1 year, and followed by 150,000 IU daily for another year, does not reduce the risk of second primary tumors or tumor recurrence when compared with placebo. Also, vitamin A does not seem to improve survival or event-free survival (1710).
• HIV transmission. Oral vitamin A does not reduce vertical HIV transmission risk. There is some concern that vitamin A might increase HIV transmission through breast milk. Details: Observational and intervention research shows that taking vitamin A orally does not decrease the risk of HIV transmission to the fetus during pregnancy, to newborns during delivery, or to infants during early breast-feeding (6376,82470,95059). Preliminary clinical research also shows that vitamin A supplementation of pregnant adults with HIV infection might increase the risk of HIV transmission to their babies through breast milk (9801).
• Lower respiratory tract infections. Oral vitamin A does not reduce the risk for lower respiratory tract infections in children. It is unclear if supplementation of oral vitamin A while breast-feeding reduces the risk of lower respiratory tract infections in nursing infants. Details: Taking vitamin A by mouth does not prevent or reduce symptoms of lower respiratory tract infections, such as cough and fever, in children (82288,82443). Furthermore, some research shows that vitamin A is associated with a slight increase in the risk of respiratory tract infections when administered to children with adequate nutritional status (82288). Additionally, one small clinical trial in breast-feeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of febrile illness or respiratory tract infections in the nursing infants when compared with placebo (107293).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Although prescription vitamin A analogs are approved to treat acne, it is unclear if non-prescription topical vitamin A products help with acne symptoms. Details: The high-dose vitamin A analogs adapalene (Differin) and tazarotene (Tazorac) are prescription drugs approved by the US Food and Drug Administration for the treatment of acne (103712,103713). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol, which have not been extensively evaluated in clinical research. A small preliminary clinical trial in adolescents and young adults with mild to moderate acne shows that applying topical benzoyl peroxide 2.5% each morning and a topical retinol plus salicylic acid product each evening for 12 weeks modestly improves acne severity and other measures of complexion when compared with baseline. All patients also used the same cleanser twice daily (109748). The validity of this finding is limited by the lack of a comparator group.
• Alcohol-related liver disease. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with acute alcoholic hepatitis shows that taking vitamin A in combination with coenzyme Q10 and other vitamins and minerals daily for 6 months does not improve survival when compared with placebo (61392).
• Asthma. It is unclear if oral vitamin A is beneficial for preventing asthma in children. Details: An observational study in children has found that higher dietary intake of vitamin A is associated with a lower risk of asthma. Children in the highest quartile of vitamin A intake (median of 2267 IU daily) at 7 years of age had improved lung function and 32% lower odds of asthma at 11-14 years of age when compared with children in the lowest quartile of vitamin A intake (median of 870 IU daily) (107291).
• Atopic dermatitis (eczema). It is unclear if supplementation of oral vitamin A while breast-feeding is beneficial for preventing eczema in nursing infants. Details: One small clinical trial in breast-feeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of eczema in the nursing infants when compared with placebo (107293).
• Autism spectrum disorder. It is unclear if oral vitamin A is beneficial for improving symptoms of autism. Details: Children with autism spectrum disorder are at increased risk for vitamin A deficiency, and vitamin A levels have been inversely associated with autism symptoms. Preliminary clinical research shows that taking a single dose of vitamin A 200,000 IU slightly improves emotional response, communication, and other symptoms when compared to baseline (97168). The lack of a control group limits the validity of these findings. Another preliminary clinical study in children with autism and vitamin A deficiency shows that taking vitamin A 50,000 IU weekly for 6 months, but not as a single dose of 200,000 IU, seems to improve social impairment scores when compared with control. Controls were children with autism without vitamin A deficiency that did not take a supplement (104459).
• Breast cancer. Although vitamin A intake has been associated with a reduced risk for breast cancer, it is unclear if vitamin A supplements are beneficial. Details: Epidemiological evidence has found an association between high intake of vitamin A and a reduced risk of breast cancer. A meta-analysis of epidemiological research has found that the adults with the highest intake of vitamin A, either from diet alone or also from supplements, reduces the odds of developing breast cancer by 16% when compared with the lowest intake (1444,34610,109752). However, the effects of supplemental vitamin A, specifically, are unclear.
• Cataracts. It is unclear if oral vitamin A is beneficial for cataract prevention. Details: A large-scale population-based study has found that high dietary intake of vitamin A is associated with a reduced risk of nuclear cataracts (6378). Also, other population research has found that the highest dietary intake of vitamin A is associated with a 17% lower risk of cataracts when compared with the lowest intakes (90786). However, there is conflicting evidence regarding the association between blood levels of vitamin A and the risk of cataracts (90786,90944). It is not known if supplemental vitamin A is beneficial.
• Cervical cancer. It is unclear if oral vitamin A is beneficial for cervical cancer prevention. Details: A meta-analysis of clinical research shows that increased vitamin A levels in the blood or higher vitamin A intakes are associated with a reduced risk of cervical cancer. However, this effect is observed when both forms of vitamin A, either retinol or carotenoids, are considered. When only the retinol form is considered, vitamin A supplementation does not seem to reduce the risk of cervical cancer (34613,109752). Also, a meta-analysis of epidemiological research has found that vitamin A intake, either from diet alone or supplements, does not affect the risk of cervical cancer (109752).
• Chemotherapy-induced diarrhea. It is unclear if oral vitamin A helps to prevent diarrhea caused by chemotherapy. Details: A very small clinical study in children receiving chemotherapy shows that taking vitamin A orally does not seem to prevent GI adverse effects, including diarrhea and mouth pain, when compared with control (9802).
• Child development. Oral vitamin A might improve growth and development in children with vitamin A deficiency, but not in those with good nutritional status. Details: Supplementing with vitamin A 60 mg for up to 9 years does not promote or improve child growth in children with appropriate nutritional status (20132). However, in children with vitamin A deficiency, supplementation with vitamin A may improve growth (82246).
• Chronic obstructive pulmonary disease (COPD). There is limited evidence on the oral use of vitamin A in patients with emphysema. Details: Observational research has found that consuming recommended amounts of vitamin A in the diet is associated with 33% lower odds of developing emphysema (103678).
• Colorectal adenoma. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination supplement containing selenium, zinc, vitamin A, vitamin C, and vitamin E orally daily for 5 years or until the recurrence of an adenoma reduces the risk of recurrent large-bowel adenomas by about 40% when compared with placebo in patients with large-bowel adenomas (92903). It is not clear if this benefit is due to vitamin A or other constituents.
• Colorectal cancer. It is unclear if oral vitamin A is beneficial for colorectal cancer prevention. Details: Taking vitamin A alone or in combination with beta-carotene does not seem to reduce the risk of colorectal cancer (12185).
• Coronary artery bypass graft (CABG) surgery. It is unclear if oral vitamin A improves recovery after CABG surgery. Details: Preliminary clinical research shows that taking vitamin A 5000 IU daily (as retinol palmitate) for 21 days starting on the day of CABG surgery reduces time in intensive care after surgery by 46% to 69% compared to a control group not given vitamin A (90783). Supplementation with vitamin A also improves total hospitalization time for those patients with adequate zinc status (90783).
• Coronavirus disease 2019 (COVID-19). It is unclear if oral vitamin A is beneficial for the treatment of mild to moderate COVID-19. Details: Clinical research in COVID-19 outpatients treated with hydroxychloroquine shows that taking vitamin A 25,000 IU daily for 10 days modestly reduces the number of patients with symptoms of fever, body ache, and fatigue when compared with placebo. However, there was no effect on the number of patients with cough, shortness of breath, lack of appetite, chest pain, diarrhea, loss of smell, or headache (109745).
• Depression. It is unclear if oral vitamin A is beneficial for depression. Details: A meta-analysis of observational research has found that dietary intake of vitamin A is inversely associated with depression. The highest intake of vitamin A was associated with a 17% reduced risk of depression when compared with the lowest intake. Also, vitamin A intake was lower in individuals with depression (109743). The effect of vitamin A supplementation is unclear.
• Esophageal cancer. It is unclear if oral vitamin A is beneficial for esophageal cancer prevention. Details: Observational research has found that higher beta-carotene and vitamin A intake is associated with a reduced risk of esophageal cancer (34551,103675). However, evidence from higher-quality clinical research shows that taking vitamin A in combination with beta-carotene does not reduce the risk of esophageal cancer (12185).
• Gastric cancer. It is unclear if oral vitamin A is beneficial for gastric cancer prevention. Details: Taking vitamin A alone and in combination with beta-carotene does not seem to reduce the risk of gastric cancer (12185).
• Glaucoma. It is unclear if oral vitamin A is beneficial for glaucoma prevention. Details: A meta-analysis of observational research has found that a high dietary intake of vitamin A is associated with a 37% reduced risk of glaucoma when compared with a low intake (109742).
• HIV/AIDS. It is unclear if oral vitamin A is beneficial for improving HIV/AIDs outcomes. Details: A meta-analysis of clinical trials and population research shows that maternal vitamin A supplementation of mothers with poor vitamin A status at baseline does not influence child or maternal mortality, hospitalization rate, or HIV/AIDS progression. However, pediatric vitamin A supplementation seems to decrease mortality rates in children with HIV/AIDS when compared with placebo (34529,95059).
• HIV/AIDS-related diarrhea. It is unclear if oral vitamin A is beneficial for preventing diarrhea associated with HIV. Details: A large clinical trial shows that taking vitamin A can decrease the rate of diarrhea-specific mortality by up to 92% in vitamin A-deficient children with or without HIV/AIDS (1465). However, a meta-analysis of clinical research shows that taking vitamin A does not significantly reduce diarrhea-specific mortality when only children with HIV/AIDS are considered (82511). But vitamin A does appear to reduce overall mortality in these children by 50% to 63% (1465,82511).
• Human papillomavirus (HPV). It is unclear if topical or oral vitamin A is beneficial for the resolution of genital warts caused by HPV. Details: A meta-analysis of small clinical trials in patients with genital warts suggests that the oral prescription drugs isotretinoin and etretinate might promote resolution of warts when compared with baseline. However, the topical prescription drug tretinoin 0.05% cream does not seem to help (104460). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol.
• Infant development. It is unclear if intramuscular vitamin A improves the development of low birth weight infants. Details: A meta-analysis of clinical research shows that giving intramuscular vitamin A to very low birth weight infants reduces the risk of chronic lung disease at 36 weeks postmenstrual age by about 13% compared to control (95053). Preliminary clinical research also shows that giving intramuscular vitamin A along with inhaled nitric oxide gas for 3 weeks to low birth weight infants on mechanical ventilation might improve mental development at one year in some of these patients when compared with inhaled nitric oxide gas alone (90778). However, a meta-analysis of clinical research shows that intramuscular vitamin A does not improve neurodevelopment in very low birth weight infants (95053).
• Iron deficiency anemia. It is unclear if oral vitamin A is beneficial for the prevention or treatment of anemia due to iron deficiency. Details: Some research in children and pregnant adults without anemia shows that taking vitamin A increases plasma levels of hemoglobin and ferritin, and may reduce the risk of developing anemia (9518,34627). However, another study in pregnant patients, half of whom had anemia at baseline and half of whom did not have anemia, shows that taking 3000 mcg retinol orally in combination with iron and folate does not improve hemoglobin or erythropoietin concentrations when compared with taking iron and folate (9188). In preterm infants with existing anemia, taking vitamin A 5000 IU and vitamin B complex 40 mg daily improves serum ferritin, hemoglobin, and reticulocyte levels and reduces the need for blood transfusions when compared with taking either vitamin alone. Taking vitamin A alone, however, does not improve these outcomes (100330).
• Leukemia. It is unclear if oral vitamin A is beneficial for leukemia prevention. Details: Preliminary clinical research in adults with chronic myelogenous leukemia shows that taking a specific vitamin A product (Aquasol, Armour Pharmaceuticals) 50,000 IU orally daily in combination with busulfan therapy does not significantly increase progression-free survival or overall survival when compared with busulfan alone. Furthermore, supplementation with vitamin A plus busulfan seems to increase the percentage of patients who experience grade 2 toxicity by about 5-fold when compared with busulfan alone (82652).
• Liver cancer. It is unclear if oral vitamin A is beneficial for liver cancer prevention. Details: Population research has found that vitamin A supplementation or serum levels of vitamin A are not associated with the risk of liver cancer (97169).
• Lung cancer. It is unclear if oral vitamin A is beneficial for lung cancer treatment or prevention. Details: Population research has found that increased dietary intake of vitamin A is not associated with a reduced risk of lung cancer (35628). Furthermore, supplementation with vitamin A and beta-carotene seems to increase the risk of lung cancer in smokers or those exposed to asbestos (2642,34675). A large clinical trial in patients with existing lung cancer shows that vitamin A 300,000 IU daily for one year followed by 150,000 IU daily for a second year does not increase survival (1710). However, some clinical research shows that high-dose vitamin A 300,000 IU daily following curative lung cancer resection reduces the risk of new primary tumors in patients heavily exposed to tobacco (7875).
• Malaria. It is unclear if oral vitamin A is beneficial for reducing symptoms of malaria in young children. Details: Taking vitamin A orally seems to help decrease symptoms of malaria in children less than 3 years of age living in endemic areas (1464). However, other clinical research shows that single doses of vitamin A 100,000 to 200,000 IU do not improve coma resolution, convulsions, fever, parasite clearance, or mortality in infants and children less than 5 years of age with cerebral malaria (90785).
• Multiple sclerosis-related fatigue. It is unclear if oral vitamin A is beneficial for reducing fatigue in patients with multiple sclerosis. Details: Preliminary clinical research in patients with relapsing-remitting multiple sclerosis receiving interferon beta-1a shows that taking vitamin A 25,000 IU (as retinyl palmitate) (Zahravi Pharmaceutical) daily for 6 months followed by 10,000 IU daily for 6 months, improves physical, cognitive, and psychosocial fatigue when compared with placebo (95052).
• Necrotizing enterocolitis (NEC). A meta-analysis of several small clinical trials suggests that intramuscular vitamin A does not seem to prevent NEC. Details: A meta-analysis of 3 small clinical studies in very low birth weight infants shows that intramuscular administration of vitamin A 1500-5000 IU every other day or three times weekly for 28 days does not reduce the risk of NEC when compared with a control (107297).
• Non-Hodgkin lymphoma. It is unclear if oral vitamin A is beneficial for non-Hodgkin lymphoma prevention. Details: Population research has found that intake of vitamin A at levels above 2330 mcg daily is associated with a 17% lower risk of non-Hodgkin lymphoma when compared with those whose daily intake of vitamin A is less than 642 mcg per day (90945).
• Nonmelanoma skin cancer. It is unclear if oral vitamin A is beneficial for nonmelanoma skin cancer prevention. Details: Observational research over 26 years found that higher dietary vitamin A intake is associated with a 12% reduced risk for cutaneous squamous cell carcinoma in healthy patients when compared with lower vitamin A intake (101673).
• Oral clefts. It is unclear if oral vitamin A is beneficial for oral cleft prevention. Details: A meta-analysis of observational research has found that periconceptional use of vitamin A, from diet and/or supplements, is associated with a 13% reduced incidence of cleft lip alone or with a cleft palate, but is not associated with the risk of cleft palate alone, in the child (109751).
• Osteoarthritis. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with osteoarthritis shows that taking a specific product containing vitamin A in combination with selenium, vitamin C, and vitamin E (Selenium ACE, Carls-Berghs Farmaceutiska AB) does not appear to alleviate symptoms when compared with placebo (74449).
• Ovarian cancer. It is unclear if oral vitamin A is beneficial for ovarian cancer prevention. Details: Most observational research has found that increased dietary intake of vitamin A is associated with a reduced risk of developing ovarian cancer (9193,103679,109752). The most recent meta-analysis of epidemiological research has found that adults with the highest intake of vitamin A, either from diet alone or supplements, reduces the odds of developing ovarian cancer by 19% when compared with the lowest intake (109752).
• Pancreatic cancer. It is unclear if oral vitamin A is beneficial for pancreatic cancer prevention. Details: A meta-analysis of observational research has found that higher intake of vitamin A is associated with a reduced risk of pancreatic cancer; however, this benefit appears to be limited to only hospital-based cases and studies conducted in Europe (95060). In contrast, a meta-analysis of clinical research shows that taking vitamin A in combination with beta-carotene does not reduce the risk of pancreatic cancer (12185).
• Parkinson disease. It is unclear if oral vitamin A prevents Parkinson disease development. Details: Population research has found that blood levels or dietary intake of vitamin A are not associated with the risk of Parkinson disease (91164).
• Photoreactive keratectomy. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking a specific product (Evitex capsules, Alcon) containing vitamin A along with vitamin E seems to improve healing after photoreactive keratectomy. High dose (50,000 to 75,000 IU) vitamin A in the form of retinol palmitate taken daily with vitamin E (alpha-tocopheryl nicotinate) 460-590 mg daily seems to accelerate re-epithelialization, reduce haze formation, and improve visual acuity in patients undergoing laser surgery for myopia (348).
• Pneumonia. Oral vitamin A does not seem to prevent mortality related to pneumonia in children. However, it is unclear if vitamin A reduces symptom severity and hospitalization in children. Details: Clinical research in children living in developing countries shows that taking vitamin A orally does not prevent mortality related to pneumonia (1466,82362,82504,82717,109749). However, the evidence related to symptom duration and severity is mixed. A large study and early meta-analyses show that vitamin A does not prevent pneumonia or decrease the severity or length of hospitalization in children with pneumonia (1466,82362,82504,82717). A more recent meta-analysis also shows that giving vitamin A to children at or below 5 years of age does not affect the duration of hospitalization (109755). The best evidence to date comes from a recent meta-analysis of randomized clinical trials. This meta-analysis shows that, when given in combination with conventional therapy to children up to 10 years of age, vitamin A reduces the duration of symptoms including fever, cough, lung rale, and shortness of breath, as well as the duration of hospitalization and time to a negative X-ray, when compared with conventional therapy alone (109749). However, the number of trials evaluating each endpoint is small and more research is needed to confirm these findings.
• Prematurity. It is unclear if vitamin A reduces the duration of hospitalization for premature infants. Details: A meta-analysis of four randomized controlled trials in preterm infants shows that providing supplemental enteral vitamin A 1500-5000 IU daily, starting within four days of birth, does not reduce the duration of hospitalization when compared with placebo (109750).
• Prostate cancer. It is unclear if oral vitamin A is beneficial for prostate cancer prevention. Details: Observational studies suggest that dietary intake of vitamin A is not associated with a reduced risk of prostate cancer (14134).
• Psoriasis. It is unclear if topical vitamin A is beneficial for psoriasis symptoms. Details: The vitamin A analog tazarotene (Tazorac) is a prescription drug that is approved by the U.S. Food and Drug Administration to treat stable plaque psoriasis covering up to 20% body surface area (103713). This drug is not interchangeable with non-prescription, commercially available vitamin A products, such as retinol.
• Radiation proctopathy. It is unclear if oral vitamin A is beneficial for reducing chronic radiation proctopathy symptoms. Details: A small clinical study in patients experiencing chronic radiation proctopathy caused by pelvic radiotherapy shows that taking retinol palmitate 10,000 IU daily for 90 days might reduce rectal symptoms when compared with placebo (82350).
• Retinopathy of prematurity. Most small studies show that oral or intramuscular vitamin A does not reduce the risk of retinopathy of prematurity (ROP). Details: A meta-analysis of 4 small clinical studies in very low birth weight infants shows that intramuscular administration of vitamin A 2000-10,000 IU every other day or three times weekly, or oral vitamin A 2000 IU daily, for 28 days does not reduce the risk of ROP when compared with a control (107297). Another meta-analysis of clinical research shows that providing supplemental enteral vitamin A 1500 IU or an average of 5000 IU daily, starting within four days of birth, does not reduce the incidence of severe ROP (109750,109753). However, a very small clinical study in preterm infants, which was not included in the meta-analysis, shows that receiving retinol palmitate drops 3000 IU/kg daily for 28 days reduces the risk of ROP by 88% when compared with no treatment (103672).
• Urinary tract infections (UTIs). It is unclear if adding oral vitamin A to antibiotic therapy is beneficial for symptoms of acute pyelonephritis in young females. Details: A small clinical study in females 2-12 years of age with a first occurrence of acute pyelonephritis shows that taking vitamin A 1500 units/kg daily for 10 days in conjunction with antibiotics decreases the duration of fever by about 1.3 days and reduces urinary frequency by about 1.5 episodes per day when compared to taking placebo with antibiotics. Taking vitamin A might also reduce the occurrence of moderate or severe renal scarring after 6 months when compared with placebo (100327). The validity of these findings is limited by small study size and a high dropout rate.
• Warts. It is unclear if topical or oral vitamin A improves the resolution of viral warts. Details: A meta-analysis of observational and clinical research in patients with viral warts suggests that receiving prescription oral retinoids (isotretinoin, acitretin, etretinate) seems to produce a 61% rate of wart resolution. Prescription topical retinoids seems to produce a 64% rate of wart resolution (104461). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol. More evidence is needed to rate vitamin A for these uses.

(Read more about VITAMIN A)

EFFECTIVE

• Vitamin C deficiency. Oral or intramuscular vitamin C is effective for preventing or treating vitamin C deficiency. Details: Administering vitamin C orally or intramuscularly prevents and treats vitamin C deficiency, including scurvy. Vitamin C administration can reverse complications of scurvy within 2 days to 3 weeks (4844). In newborns with transient tyrosinemia due to vitamin C deficiency, oral or intramuscular vitamin C can correct this condition (15).

POSSIBLY EFFECTIVE

• Anemia of chronic disease. Oral vitamin C seems to improve markers of anemia in patients on hemodialysis. Details: Meta-analyses of clinical research in hemodialysis patients with anemia shows that treatment with vitamin C 200-300 mg three times weekly for 3-6 months increases hemoglobin levels by approximately 0.9 grams/dL, increases transferrin saturation by about 8%, and decreases the required recombinant human erythropoietin dose by 17 U/kg weekly when compared with standard care (83447,83475).
• Atrial fibrillation. Oral and intravenous vitamin C seems to help prevent atrial fibrillation after cardiac surgeries. Details: Meta-analyses of clinical research show that taking vitamin C prior to and after cardiac surgery reduces the risk of postoperative atrial fibrillation by 27% to 53%. Most studies administered vitamin C at doses of 1-2 grams orally daily for 1-3 days prior to cardiac surgery, followed by 1-2 grams in two divided doses daily for 4-5 days after cardiac surgery. Some studies provided vitamin C intravenously at similar doses, but oral vitamin C seems to be more effective (91233,96703,96705). Despite these findings, a meta-analysis of clinical research conducted only in the U.S. does not support the benefit of vitamin C for reducing postoperative atrial fibrillation (96703). These differences may be related to lifestyle factors such as nutrition, as well as differences in hospital treatments. Vitamin C has also been studied in combination with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with evidence of benefit (90701).
• Bowel preparation. Powdered vitamin C is approved for use as part of a polyethylene glycol-based bowel preparation for colonoscopy. Details: Clinical research shows that treatment with 2 liters of oral solution containing polyethylene glycol (PEG) plus vitamin C achieves a similar quality of bowel cleansing as treatment with 4 liters of PEG when administered on the evening prior to colonoscopy or when administered in a split-dose regimen. Patients given 2 liters of PEG plus vitamin C solution also have better adherence and experience fewer adverse events, such as nausea, vomiting, or abdominal bloating, compared to patients treated with 4 liters of PEG solution without vitamin C (90413,90415,90420,90424,90428). This treatment also appears to be effective and tolerable in elderly patients aged 60-79 years, including those with poor bowel habits and a high number of comorbidities (108085). Other clinical research in older adults undergoing bowel preparation for colonoscopy also shows that taking 1 liter of PEG plus vitamin C (CleanViewAL, Taejoon Pharm) results in similar quality of bowel cleansing overall and per segment with similar tolerability and adverse effects as sodium picosulfate 170 mL plus magnesium citrate or oral sulfate solution alone (111297,112476). The most common PEG plus vitamin C preparation used in clinical research is MoviPrep (Norgine BV), which contains macrogol 3350 100 grams, sodium sulfate 7.5 grams, sodium chloride 2.7 grams, potassium chloride 1 gram, vitamin C 4.7 grams, and sodium ascorbate 5.9 grams per liter of solution (90413,90415,90424). In the U.S., MoviPrep is approved by the Food and Drug Administration (FDA) for bowel preparation prior to a colonoscopy.
• Common cold. Oral high-dose vitamin C might modestly reduce cold symptoms; however, taking vitamin C prophylactically does not seem to prevent the development of a cold. Details: There is substantial controversy about the effectiveness of vitamin C for treating the common cold (1969,1989,7100,9835,9836). The majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patients (1966,1967,1968,1987,6458,7102,9832,83487). However, other studies have found no effect with doses up to 3 grams daily (9833). A meta-analysis of clinical research suggests that vitamin C supplementation decreases the incidence of cold in individuals exposed to physical stress, but not in the general population (83487). Other research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. Also, there may be a dose-dependent response; doses of at least 2 grams daily seem to work better than 1 gram doses (9834). Taking vitamin C supplements prophylactically does not decrease the risk of catching a cold (1966,1967,1968,1987,3042,6458,7101,9832). Dietary intake of vitamin C also does not seem to affect the risk of getting a cold (10780).
• Complex regional pain syndrome. Most research shows that taking oral vitamin C after a wrist or distal radius fracture or after orthopedic surgery seems to reduce the risk of developing complex regional pain. Details: Although some research has found no benefit in patients with distal radius (i.e. wrist) fractures (90411,96702), most clinical research shows that taking vitamin C 500 mg daily, and possibly doses of up to 1500 mg daily, for 45-50 days beginning immediately after fracture can reduce the risk of developing complex regional pain syndrome (2045,16302,96700,96706). Reasons for discrepancies are unclear but might relate to differences in diagnostic criteria for complex regional pain syndrome (96702). Research in patients undergoing orthopedic surgery has also shown benefit with the use of vitamin C for the prevention of complex regional pain syndrome (90422,108076,108087). One meta-analysis of clinical research in patients undergoing wrist, foot, or ankle surgery shows that taking vitamin C 500-1000 mg for 42-50 days following surgery reduces the rate of complex regional pain syndrome, and may improve pain following ankle or foot surgery, when compared with placebo (108076). The validity of these findings is limited by the high heterogeneity of included trials. Another meta-analysis of clinical research in patients undergoing orthopedic surgery (i.e. wrist, knee, ankle, foot, lumbar, rotator cuff) suggests that oral and intravenous vitamin C may have similar effectiveness; however, this evidence is low quality (108087).
• Exercise-induced respiratory infections. High-dose oral vitamin C seems to reduce the risk of respiratory infections associated with strenuous exercise. Details: Some preliminary clinical research suggests that prophylactic use of vitamin C in doses of 600 mg to 1 gram daily for 3-8 weeks before heavy physical exercise, such as a marathon, might prevent upper respiratory infections that sometimes follow heavy exercise (9831,83370). More recently, high doses of vitamin C have been studied. A large clinical study in army recruits undergoing basic military training shows that taking vitamin C 6 grams daily for one month reduces the odds of getting a cold by 20% when compared with placebo (102975).
• Hypercholesterolemia. Oral vitamin C seems to reduce lipid levels in patients with hypercholesterolemia. Details: A meta-analysis of clinical research in patients with hypercholesterolemia shows that taking vitamin C 500 mg daily for at least 4 weeks reduces low-density lipoprotein (LDL) cholesterol by about 8 mg/dL and reduces triglycerides by about 20 mg/dL when compared with control (83445).
• Hypertension. Oral vitamin C seems to modestly reduce blood pressure in patients with hypertension. Details: Vitamin C seems to modestly reduce systolic blood pressure, without meaningful effects on diastolic blood pressure (2044,9822,13162,83483,102974). A meta-analysis of 13 clinical trials in patients with hypertension, with or without other comorbidities, shows that taking a median dose of vitamin C 500 mg daily for 8 weeks reduces systolic, but not diastolic, blood pressure by about 5 mmHg. Some of the studies used vitamin C in combination with other supplements, such as vitamin E and magnesium. When studies assessing vitamin C alone were analyzed, the magnitude of reduction in systolic blood pressure decreased (83483). A newer meta-analysis of small clinical studies in patients with essential hypertension shows that taking vitamin C 200 mg or more daily reduces systolic blood pressure by about 4 mmHg and diastolic blood pressure by about 2 mmHg (102974). However, this newer analysis omitted numerous relevant studies and included studies with normotensive patients and those without an adequate control, limiting the validity of its findings.
• Laser skin resurfacing. Topical vitamin C seems to reduce erythema occurring after cosmetic laser skin resurfacing procedures intended to reduce scars and wrinkles. Details: There is some evidence that an aqueous formulation of topical vitamin C can decrease the degree and duration of erythema following cutaneous carbon dioxide laser resurfacing for scar and wrinkle removal (1959).
• Lead toxicity. Dietary vitamin C seems to lower concentrations of lead in the blood. Details: Observational research has found that consuming more vitamin C from dietary sources is associated with lower blood concentrations of lead. People who consumed at least 340 mg of vitamin C daily as part of the diet had lower blood lead levels than those who consumed less than 100 mg vitamin C daily (3097,3098,3099).
• Nitrate tolerance. Oral vitamin C might prevent nitrate tolerance in some patients. Details: Small clinical studies show that taking vitamin C orally seems to prevent the development of nitrate tolerance in patients taking sublingual nitroglycerin. There is some evidence that short-term vitamin C supplementation can prevent tolerance to the vasodilatory effects of nitrates (1441,1961).
• Postoperative pain. Oral or intravenous vitamin C might prevent acute postoperative pain following certain surgeries. It is unclear if vitamin C reduces chronic postoperative pain. Details: A meta-analysis of 7 small clinical studies in adults undergoing elective surgery shows that receiving perioperative vitamin C, either as 1 gram orally, 2-3 grams intravenously, or 50 mg/kg intravenously, modestly reduces acute pain and opioid requirements for up to 24 hours when compared with control (105457). Most surgeries were laparoscopic and included cholecystectomy, colectomy, hysterectomy; two non-laparoscopic surgeries included uvulopalatopharyngoplasty with tonsillectomy and major abdominal surgery (90418,99840,105457). A meta-analysis of clinical trials in adults undergoing noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, kidney transplantation) shows that administering perioperative vitamin C, either orally or intravenously, reduces postoperative intravenous morphine requirements at 2, 24, and 48 hours after surgery and improves pain scores at 2, 6, and 24 hours after surgery when compared with placebo. The dose of vitamin C did not appear to impact outcomes. However, when only laparoscopic surgeries are included, perioperative vitamin C does not improve pain or morphine use when compared with placebo (108087). A moderate-sized clinical study in adults undergoing transurethral resection of a bladder tumor under general anesthesia shows that administering intravenous vitamin C 1 gram after induction of anesthesia reduces the incidence and severity of catheter-related bladder discomfort immediately after surgery and at 1 and 2 hours postoperatively, but not 6 hours, when compared with placebo. However, vitamin C does not reduce postoperative pain scores or analgesic requirements when compared with placebo (111645). Further research is needed to determine the effects of vitamin C for acute postoperative pain. Vitamin C has also been evaluated for reducing chronic pain after surgery. Clinical research in patients undergoing surgery for foot or ankle trauma shows that taking vitamin C 500 mg orally twice daily postoperatively for 6 weeks reduces pain scores when compared with placebo at 2 weeks and 6 weeks. The mean total amount of diclofenac used for pain relief over the 6-week period is also reduced, from 5.7 grams with placebo to 3.4 grams with vitamin C (102131).
• Wrinkled skin. Topical vitamin C might reduce the appearance of existing wrinkles. Details: Topical preparations containing vitamin C seem to improve the appearance of wrinkled skin. Some evidence shows that vitamin C 3% applied for 12 weeks might reduce facial wrinkles (14008). A small clinical study shows that applying a dissolving microneedle patch containing vitamin C 5.6% every 4 days for 12 weeks to crow's feet on one side of the face reduces wrinkles when compared to control treatment applied on the other side of the face (98780). Other clinical research in females aged 30-60 years shows that applying an oil-soluble cream containing the vitamin C derivative tetra-isopalmitoyl ascorbic acid 1%, 2%, or 3% to the periorbital area twice daily for 8 weeks reduces visual wrinkle grading when compared with placebo. A dose analysis shows greater improvements in wrinkle parameters, average wrinkle depth, and mean depth with the lower concentration, while greater improvements in maximum roughness and maximum depth are observed with the higher concentration (108072). This study only included individuals defined as having Fitzpatrick skin type III or IV; it effects on other skin types is unclear. Preparations containing vitamin C in combination with other ingredients have also been investigated. A small low-quality trial in females with moderately photodamaged and hyperpigmented facial skin shows that applying a moisturizer with vitamin C 30%, vitamin E, and coenzyme Q10 once daily in the morning, along with applying retinol 0.5% once daily or once every other day for 12 weeks, seems to improve skin tone, photodamage, and wrinkles when compared to baseline (99085). In another small trial, a topical preparation containing vitamin C 10% as L-ascorbic acid along with acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months improves fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the beneficial effects of these products are due to vitamin C, other ingredients, or the combination.

POSSIBLY INEFFECTIVE

• Acute bronchitis. Oral vitamin C doesn't seem to improve symptoms of acute bronchitis. Details: A clinical study in adults with acute bronchitis shows that taking vitamin C orally 500 mg on day 1, then 250 mg on days 2 through 5 (similar to an azithromycin regimen) doesn't seem to have any effect on quality of life or bronchitis duration when compared with azithromycin (9827).
• Asthma. Oral vitamin C doesn't seem to prevent asthma or improve lung function. Details: Although some observational research has found that some patients with asthma might have lower serum vitamin C levels (5873), other observational research found that increased dietary vitamin C intake is not associated with a reduced risk of asthma or improved lung function (15006,34567). In addition, clinical research shows that supplemental intake of vitamin C does not reduce asthma symptoms, improve lung function, or reduce the use of inhaled steroids in asthma patients (90409).
• Atherosclerosis. Oral vitamin C does not seem to reduce the progression of atherosclerosis. Details: A clinical study shows that taking a specific combination product containing slow-release vitamin C 250 mg and vitamin E 136 IU (CellaVie, Ferrosan A/S) twice daily modestly slows the 3-year progression of atherosclerosis of the carotid artery in males, but not females. This result persisted at a 6-year follow-up of this study (1918,10473). However, when this form of vitamin C is used alone, it does not slow the 3-year progression of atherosclerosis of the carotid artery (1918).
• Bladder cancer. Oral vitamin C does not reduce the risk of bladder cancer or mortality from bladder cancer. Details: Epidemiological research has found that supplemental vitamin C intake is not associated with mortality rate in patients with bladder cancer (9839). A secondary analysis of a large clinical trial, the Physicians' Health Study II, in healthy men aged at least 50 years also shows that taking vitamin C 500 mg daily alone or with vitamin E 400 IU daily for up to 10 years does not reduce the risk of developing bladder cancer or bladder cancer-related deaths when compared with placebo (90097).
• Cardiovascular disease (CVD). Oral vitamin C does not seem to be beneficial for either primary or secondary CVD prevention. Details: Vitamin C does not seem to be beneficial for primary prevention of CVD. Some population research has found that higher supplemental vitamin C or dietary vitamin C has been associated with a reduced risk of developing CVD (10358,14108,109779), while other observational research has found no benefit (34566,10358,14108). However, meta-analyses of clinical research in healthy patients show that vitamin C supplementation does not prevent CVD or coronary heart disease when compared with control (97308,104025). In 2004, the American Heart Association stated that current evidence does not justify use of antioxidants such as vitamin C for reducing the risk of CVD (12142). Evidence is also negative for secondary prevention in people with coronary heart disease. Population studies have found that higher serum vitamin C was associated with no effect or decreased CVD mortality from CVD (3910,5878). A meta-analysis of two large clinical trials shows that vitamin C supplementation does not reduce CVD events or CVD mortality when compared with control (97308).
• Colorectal cancer. Oral vitamin C does not seem to prevent colorectal cancer. Details: Population research has found that dietary vitamin C intake is not associated with a reduced risk of developing colon cancer. When total vitamin C intake from food and supplements is considered, there is a modest association (34600). However, most clinical trials show that supplemental vitamin C, alone or along with other antioxidants, does not reduce the risk of colorectal cancer development, colorectal cancer or adenoma recurrence, or colorectal cancer-related mortality (34580,34581,34594,90097,90089,92903).
• Coronavirus disease 2019 (COVID-19). Oral vitamin C, even at high doses, does not seem to speed recovery from COVID-19 in non-hospitalized patients. An analysis of clinical research suggests that oral or intravenous vitamin C might reduce mortality in patients hospitalized with COVID-19; however, given that nearly all individual studies are small and do not show benefit, larger and higher-quality studies are needed to confirm these findings. Details: A clinical study in adult outpatients with confirmed COVID-19 shows that taking oral vitamin C (ascorbic acid) 8000 mg in 2-3 divided doses daily, alone or with zinc gluconate 50 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). The study was terminated prior to complete enrollment due to futility and apparent lack of effect from vitamin C and/or zinc supplementation. Limitations of this study include a lack of placebo control and blinding. Additionally, this study has been criticized for methodologic concerns (106624). Another small clinical trial in adult outpatients with confirmed COVID-19 shows that taking vitamin C 1000 mg daily for 14 days does not improve symptoms or quality of life when compared with placebo (109462). Vitamin C has also been evaluated in patients hospitalized with COVID-19. Individual prospective and retrospective studies in critically ill patients hospitalized with COVID-19 in various countries have found that administering vitamin C, either enterally as 500-1000 mg daily or intravenously as 8-24 grams daily or 50 mg/kg daily, does not significantly reduce in-hospital or short-term mortality, hospital length of stay, or end-organ failure when compared with control groups receiving standard care alone. Additionally, all but one study found no change in the need for mechanical ventilation (105458,105465,106937,106938,108075,108079,108081). One small study found a small improvement in survival rate when compared with standard care; however, the overall survival rate in this study was low (108075). Additionally, one clinical study in patients hospitalized in Turkey with COVID-19 shows that adding high-dose intravenous sodium ascorbate 50 mg/kg to a treatment regimen of hydroxychloroquine, azithromycin, and zinc may improve recovery time, with 57% and 39% of patients achieving total recovery at day 15 in the vitamin C and control groups, respectively (108071). However, the validity of this trial is limited due to unclear reporting. Additionally, these small studies were likely underpowered to detect differences between the vitamin C and control groups. A meta-analysis of 10 clinical trials and 9 observational studies in patients hospitalized with COVID-19 shows that receiving oral or intravenous vitamin C daily reduces the odds of in-hospital mortality by 41% when compared with control. When only clinical trials were considered, the odds of in-hospital mortality were decreased by 56%; however, this reduction was only identified in studies using vitamin C 10 grams daily or less. Conversely, supplementation with vitamin C increased the length of intensive care unit (ICU) stay by nearly 2 days and did not impact length of hospital stay or reduce the need for mechanical ventilation, liver injury, or cardiac injury (109955). Given that most individual studies in this analysis did not show improvements in mortality with vitamin C, larger and higher-quality prospective studies are needed to determine the role of vitamin C in hospitalized patients with COVID-19. Vitamin C has also been evaluated in patients with long COVID. Preliminary clinical research in adults with long COVID and persistent fatigue shows that taking a specific combination product containing vitamin C 500 mg and L-arginine 1.66 grams (Bioarginina C, Farmacetici Damor) for 28 days increases 6-minute walk test distance by 10% and reduces self-reported fatigue when compared with placebo (110390).
• Fetal and premature infant mortality. Oral vitamin C does not seem to prevent neonatal death. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of neonatal death (83472,96707).
• Fractures. Oral vitamin C does not seem to improve fracture healing. Details: Clinical research shows that taking vitamin C 500 mg daily for 50 days following an acute distal radial fracture does not improve physical function, symptoms, or healing rates when compared with placebo (90411).
• Helicobacter pylori. Oral vitamin C does not seem to improve eradication of H. pylori. Details: Most clinical research shows that treatment with vitamin C, alone or in combination with vitamin E, does not improve the eradication rate of H. pylori when taken with a standard eradication regimen when compared with the eradication regimen alone (83476,90094).
• Hereditary motor and sensory neuropathy. Oral vitamin C does not seem to improve neuropathy in these patients. Details: In a meta-analysis of five studies in patients with Charcot-Marie-Tooth disease type 1A, taking vitamin C 1-4 grams orally daily for 1 year did not improve neuropathy when compared with placebo (99084). Continuing vitamin C 4 grams daily for 2 years also does not improve neuropathy in these patients (90419).
• Interferon-related retinopathy. Oral vitamin C does not seem to improve retinopathy associated with interferon therapy. Details: A small clinical study in patients with chronic hepatitis C receiving interferon therapy shows that taking vitamin C 600 daily orally does not seem to reduce the risk of retinopathy from interferon therapy when compared with control (10355).
• Leukemia. Oral vitamin C does not seem to reduce the risk of leukemia or mortality from leukemia. Details: A large clinical trial in men aged at least 50 years shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing leukemia or leukemia-related deaths when compared with placebo (90097).
• Low birth weight. Oral vitamin C does not seem to reduce the risk of infants being born with a low birth weight. Details: Meta-analyses of clinical research show that maternal use of oral vitamin C alone or with other supplements does not reduce the risk of giving birth to infants with low birth weight when compared with control (83450,83472).
• Lung cancer. Oral vitamin C does not seem to reduce the risk of lung cancer. Details: Two meta-analyses of clinical research suggest that taking vitamin C, alone or in combination with vitamin E, does not reduce the incidence of lung cancer or lung cancer-related mortality (34528,34632). Also, a clinical study in females shows that taking supplemental vitamin C 500 mg daily, with or without vitamin E and beta carotene, is associated with an INCREASED risk of lung cancer when compared with placebo (34580).
• Melanoma. Oral vitamin C does not seem to reduce the risk of melanoma. Details: Clinical research shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing melanoma or melanoma-related deaths when compared with placebo in men aged at least 50 years (90097).
• Miscarriage. Oral vitamin C does not seem to reduce the risk of miscarriage. Details: A meta-analysis of clinical research shows that taking vitamin C alone or with other supplements does not reduce the risk of miscarriage when compared with control (94820).
• Overall mortality. Oral vitamin C does not reduce overall mortality. Details: Although population research suggests that higher dietary intake and higher plasma vitamin C levels are associated with a reduced risk of mortality from all causes (3910,109779), vitamin C supplementation does not seem to affect overall mortality. Meta-analyses of clinical research show that taking vitamin C supplements does not reduce overall mortality when compared with control (34622,111641). Clinical studies of vitamin C used in combination with vitamin E, beta carotene, and/or selenium and zinc, also show no benefit for overall mortality (9817,14109).
• Pancreatic cancer. Oral vitamin C does not seem to prevent pancreatic cancer. Details: Observational research has found that increased dietary vitamin C intake is associated with up to a 30% reduced risk of pancreatic cancer (99083,99086). However, clinical research shows that supplemental vitamin C 500 mg daily does not reduce the risk of pancreatic cancer in females (34580). Also, taking vitamin C in combination with beta-carotene plus vitamin E does not reduce the risk of pancreatic cancer (12185,34581).
• Pre-eclampsia. Oral vitamin C does not seem to prevent pre-eclampsia. Details: Despite some early positive research in high-risk pregnancies, the majority of meta-analyses and clinical studies show that taking vitamin C alone or with vitamin E or other supplements does not reduce the risk of pre-eclampsia when compared with control. There is even some concern that vitamin C supplementation may increase the risk of gestational hypertension (3236,83450,83472,83474,96707).
• Preterm labor. Oral vitamin C does not seem to prevent preterm labor. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of preterm labor when compared with control (83450,83472,96707).
• Prostate cancer. Oral vitamin C does not seem to prevent prostate cancer. Details: A large-scale clinical study (The SU.VI.MAX study) shows that a combination of vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, selenium 100 mcg, and zinc 20 mg, taken daily for an average of 8 years, does not reduce the risk of prostate cancer overall. However, it might reduce the risk of prostate cancer in those who have normal PSA levels. It does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). Another large scale study (Physician's Health Study II) shows that taking vitamin C 500 mg daily for an average of 8 years does not significantly reduce the risk of prostate cancer when compared with placebo (16708). Similarly, results from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial seem to show that supplemental or dietary intake of vitamin C does not reduce the risk of prostate cancer when compared to individuals not taking vitamin C (14124).
• Radiation dermatitis. Topical vitamin C does not seem to prevent radiation dermatitis in cancer patients. Details: A small clinical study shows that applying a 10% vitamin C solution does not appear to protect from radiation dermatitis when applied to the scalps of patients treated with radiation for intracranial tumors (789).
• Small for gestational age (SGA). Oral vitamin C does not seem to reduce SGA. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of small for gestational age birth when compared with control (83450,83472).
• Stillbirth. Oral vitamin C does not seem to prevent stillbirth. Details: Meta-analyses of clinical research show that maternal use of vitamin C alone or with other supplements does not reduce the risk of stillbirth when compared with control (83472,96707).

LIKELY INEFFECTIVE

• Sepsis. Intravenous vitamin C, alone or in combination with thiamine and/or hydrocortisone, does not prevent organ failure, reduce intensive care or hospital length of stay, or reduce mortality in sepsis or septic shock. Details: Observational research suggests that patients with septic shock are more likely to have low plasma levels of vitamin C (100317). However, two randomized clinical trials in patients with sepsis show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027). A clinical study in patients with septic shock shows that administering an intravenous bolus of vitamin C 1000 mg followed by a continuous infusion of 250 mg/hour for 96 hours, starting within 24 hours of vasopressor initiation, does not improve 28-day or intensive care unit (ICU) mortality when compared with placebo. A subgroup analysis shows that the addition of corticosteroids does not affect outcomes in either group (108078). This study may have been inadequately powered to detect a difference between groups. Also, a larger clinical trial in adults with sepsis receiving vasopressor therapy in the ICU shows that intravenous administration of vitamin C 50 mg/kg every 6 hours for up to 4 days increases the risk of death or persistent organ dysfunction at day 28 by 14% to 21% when compared with placebo. There were no differences in mortality at 6 months (109459,111643). Vitamin C has also been frequently studied in patients with sepsis and septic shock in a specific combination regimen (HAT therapy) which includes intravenous vitamin C 1.5-2 grams with hydrocortisone 50 mg every 6 hours and thiamine 200 mg every 12 hours. While some retrospective research has found HAT therapy to be beneficial in sepsis (100315,102980), high quality, prospective clinical research has not confirmed these findings (105447,106620,109956). Several meta-analyses of randomized controlled trials and small clinical studies in patients with sepsis or septic shock show that intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, does not reduce short- or long-term mortality, ICU or hospital length of stay, kidney injury, or duration of mechanical ventilation, but modestly improves duration of vasopressor use and procalcitonin clearance, when compared with placebo or standard care. These analyses also show mixed results with respect to improvement in sequential organ failure assessment (SOFA) scores within 72 hours (105447,106620,106935,108073,109460,111298,111300,111301,111642,112479). Most studies included in the analyses administered HAT therapy for 2-10 days and compared it with normal saline control or with hydrocortisone alone (102129,102998,104027,104028,104032,105446). Although some subgroup analyses suggests that intravenous vitamin C alone in patients with sepsis may improve short-term mortality (106620,111298), other meta-analyses have not shown this benefit in subgroup analyses (111300). In addition, meta-analyses have identified significant publication bias (111298,111300). Long-term follow up from a study in patients with sepsis-induced respiratory and/or cardiovascular dysfunction shows that receiving HAT therapy does not improve cognitive, psychological, or functional status after 6 months and, for some domains, HAT therapy was worse when compared with placebo (111299). Studies evaluating intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, in mixed critically ill populations have also shown mixed findings. One such large meta-analysis of 27 randomized controlled trials and 21 observational studies shows that intravenous vitamin C reduces in-hospital mortality by 19% and ICU stay by about 1 day, but does not have a significant effect on hospital stay, mortality at 1 month, ICU mortality, or kidney injury, when compared with placebo or standard care. Also, effects on in-hospital mortality were no longer significant when data from randomized controlled trials were considered alone (106933). Other meta-analyses including 15-16 randomized controlled trials show that intravenous vitamin C, alone or as a component of HAT therapy, does not reduce overall, ICU, or in-hospital mortality when compared with control (106934,109957). A subgroup analysis in one of these analyses suggests that intravenous vitamin C as monotherapy, or in doses of at least 10 grams daily, may improve overall mortality (106934). Vitamin C also does not appear to benefit complications from sepsis, such as vasoplegic shock. A small clinical study in adults in the ICU with vasoplegic shock mostly secondary to sepsis and requiring moderate vasopressor support shows that administering intravenous vitamin C as sodium ascorbate 1.5 grams every 6 hours for 5 days or until cessation of vasoactive therapy does not reduce the duration of vasopressors, vasopressor dose, hospital or ICU length of stay, or mortality outcomes when compared with placebo (112475).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Atrophic acne scars. It is unclear if applying topical vitamin C after microblading improves atrophic acne scars. Details: A clinical study in adults with mild to severe atrophic acne scarring shows that applying a serum containing vitamin C 17% to the face after a once-monthly home microblade treatment for 4 months improves the appearance of acne scars at month 5 when compared with baseline (108086). Although this study enrolled a control group that used topical insulin in place of vitamin C, no between-group statistical comparisons were conducted, limiting the validity of this study.
• Age-related macular degeneration (AMD). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Most clinical research shows that taking the antioxidants vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily, with or without elemental zinc 80 mg, reduces the risk of visual acuity loss by 23% to 27% and reduces the risk of progression to advanced AMD at 5 years by 25% to 32% in patients at high risk for developing advanced AMD (7303,7304,11326,90069). The antioxidant plus zinc combination seems to reduce the risk of progression to advanced AMD in these patients more than taking the antioxidants without zinc (7303,90069). There is not enough evidence to know if taking the antioxidants or antioxidants plus zinc prevents progression to advanced AMD in patients with early stage AMD (7303,7304). The effect of vitamin C intake on developing AMD is unclear. Some population studies have found no association between dietary or supplemental vitamin C intake on risk of developing AMD (14007,14257). In one population study, vitamin C intake was associated with increased odds of developing age-related maculopathy (9823); however, in another population study, intake of vitamin C along with other antioxidants and zinc was associated with a reduced risk of AMD (14257). More evidence is needed to determine what role, if any, vitamin C intake has on the risk of developing AMD.
• Aging skin. Topical vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females aged 30-65 years shows that applying a specific liquid (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% to the face nightly for 8 weeks, in addition to regular facial skin products, improves skin color, elasticity, radiance, smoothness, and appearance of wrinkles when compared with regular facial skin products alone (102355).
• Albuminuria. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking vitamin C 1250 mg plus vitamin E 680 IU daily for 4 weeks can reduce the excretion of albumin by about 19% when compared with placebo in patients with type 2 diabetes (10434).
• Allergic rhinitis (hay fever). It is unclear if oral vitamin C is beneficial in patients with hay fever. Details: Epidemiological research has found that higher vitamin C plasma levels are not associated with a decreased risk of allergic rhinitis (15200). However, clinical research shows that some forms of vitamin C might help. In one small clinical study, intranasal vitamin C administered three times daily for 2 weeks reduces nasal secretions, nasal blockage, and edema in up to 74% of patients with perennial allergic rhinitis (15201). Another small clinical study in patients with seasonal allergic rhinitis shows that taking a single oral dose of vitamin C 2 grams reduces bronchial responsiveness to histamine at one hour after ingestion (15202). However, in another small study in patients with seasonal allergic rhinitis taking vitamin C orally in doses up to 4 grams daily for 3 days does not appear to suppress cutaneous or nasal response to histamine when compared to placebo (15203).
• Alzheimer disease. It is unclear if dietary vitamin C helps to prevent this condition. Details: Most epidemiological research has found that dietary intake of vitamin C is associated with a 17% reduced risk of developing Alzheimer disease (4636,9824,10131,13165,90082).
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral vitamin C helps to prevent ALS. Details: Observational research has found that increased dietary or supplemental intake of vitamin C is not associated with risk of developing ALS (90412).
• Anthracycline cardiotoxicity. Although there is interest in using oral vitamin C for anthracycline-induced cardiac toxicity, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Aspirin-associated gastric damage. It is unclear if oral vitamin C helps to prevent gastric damage caused by aspirin. Details: Some clinical research shows that vitamin C 480 mg might prevent gastric damage associated with taking aspirin 400 mg by decreasing blood loss and preventing decreased gastric blood flow (10357). However, a small clinical study in healthy patients shows that taking vitamin C 500 mg as ascorbic acid with aspirin 600 mg actually increases gastrointestinal permeability to a greater extent than either ingredient taken alone (98781).
• Athletic performance. It is unclear if oral vitamin C improves athletic performance. Details: Although some small preliminary clinical studies suggest that vitamin C might improve certain biomarkers during exercise (82922), a meta-analysis of small clinical trials in older and younger adults shows that taking vitamin C 500-1000 mg daily, with or without vitamin E, does not improve endurance, lean mass, or muscle strength when compared with placebo (102973). A more recent, small clinical study in recreationally trained males shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg daily for 10 weeks while participating in a resistance training program does not improve measures of muscle strength when compared with placebo (109959).
• Atopic disease. It is unclear if dietary vitamin C helps to prevent atopic disease. Details: Population research has found that higher intake of vitamin C is not associated with a reduced risk of eczema, wheeze, IgE-mediated food allergy, or allergic sensitization (90098).
• Attention deficit-hyperactivity disorder (ADHD). Small clinical studies suggest that high-dose oral vitamin C may not improve symptoms in patients with ADHD. Details: Some research suggests that taking megadose vitamins, including vitamin C, does not improve ADHD symptoms (9957,9958,9959). However, other preliminary clinical research shows that taking 25 mg of vitamin C in combination with flaxseed oil providing alpha-linolenic acid 200 mg twice daily might improve measures of attention, impulsivity, restlessness, and self-control in children with ADHD when compared with baseline (14443). It is not clear if these effects are due to vitamin C, flaxseed oil, or the combination.
• Autism spectrum disorder. It is unclear if oral vitamin C is beneficial in patients with autism spectrum disorder. Details: One small clinical study shows that taking vitamin C 8 grams per 70 kg daily for 10 weeks modestly reduces autism symptom severity in school children when compared with placebo (83604).
• Bleeding. It is unclear if intravenous vitamin C can reduce bleeding after total abdominal hysterectomy. Details: A small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery reduces postoperative hemorrhage volume by around 40 mL when compared with placebo (109465).
• Brain tumor. It is unclear if oral vitamin C helps to prevent brain tumors. Details: Population research has found that vitamin C intake is associated with a 14% reduced risk of glioma. This risk reduction was more prevalent in America compared to other geographic locations (98782).
• Breast cancer. It is unclear if oral vitamin C helps to prevent breast cancer, its recurrence, or breast cancer-related mortality. Details: Some epidemiological research has found that dietary vitamin C is associated with a reduced risk of breast cancer (1444,10823,10824). However, other epidemiological research has found no association with dietary or supplemental vitamin C (10825,10826,108080). One cohort study found no association between breast cancer risk and total, dietary, or supplemental vitamin C, regardless of dose, treatment duration, or formulation (single ingredient or combination product). Additionally, hormone and menopausal status did not appear to impact risk. Vitamin C intake might be associated with a reduced risk in individuals with a family history of breast cancer in first-degree relatives (108080). In patients with breast cancer, supplemental or dietary intake of vitamin C might be associated with a reduced risk of mortality. A meta-analysis of results from population research shows that vitamin C supplementation following breast cancer diagnosis is associated with a 15% lower risk of breast cancer-related mortality when compared with no supplementation (90416). A large, observational study in patients with breast cancer undergoing radiation therapy has found that vitamin C supplementation does not reduce the risk of breast cancer recurrence over a period of 5 years when compared with no supplementation. Although the vitamin C group had notably less aggressive tumor types, recurrence-free survival was similar in both vitamin C and control groups (108082). The validity of these findings is limited due to unknown doses of vitamin C and the inclusion of various breast cancer subtypes.
• Burns. Small studies suggest that intravenous vitamin C may modestly improve symptoms in patients with severe burns. Details: A small clinical study in patients with severe burns shows that administering vitamin C intravenously (IV) 66 mg/kg hourly over 24 hours, as part of fluid resuscitation using lactated ringer solution, reduces wound edema and the volume of fluid needed when compared with fluid resuscitation alone (83145). A retrospective review of adults hospitalized with severe burns has found that those who receive a continuous IV infusion of at least 10 grams of vitamin C within 2 days of admission have an in-hospital mortality rate of 46%, compared with 58% for those who do not receive vitamin C (102128).
• Cancer. It is unclear if oral or intravenous vitamin C helps to prevent cancer or cancer-related mortality. Details: Some population research has found that DIETARY intake of vitamin C is linked with a lower risk of cancer and cancer-related mortality (3910,5878,10819,109779). However, clinical research shows that taking vitamin C SUPPLEMENTS does not reduce the risk for cancer (10819,14109,34580,90097). In people with cancer, although some clinical research has shown that taking high-dose vitamin C supplements can improve survival rates (9809,96704), other clinical research has not shown this benefit (4842,4843). In 2003, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that some scientific evidence suggests that antioxidant vitamins, such as vitamin C, may reduce the risk of certain forms of cancer. However, the FDA has determined that there is little scientific evidence supporting this claim (102334). Preliminary clinical research has also evaluated vitamin C supplements in patients with cancer. High-dose oral vitamin C, 10 grams daily, in patients with advanced cancer does not seem to improve survival or decrease disease progression (4842,4843,106617). However, preliminary clinical research suggests high doses of vitamin C, given intravenously, might have a beneficial effect on some outcomes, including survival rate in some patients with cancer (9809,96704,106617). However, there is no benefit to other patients studied in the case reports and this has not been tested in well-designed clinical trials (9809,96704).
• Carpal tunnel syndrome. Vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamins C, E, B1, B2, B6, and B12, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, and turmeric twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with control (111702). The validity of these effects is limited by a lack of blinding. The study may also be inadequately powered to detect a difference between groups. Additionally, it is unclear if the effects are due to vitamin C, other ingredients, or the combination.
• Cataracts. It is unclear if oral vitamin C helps to prevent cataracts. Details: Population research has found that people with the highest total intake of vitamin C have about a 19% reduced risk of developing cataracts when compared with those with the lowest total intake. The greatest benefit is observed for nuclear cataracts (96711). A separate study found that higher supplemental intake of vitamin C for 10 years is associated with a 60% reduction in the incidence of nuclear and cortical cataracts (4208). Other population research has found that the highest blood levels of vitamin C are associated with a 33% reduced odds of developing age-related cataract, but any benefit seems to be limited to Asian populations (90944). One prospective clinical study shows that taking vitamin C plus vitamin E and beta-carotene does not prevent the development or progression of age-related loss of vision due to cataracts in well-nourished people taking the supplement for an average of 6.3 years (7304).
• Cervical cancer. It is unclear if oral vitamin C helps to prevent cervical cancer. Details: Observational research has found that higher vitamin C intake is associated with a 33% to 42% reduced odds of cervical neoplasm. Increasing vitamin C intake by 50 mg daily is associated with an 8% reduced odds of cervical neoplasm (34609,98771).
• Chronic fatigue syndrome (CFS). Although there is interest in using oral vitamin C for CFS, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Colistin-induced nephrotoxicity. It is unclear if intravenous vitamin C helps to prevent nephrotoxicity from colistin. Details: A small clinical study shows that intravenous administration of vitamin C 2 grams every 12 hours along with colistin for around 9-10 days does not prevent nephrotoxicity when compared with colistin therapy alone (99839). However, this study was limited by a lack of statistical power to detect differences between the study groups.
• Contrast induced nephropathy. It is unclear if oral vitamin C helps to prevent contrast-induced nephropathy (CIN). Details: Some clinical research shows that taking vitamin C before and after coronary angiography reduces the risk of developing CIN by 33% to 55% when compared with placebo in patients with renal dysfunction (12234,90421). However, other clinical evidence published since 2012 suggests that vitamin C given orally and/or intravenously before and after angiography does not reduce the risk of CIN compared with control in high-risk patients with chronic renal insufficiency or diabetes (91232,91236,90410,90425). Reasons for the discrepancies are not entirely clear. However, it is possible that the lack of significant benefit from vitamin C in the latter studies results from the fact that incidences of CIN have become less common than in the past due to avoidance of dehydration, use of smaller catheters, and use of contrast agents with reduced nephrotoxicity (90429).
• Coronary artery bypass graft (CABG) surgery. It is unclear if intravenous vitamin C helps to improve patient outcomes after CABG surgery. Details: A small clinical study shows that giving vitamin C 5 grams intravenously (IV) before anesthesia induction and 5 grams in the cardioplegia solution used during surgery shortens the length of stay in the intensive care unit (ICU) by about 8 hours (102127). However, some limited research suggests that IV vitamin C does not resolve cardiac surgery complications. A small clinical study in patients with vasoplegia after receiving CABG and other cardiac surgeries shows that receiving IV vitamin C 1.5 grams every 6 hours after being admitted to the ICU does not improve vasoplegia when compared with control (102981).
• Delirium. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research in adults with septic shock has found that receiving intravenous thiamine 400 mg daily with vitamin C 6 grams daily, both in divided doses, is not associated with reduced delirium when compared with control (103001).
• Dental plaque. It is unclear if vitamin C in a chewing gum helps to reduce dental plaque formation. Details: A small clinical study in patients with calculus shows that chewing 10 pieces of gum, each containing 60 mg of vitamin C, daily for 3 months reduces the formation of dental calculus, visible plaque, and the number of bleeding sites when compared not chewing gum (83303). The validity of this finding is limited by a lack of placebo group.
• Depression. It is unclear if oral vitamin C is beneficial for the treatment or prevention of depression. Details: A small clinical study in children and adolescents shows that taking vitamin C 500 mg orally twice daily in combination with fluoxetine 10-20 mg daily for 6 months reduces most symptoms of major depressive disorder when compared with taking fluoxetine alone (90404). However, a small clinical study in adults shows that taking vitamin C up to 1000 mg daily for 2 months does not improve the response rate or decrease symptoms of depression in adults also taking citalopram when compared with citalopram alone (96708). Reasons for these conflicting results may relate to the age of the patients, study duration, or differences in antidepressant medication being taken. One clinical guideline also provisionally recommends against the use of oral vitamin C to treat patients with depression based on low-quality evidence (110318). Some research has also evaluated vitamin C intake for the prevention of depression. A secondary analysis of pre- and peri-menopausal adults enrolled in the Study of Women's Health Across the Nation (SWAN) program suggests that vitamin C intake is inversely associated with depressive symptoms. This association persisted regardless of age, race, physical activity, body mass index, antidepressant use or menopausal status (108083). The validity of these findings is limited due to the secondary nature of this study; additionally, follow-up time is unclear.
• Diabetes. It is unclear if oral vitamin C prevents diabetes. Some low-quality research suggests that vitamin C might improve glycemic control in patients with diabetes. Details: Population research has not found a link between dietary vitamin C and the risk of developing type 2 diabetes (14004). However, low certainty clinical research has found some benefit of taking vitamin C supplements for glycemic control. Two meta-analyses of several small, heterogeneous clinical studies in patients with type 2 diabetes show that taking vitamin C 200-3000 mg daily for 2-48 weeks reduces fasting blood glucose by approximately 11 mg/dL (112478) and glycated hemoglobin (HbA1c) by an average of 0.5% when compared with placebo, standard treatment, or no treatment (105461,112478). Subgroup analyses suggest that durations of supplementation longer than 12 weeks show greater glycemic benefit, and although one meta-analysis suggests there is no dose-response relationship (105461), another meta-analysis suggests that doses of vitamin C 1000 mg and higher are most beneficial for improving glycemic indices (112478). Some research has evaluated the effects of vitamin C supplementation on the lipid profile in patients with diabetes, with mixed findings. One meta-analysis of 17 small clinical studies shows that taking vitamin C 200-3000 mg daily for 2 to 48 weeks improves levels of triglycerides and total cholesterol, but not low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. Subgroup analysis suggests that study durations of at least 12 weeks show greater benefit (106621). However, two other meta-analyses in patients with diabetes, one of 16 small heterogenous clinical studies and one of 11 small clinical studies, show no clinically important improvement in lipid levels after vitamin C supplementation (105461,105464).
• Dry mouth. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical trial in patients receiving radiotherapy for head and neck cancer shows that taking vitamin E 100 IU and vitamin C 500 mg twice daily for an average of 3 months improves dry mouth when compared to baseline (99080). The validity of these results is limited by the lack of comparison with a control group.
• Endometrial cancer. Increased dietary vitamin C has been linked to reduced risk of endometrial cancer. Details: Population research has found that intake of vitamin C from dietary sources is associated with a slightly decreased risk of endometrial cancer when compared with control. However, this benefit is not observed when results from a prospective cohort study are assessed (34578).
• Endometriosis. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with endometriosis and pelvic pain shows that taking vitamin C 1000 mg and vitamin E 800 IU daily for 8 weeks improves dysmenorrhea, dyspareunia, and chronic pelvic pain scores when compared with placebo. Vitamin C and vitamin E supplementation also reduces some biochemical markers of oxidative stress when compared with placebo (106622).
• Endoscopy-associated adverse effects. It is unclear if a topical vitamin C spray reduces mucosal irritation in patients undergoing Lugol chromoendoscopy. Details: A small clinical trial in patients receiving a Lugol chromoendoscopy shows that spraying a vitamin C 2% solution after the application of the Lugol iodine 2% solution reduces the severity of mucosal irritation, heartburn, and pain when compared with using a normal saline spray after the Lugol iodine 2% solution (104030).
• Esophageal cancer. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Population research has found that higher dietary intake of vitamin C is associated with reduced odds of esophageal adenocarcinoma. A 50 gram increase in dietary vitamin C intake is associated with a 13% reduced odds of esophageal cancer (34551,98770). However, a meta-analysis of clinical research shows that taking a vitamin C supplement in combination with beta-carotene and vitamin E does not reduce the risk of esophageal cancer (34581).
• Exercise-induced asthma. Small clinical studies suggest that oral vitamin C may modestly improve symptoms in patients with exercise-induced asthma. Details: A meta-analysis of the available clinical research shows that vitamin C supplementation might reduce exercise-induced breathlessness when compared with placebo or control. However, the available research is of poor quality, and no clear conclusions can be drawn regarding its benefits for exercise-induced asthma (90409).
• Exercise-induced muscle damage. It is unclear if oral vitamin C is beneficial in exercise-induced muscle damage. Details: A small clinical study in healthy females shows that taking vitamin C 1000 mg before moderate intensity cycling does not prevent muscle damage when compared with placebo (99837). Another small clinical study in endurance-trained runners shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg 2 hours prior to an exercise protocol does not reduce delayed onset muscle soreness or improve other markers of exercise-induced muscle damage when compared with placebo (109961).
• Gallbladder disease. It is unclear if oral vitamin C reduces the risk of gallbladder disease. Details: Cross-sectional epidemiological evidence has found that vitamin C supplementation and increased vitamin C serum levels are associated with a decreased risk of developing gallbladder disease in females, but not males (5877).
• Gastric cancer. It is unclear if dietary or supplemental vitamin C reduces the risk of gastric cancer. Details: Most population research has not found an association between DIETARY intake of vitamin C and gastric cancer risk (9194,10822,10819,90083). Also, clinical research shows that taking vitamin C supplements in combination with other antioxidants does not reduce the risk of gastric cancer or precancerous gastric lesions (14447,34581,90085). However, some research suggests that it might be associated with a reduced risk for specific forms of gastric cancer (9838,90083). One clinical study shows that taking vitamin C orally 500 mg daily for 6 months after eradication of Helicobacter pylori infection decreases the incidence of precancerous changes in stomach tissue when compared with no treatment (10359). Also, other clinical research shows that taking vitamin C orally 1 gram daily helps promote the regression of precancerous gastric lesions in people at high risk for gastric cancer (2579). In 2009, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that vitamin C supplements may reduce the risk of gastric cancer. However, the FDA has concluded that it is highly uncertain that vitamin C supplements actually reduce the risk of gastric cancer (102332).
• Gastritis. There is limited evidence on the oral use of vitamin C in omeprazole-induced corpus gastritis. Details: A small clinical study shows that taking vitamin C orally 1200 mg daily along with omeprazole decreases corpus gastritis associated with omeprazole therapy in patients with H. pylori infection (10360).
• Gout. It is unclear if oral vitamin C helps to prevent or manage gout. Details: Population research in men has found that taking vitamin C 500-1500 mg daily from the diet and/or supplements is associated with up to a 34% reduced risk of gout when compared with less than 250 mg daily (16755). Also, men who ingest over 500 mg of vitamin C daily from the diet and supplements have serum uric acid levels that are slightly lower than men who consume less than 90 mg daily (16820). However, taking supplemental vitamin C 500 mg daily for 8 weeks does not seem to lower serum uric acid levels in patients who already have gout (90423).
• Hearing loss. There is limited evidence on the intravenous use of vitamin C in idiopathic sudden sensorineural hearing loss. It is unclear if dietary vitamin C intake can affect the risk of hearing loss. Details: A small clinical study in patients with idiopathic sudden sensorineural hearing loss shows that receiving intravenous high-dose vitamin C 200 mg/kg daily in combination with steroid therapy for 10 days, followed by oral vitamin C 2000 mg daily for 30 days, increases recovery rate two-fold and modestly improves hearing threshold levels when compared with receiving steroid therapy only (90417). In addition, population research in females has found that high dietary intake of vitamin C is associated with a 22% increased risk of developing self-reported hearing loss over a 22-year period when compared with low intake (109807).
• Heart transplant complications. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial shows that a combination of vitamin C 500 mg and vitamin E 400 IU, taken twice daily for 1 year starting within the first 2 years after cardiac transplant, reduced the progression of vasculopathy as measured by intravascular ultrasonography (IVUS) when compared with placebo. This suggests that the combination may help slow the progression of CAV (82826).
• Hepatitis C. It is unclear if oral vitamin C is beneficial in patients with hepatitis C. Details: A small clinical study in patients with confirmed hepatitis C shows that taking vitamin C 1000 mg daily with conventional therapy (sofosbuvir plus daclatasvir) for 4 weeks improves serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, and albumin when compared with conventional therapy alone (109463).
• HIV/AIDS. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, low-quality study in men with HIV shows that taking vitamin C 250 mg daily in combination with vitamin A, beta-carotene, vitamin E, selenium, and coenzyme Q10 does not improve viral load, although it seems to improve markers of oxidative stress when compared to baseline. However, a 1000 mg dose of vitamin C, as well as higher doses of the other antioxidants, do not seem to provide any additional effect (9830).
• HIV transmission. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in HIV-positive mothers shows that taking vitamin B, vitamin C, and vitamin E daily during pregnancy and while breast-feeding for 20 weeks seems to reduce child mortality and HIV transmission through breast milk when compared with taking vitamin A (9801).
• Hyperphosphatemia. Intravenous vitamin C might be beneficial for reducing phosphate levels in patients with end-stage renal disease. Details: A small clinical study in hemodialysis patients with elevated phosphorus levels suggests that administering vitamin C 500 mg intravenously three times weekly for 8 weeks reduces phosphorus levels about seven-fold when compared with placebo (90414).
• Idiopathic interstitial pneumonia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with idiopathic pulmonary fibrosis, a form of idiopathic interstitial pneumonia, shows that taking a combination of vitamin C 250 mg every other day, vitamin D 50,000 IU daily, and vitamin E 200 IU daily for 12 weeks improves some, but not all, measures of lung function and reduces markers of inflammation and oxidative stress when compared to baseline (109464). The validity of these findings is limited by a lack of placebo control group.
• Infertility. It is unclear if oral vitamin C is beneficial in anovulatory females. Details: A very small clinical study suggests that taking vitamin C 400-1000 mg daily might improve fertility, resulting in ovulation and pregnancy in some anovulatory females, when compared with baseline (14018). The validity of these findings is limited by the small study size and lack of a comparator group.
• Male infertility. It is unclear if oral or intravenous vitamin C is beneficial in males with infertility. Details: A meta-analysis of three small, low-quality clinical trials in males with infertility shows that taking vitamin C up to 1000 mg daily for up to 12 weeks can improve sperm count, motility, and vitality, but does not seem to increase semen volume or sperm concentration, when compared with control (109461). It is unclear if vitamin C can increase pregnancy rates, as these studies did not assess this outcome. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing vitamin C 90 mg, zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, coenzyme Q10 20 mg, folic acid 0.2 mg, selenium 0.05 mg, and vitamin B12 0.015 mg (Proxeed Plus, Sigma-Tau) orally twice daily for 6 months improves sperm count, sperm concentration, and sperm motility when compared with baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles. The validity of this study is limited by the lack of a comparator group (111296).
• Mastalgia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with mastalgia shows that taking a combination of vitamin C 100 mg, vitamin B12, and gamma-linolenic acid daily for 12 weeks does not improve the proportion of patients with minimal or no pain when compared with placebo (111059).
• Melasma. It is unclear if topical vitamin C is beneficial in patients with melasma. Details: A small clinical study in patients with bilateral symmetrically distributed facial melasma shows that topical application of 0.5 mL of vitamin C (Cosmotech, Alpha Medical Cosmotech) following dermapen microneedling every 2 weeks for 6 weeks is similarly effective to tranexamic acid for improving melasma severity and pigmented, but not vascular, findings on dermoscopic examination (106939).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin C is beneficial in patients with NAFLD. Details: A clinical study in patients with NAFLD shows that taking vitamin C 250 mg, 1000 mg, or 2000 mg daily for 12 weeks improves some biochemical markers of liver health and glucose metabolism when compared with baseline. However, the improvement from baseline was similar between groups (106942).
• Nonalcoholic steatohepatitis (NASH). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research suggests vitamin C in combination with vitamin E might improve hepatic fibrosis in patients with NASH. However, it does not seem to decrease liver inflammation (14005).
• Non-Hodgkin lymphoma. It is unclear if oral vitamin C reduces the risk of developing diffuse large B-cell lymphoma. Details: In one population study, higher dietary or supplemental intake of vitamin C was associated with a reduced risk of diffuse large B-cell lymphoma, a type of non-Hodgkin lymphoma, when compared with lower intake in postmenopausal adults (90945).
• Oral cancer. It is unclear if oral vitamin C reduces the risk of developing oral cancer. Details: Population research has found that higher dietary intake of vitamin C is associated with a reduced risk of oral cancer (10821). However, clinical research has not shown benefit with oral vitamin C supplements. A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Oral leukoplakia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not improve leukoplakia symptoms or reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Osteoarthritis. It is unclear if dietary vitamin C reduces the risk of developing osteoarthritis. Details: Observational research has found that increased vitamin C from dietary sources is associated with a reduced risk of cartilage loss and disease progression in people with osteoarthritis (5881).
• Osteoporosis. It is unclear if dietary vitamin C improves bone density or reduces fracture risk in patients at risk for osteoporosis. Details: Some cross-sectional observational research in postmenopausal patients without a history of smoking or estrogen use has found that higher serum vitamin C levels are associated with lower bone mineral density (9828). However, other observational research in a larger population of adults at risk for osteoporosis has found that higher dietary vitamin C intake is not associated with fracture risk (104415).
• Ovarian cancer. Dietary vitamin C might not affect the risk of ovarian cancer. Details: Epidemiological research has found that dietary vitamin C intake is not linked with ovarian cancer risk (9193,102977).
• Pancreatitis. It is unclear if intravenous vitamin C is beneficial in patients with acute pancreatitis. Details: A small meta-analysis of clinical studies in patients with acute pancreatitis shows that intravenous vitamin C does not improve the odds of developing organ failure when compared with placebo or no intervention. Intravenous vitamin C seems to reduce hospital stay, but not in-hospital mortality (106941).
• Parkinson disease. Dietary vitamin C might not affect the risk of developing this condition. Details: Observational research has found that moderate or high dietary intake of vitamin C is not associated with a reduced risk of Parkinson disease (83316).
• Periodontitis. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is also unclear if dietary vitamin C reduces the risk of periodontitis. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a supplement containing vitamin C 100 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin E, and zinc twice daily for 8 weeks in addition to standard nonsurgical therapy does not improve periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation, among others, when compared with placebo (111708). It is unclear if these effects are due to vitamin C, other ingredients, or the combination. There is also interest in whether dietary vitamin C intake impacts the risk of periodontitis. Observational research in US adults has found that individuals with dietary intake of vitamin C in the third quartile, but not the second or fourth quartiles, have lower odds of periodontitis when compared with vitamin C intake in the lowest quartile. Furthermore, the investigators identified a non-linear relationship between vitamin C intake and periodontitis risk, suggesting that individuals with intakes either much lower or much higher than 158 mg daily are at increased risk of developing periodontitis (109958).
• Peripheral arterial disease (PAD). It is unclear if dietary vitamin C helps to reduce the risk of developing PAD. Details: In females, epidemiological evidence has found that dietary intake of vitamin C of 142 mg daily or greater is associated with a 36% reduced risk of PAD when compared with lower intake levels of less than 80 mg daily (10130).
• Physical performance. It is unclear if oral vitamin C helps to improve physical performance and muscle strength in older people. Details: Population research has found that higher intake of dietary vitamin C is associated with improved physical performance and muscle strength in elderly people (14006). In contrast, a small clinical study in elderly men undergoing strength training shows that taking vitamin C 1000 mg and vitamin E 258IU daily for 12 weeks does not increase strength, and might even attenuate increases in muscle mass, when compared with strength training alone (96701).
• Pneumonia. It is unclear if oral vitamin C helps to prevent pneumonia. Details: A meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the occurrence of pneumonia when compared to control (104033).
• Postoperative recovery. It is unclear if oral or intravenous vitamin C improves postoperative recovery. Details: Meta-analyses of clinical research show that oral or intravenous vitamin C can shorten the duration of hospitalization after cardiac surgery when compared with control (91233,96703). However, other research shows no decrease in intensive care or hospital stay with vitamin C supplementation (96705). A meta-analysis of 37 clinical trials in adults undergoing low- to high-risk noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, or kidney transplantation), shows that receiving perioperative vitamin C, either orally or intravenously, does not improve duration of hospitalization or overall mortality when compared with control (108087). There's also some limited evidence that vitamin C might reduce postoperative pulmonary complications such as lung infection, pleural effusion, and pneumothorax. A small clinical trial in low-risk cardiac surgery patients shows that receiving intravenous vitamin C 1 gram 10 minutes after anesthesia might slightly reduce the rate of postoperative pulmonary complications when compared with receiving a saline injection (104034).
• Premature rupture of membranes (PROM). Oral vitamin C seems to reduce the risk of PROM in some patients; however, the addition of oral vitamin E seems to negate any benefit. Details: A meta-analysis of clinical research shows that taking vitamin C alone decreases the risk of both term and preterm PROM by 45% and 34%, respectively, when compared with placebo or control (96707). Also, a more recent clinical study in patients with a history of PROM shows that taking vitamin C 100 mg daily, starting at 14 weeks' gestation, increases the gestational age at recurrent PROM by around 1 week and increases the gestational age at birth by around 1.3 weeks when compared with placebo (109960). Taking vitamin C in combination with vitamin E, however, does not seem to reduce the risk of term or preterm PROM; some research suggests that it might even increase the risk of non-preterm PROM (83472,96707). However, other research shows that taking vitamin C 1000 mg plus vitamin E 400 IU daily, beginning at 24 to 34 weeks gestation and continuing until delivery, may help increase the latency period until delivery by 5 days and increase gestational age at delivery by almost 1 week when compared with placebo in patients with preterm PROM (90078).
• Pressure ulcers. It is unclear if oral vitamin C, when used alone or in combination with other ingredients, can improve the healing of pressure ulcers. Details: A small clinical study in institutionalized patients with pressure ulcers shows that taking vitamin C 500 mg twice daily for 12 weeks does not improve wound closure or increase healing rates when compared with vitamin C 10 mg twice daily (83617). Oral vitamin C has also been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients with pressure ulcers shows that administering an oral nutritional supplement enriched with vitamin C, L-arginine, and zinc improves ulcer healing when compared with a standard diet (31953,87173). Also, clinical research in patients living in long-term care facilities shows that taking an oral nutritional supplement enriched in protein, vitamin C, L-arginine, and zinc daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
• Radiation proctopathy. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with chronic radiation proctitis shows that vitamin C 500 mg plus vitamin E 400 IU three times daily might improve symptoms when compared with baseline (9825). The validity of these findings is limited by the lack of a comparator group.
• Renal cell carcinoma. It is unclear if increased dietary intake of vitamin C helps to reduce the risk of renal cell carcinoma. Details: Population research has found that increased dietary intake of vitamin C is associated with a 12% reduced risk of renal cell carcinoma (98779).
• Respiratory tract infections. It is unclear if oral vitamin C is beneficial for preventing respiratory tract infections or reducing the duration of these infections. Details: A meta-analysis of clinical research in children and adults shows that, when compared with placebo, oral vitamin C supplementation reduces the average number of symptomatic days per individual, but does not reduce the average symptom days per respiratory episode. Also, vitamin C intake does not reduce the incidence or severity of respiratory disease or improve recovery in hospitalized patients with respiratory tract infections (108077). The validity of this trial is limited by the high heterogeneity of included studies, which evaluated various vitamin C regimens, ranging from 100 mg to 8 grams daily, as preventive therapy or as an adjuvant to active treatment. A clinical study in children aged 3-10 years shows that taking vitamin C 50 mg in combination with a specific product (Lab4) containing Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium animalis subsp. lactis daily for 6 months reduces the incidence of cough and sore throat by 16% and 20%, respectively, when compared with placebo. However, it did not improve total symptoms, nasal congestion, nasal discharge, or sneezing. Also, aside from a 33% reduction in the average number of days with a sore throat, daily supplementation does not reduce the duration of individual symptoms or total symptoms (106943). It is unclear if these effects are due to vitamin C, the probiotics, or the combination.
• Restless legs syndrome (RLS). It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in hemodialysis patients with RLS shows that taking vitamin C 200 mg daily, alone or in combination with vitamin E 400 mg, for 8 weeks reduces the severity of RLS when compared with placebo (90093). More research is needed to determine if vitamin C is beneficial in treating RLS that is not associated with hemodialysis.
• Sunburn. Topical and oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking vitamin C orally in combination with vitamin E seems to prevent ultraviolet (UV) radiation-induced erythema (sunburn) (4715,4716). Vitamin C in combination with high dose oral RRR-alpha-tocopherol (natural vitamin E) seems to protect against skin inflammation after exposure to UV radiation (4715). Also, applying topical vitamin C in combination with topical vitamin E and melatonin seems to provide modest photoprotective effects when used prior to UV exposure. However, it has no effect when used during or after UV exposure (4713,4714).
• Stress. It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in healthy adults shows that taking vitamin C 3000 mg daily for 14 days modestly reduces blood pressure and subjective stress response to psychological stress when compared with placebo (10353).
• Stroke. Observational research has found that although taking vitamin C supplements does not seem to be beneficial, eating more vitamin C-rich food is linked with reduced risk of stroke. Details: Lower plasma levels of vitamin C have been associated with increased stroke risk (90408). Additionally, population research has found that higher dietary intake of vitamin C is associated with a 8% to 19% reduction in stroke risk when compared to lower intake (90408,109779). This reduction appears to be dose-dependent, with each 100 mg/day increase in dietary vitamin C intake associated with about a 17% reduction (90408). However, taking vitamin C supplements has not been found to be associated with reduced stroke risk (1449,90408).
• Tetanus. It is unclear if intravenous vitamin C helps to reduce symptoms of tetanus. Details: A low quality clinical trial in children and young adults with tetanus shows that intravenous vitamin C 1 gram daily along with conventional treatment reduces fatality when compared to control (21539).
• Tooth extraction. It is unclear if oral vitamin C is beneficial for reducing pain or improving healing after tooth extraction. Details: A small clinical study in healthy patients aged 14-41 years who are undergoing bilateral premolar extraction shows that taking vitamin C 200 mg three times daily, beginning immediately after extraction and continued for 10 days, improves pain on days 1-3, and may reduce mesio-distal wound size between days 1 and 7, when compared with placebo, but not when compared with vitamin C 500 mg three times daily. A dose of 500 mg three times daily did not improve pain scores or extraction wound healing when compared with placebo (108084). The validity of this trial is limited by the short duration of treatment; additionally, this study did not report baseline vitamin C levels.
• Urinary tract infections (UTIs). Although there is interest in using oral vitamin C for UTIs, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Vascular dementia. It is unclear if oral vitamin C reduces the risk of vascular dementia. Details: Population research has found that supplemental intake of vitamin C and vitamin E is associated with a reduced risk of vascular dementia in Japanese-American men (4636). However, when cases in which dementia was diagnosed prior to the study are excluded from data analysis, intake of vitamin C and vitamin E is not associated with a reduced risk of vascular dementia in these patients (9824).
• Wound healing. It is unclear if oral vitamin C improves the healing of chronic foot ulcers. It is also unclear if intravenous vitamin C improves healing of surgical wounds after total abdominal hysterectomy. Details: A very small clinical study in adults with chronic foot ulcers shows that taking slow-release vitamin C 500 mg daily for 8 weeks seems to result in a median of 100% ulcer healing, compared with a median of 14% ulcer healing in patients taking glucosamine 1000 mg daily (105456). This finding is limited due to the small and heterogeneous patient population, which included patients with diabetes, vascular disease, and/or vitamin C deficiency. Another small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery does not reduce the rate of surgical site infection or wound dehiscence when compared with placebo (109465). However, this study may not have been adequately powered to detect differences between groups. More evidence is needed to rate vitamin C for these uses.

(Read more about VITAMIN C)

POSSIBLY EFFECTIVE

• Constipation. Taking xanthan gum orally as a bulk-forming laxative seems to decrease constipation (4917,4918).
• Swallowing dysfunction. Using a specific xanthan gum product (Resource ThickenUp Clear, Nestle Health Science) as a thickener in liquid feeds improves swallowing and reduces the risk of aspiration in people with swallowing dysfunction similarly to a modified starch thickener (Resource ThickenUp, Nestle Health Science). Xanthan gum also does not appear to leave the pharyngeal residues seen with the modified starch product (100912,100913).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Diabetes. Taking xanthan gum 12 grams orally daily in muffins seems to lower blood glucose in people with diabetes (4916).
• Dry eye. Using eye drops containing xanthan gum and chondroitin sulfate (PRO-148 or Xiel ofteno, Sophia Laboratories) four times daily for 60 days improves tear film break-up times, ocular surface disease index, and symptoms of dry eye similarly to polyethylene glycol/propylene glycol eye drops (Systane, Alcon Laboratories Inc.) (89591,95794). It is not clear if this effect is due to xanthan gum, chondroitin sulfate, or the combination.
• Sjogren syndrome. Applying xanthan gum topically in the mouth seems to help as a saliva substitute in people with Sjogren syndrome (4915).

(Read more about XANTHAN GUM)

LIKELY SAFE ...when used orally in amounts typically found in foods (11). There is insufficient reliable information available about the safety of algin when used orally in medicinal amounts.

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about ALGIN)

POSSIBLY SAFE ...when non-contaminated species of spirulina blue-green algae are used orally and appropriately (91713). The blue-green algae species Arthrospira platensis has been used with apparent safety in doses up to 19 grams daily for 2 months, or 10 grams daily for 6 months (18296,18300,18306,75944,91705,99703,104567,109965). The blue-green algae species Arthrospira fusiformis has been used with apparent safety in doses up to 4 grams daily for 3 months, or 1 gram daily for 12 months (15782,91717). Another blue-green algae species, Arthrospira maxima, has been used with apparent safety in a dose of 4.5 grams daily for up to 12 weeks (18297,99654,99655,102688). ...when non-contaminated, non-toxin producing strains of blue-green algae from the Aphanizomenon flos-aquae species are used orally and appropriately. Doses up to 1.6 grams daily have been used with apparent safety for up to 6 months (14842,18310). Some blue-green algae species can produce toxins called microcystins. According to the World Health Organization (WHO), the tolerable daily intake of microcystins in adults is 0.04 mcg/kg (96549).

POSSIBLY UNSAFE ...when contaminated blue-green algae are used orally. Blue-green algae can be contaminated with heavy metals (including mercury, cadmium, lead, or arsenic), neurotoxins, and toxic microcystin-producing cyanobacteria such as Microcystis aeruginosa (9171,75966,91704,91711,96550). Microcystins are most commonly reported in the blue-green algae species Aphanizomenon flos-aquae harvested from Upper Klamath Lake in Oregon. The Oregon Department of Health has set a limit of 1 mcg of microcystin-LR equivalents per gram dry weight of blue-green algae, assuming consumption of about 2 grams/day by adults (91704,91713). However, many samples of Aphanizomenon flos-aquae have been reported to contain higher levels than this (9171,91704). According to the World Health Organization (WHO), the tolerable daily intake of microcystins in adults is 0.04 mcg/kg (96549). When consumed orally, microcystins accumulate in the liver, binding to and inhibiting protein phosphatases, causing hepatocyte damage and possible tumor promotion (9171). Aphanizomenon flos-aquae can also produce neurotoxic compounds that may be present in supplements containing this organism (91704).

CHILDREN: POSSIBLY UNSAFE
when blue-green algae products are used orally. Blue-green algae can accumulate heavy metals such as lead and mercury (91704,91711). They can also contain toxic microcystins produced by contaminating species of cyanobacteria such a Microcystis aeruginosa (91704). Children are more sensitive to poisoning by microcystins (3536). The Oregon Department of Health has set a limit for microcystins of 1 mcg per gram dry weight of blue-green algae, but some countries have set very low exposure limits of 0.2 mcg per day and 0.8 mcg per day for infants and children, respectively (91704).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using. Some blue-green algae products, specifically those of the species Aphanizomenon flos-aquae, have been found to contain low amounts of beta-methylamino-L-alanine (BMAA). BMAA is associated with neurodegenerative diseases, and breast milk has been shown to be a potential source of BMAA exposure in infants (96550).

(Read more about BLUE-GREEN ALGAE)

LIKELY SAFE ...when used orally in amounts commonly found in foods. Brown rice has Generally Recognized as Safe (GRAS) status in the US (7705). There is insufficient reliable information available about the safety of brown rice when used orally in medicinal amounts.

CHILDREN: LIKELY SAFE
when used orally in amounts commonly found in food. Brown rice has Generally Recognized as Safe (GRAS) status in the US (7705). There is insufficient reliable information available about the safety of brown rice when used in medicinal amounts in children.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts commonly found in foods (7705). There is insufficient reliable information available about the safety of brown rice when used in medicinal amounts during pregnancy or lactation.

(Read more about BROWN RICE)

LIKELY SAFE ...when used orally or intravenously and appropriately. Calcium is safe when used in appropriate doses (7555,12928,12946,95817). However, excessive doses should be avoided. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stone, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients not to consume more than the recommended daily intake of 1000-1200 mg per day and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (93533).

POSSIBLY UNSAFE ...when used orally in excessive doses. The National Academy of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 19-50 years, 2500 mg; 51 years and older, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients to not consume more than the recommended daily intake of 1000-1200 mg per day and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (93533).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Calcium is safe when used in appropriate doses (17506).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (945,1586,3263,3264,17506). The World Health Organization (WHO) recommends prescribing oral calcium supplementation 1.5-2 grams daily during pregnancy to those with low dietary calcium intake to prevent pre-eclampsia (97347).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the same daily tolerable upper intake level (UL) for calcium according to age independent of pregnancy status: 9-18 years, 3000 mg; 19-50 years, 2500 mg (17506). Doses over these amounts might increase the risk of neonatal hypocalcemia-induced seizures possibly caused by transient neonatal hypoparathyroidism in the setting of excessive calcium supplementation during pregnancy, especially during the third trimester. Neonatal hypocalcemia is a risk factor for neonatal seizures (97345).

(Read more about CALCIUM)

LIKELY SAFE ...when used orally in amounts commonly found in foods (104531,104532).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts, short-term. Chia has been used safely at doses up to 40 grams daily for up to 6 months (16124,97940). ...when used topically, short-term. A product containing chia seed oil 4% has been applied to the skin safely for up to 8 weeks (25537).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about CHIA)

LIKELY SAFE ...when used orally and appropriately, short-term. Tablets and liquids containing chlorella 3-10 grams or 60-100 mL daily have been safely used in clinical studies lasting 2-3 months (5890,92130,92131). Also, chlorella extract 200-1800 mg daily has been safely used in clinical research for 4-6 weeks (10388,92132). There is insufficient reliable information available about the safety of chlorella when used topically.

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately in medicinal amounts for up to approximately 28 weeks. A commercially available chlorella supplement (Sun Chlorella A, Sun Chlorella Corp.) has been safely used in doses of 6 grams daily, starting during the 12-18th week of gestation and continuing until delivery (95013).

LACTATION:
Insufficient reliable information available; avoid using.

(Read more about CHLORELLA)

LIKELY SAFE ...when used orally as food (11358,11359). Glucomannan powder or flour is often used to enrich noodles in traditional Japanese foods.

POSSIBLY SAFE ...when used orally with at least 250 mL (8 ounces) of water or other fluid. Glucomannan has been safely used in studies lasting up to 4 months (178,179,181,182,11046,11294,11357,11294,54240,57775)(57781,57783,57784,92004,92008,92009,92010,92011,106410). In the European Union, the maximum permitted level in foods is 10 grams/kg (106411).

POSSIBLY UNSAFE ...when used orally without any liquid, especially when in tablet form. There have been reports of choking and esophageal or gastrointestinal obstruction when glucomannan products are taken dry. A safety alert for this has been issued by Health Canada (11293,57785,106410).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately with at least 250 mL (8 ounces) of water or other fluid. Glucomannan has been safely used in children for up to 4 months (179,180,11295,57775,57779,92005,92006,97935).

CHILDREN: LIKELY UNSAFE
when used orally without any liquid, especially when in tablet form. There have been reports of esophageal and gastrointestinal obstruction when glucomannan products are taken dry (11293,57785,106410).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about GLUCOMANNAN)

LIKELY SAFE ...when used orally and appropriately. For people age 14 and older with adequate iron stores, iron supplements are safe when used in doses below the tolerable upper intake level (UL) of 45 mg per day of elemental iron. The UL is not meant to apply to those who receive iron under medical supervision (7135,96621). To treat iron deficiency, most people can safely take up to 300 mg elemental iron per day (15). ...when used intravenously and appropriately. Ferric carboxymaltose 200 mg and iron sucrose 200 mg have been given intravenously for up to 10 doses with no reported serious adverse effects (91179). A meta-analysis of clinical studies of hemodialysis patients shows that administering high-dose intravenous (IV) iron does not increase the risk of hospitalization, infection, cardiovascular events, or death when compared with low-dose IV iron, oral iron, or no iron treatment (102861). A more recent meta-analysis of clinical studies of all patient populations shows that administering IV iron does not increase the risk of hospital length of stay or mortality, although the risk of infection is increased by 16% when compared with oral iron or no iron (110186). Despite these findings, there are rare reports of hypophosphatemia and/or osteomalacia (112603,112608,112609,112610).

LIKELY UNSAFE ...when used orally in excessive doses. Doses of 30 mg/kg are associated with acute toxicity. Long-term use of high doses of iron can cause hemosiderosis and multiple organ damage. The estimated lethal dose of iron is 180-300 mg/kg; however, doses as low as 60 mg/kg have also been lethal (15).

CHILDREN: LIKELY SAFE
when used orally and appropriately (7135,91183,112601).

CHILDREN: LIKELY UNSAFE
when used orally in excessive amounts. Tell patients who are not iron-deficient not to use doses above the tolerable upper intake level (UL) of 40 mg per day of elemental iron for infants and children. Higher doses frequently cause gastrointestinal side effects such as constipation and nausea (7135,20097). Iron is the most common cause of pediatric poisoning deaths. Doses as low as 60 mg/kg can be fatal (15).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Iron is safe during pregnancy and breast-feeding in patients with adequate iron stores when used in doses below the tolerable upper intake level (UL) of 45 mg daily of elemental iron (7135,96625,110180).

PREGNANCY AND LACTATION: LIKELY UNSAFE
when used orally in high doses. Tell patients who are not iron deficient to avoid exceeding the tolerable upper intake level (UL) of 45 mg daily of elemental iron. Higher doses frequently cause gastrointestinal side effects such as nausea and vomiting (7135) and might increase the risk of preterm labor (100969). High hemoglobin concentrations at the time of delivery are associated with adverse pregnancy outcomes (7135,20109).

(Read more about IRON)

LIKELY SAFE ...when used orally in food amounts. Pea protein is commonly consumed as a food (94935,94970,94981).

POSSIBLY SAFE ...when pea protein is used orally in medicinal amounts, short term. Pea protein has been used with apparent safety in doses of up to 50 grams daily for up to 12 weeks (95426,94934,102013,104758,104759). ...when pea protein hydrolysate is used orally, short term. A pea protein hydrolysate has been used with apparent safety at doses of up to 3 grams daily for up to 3 weeks (94973).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using in amounts greater than those found in food.

(Read more about PEA PROTEIN)

LIKELY SAFE ...when used orally in doses up to 100 mEq total potassium daily, not to exceed 200 mEq in a 24-hour period (95010,107989). Oral potassium chloride and potassium citrate are FDA-approved prescription products (95010,107989). Larger doses increase the risk of hyperkalemia (15). ...when administered intravenously (IV) at appropriate infusion rates (95011). Parenteral potassium is an FDA-approved prescription product (15,95011). A tolerable upper intake level (UL) for potassium has not been established; however, potassium levels should be monitored in individuals at increased risk for hyperkalemia, such as those with kidney disease, heart failure, and adrenal insufficiency (100310,107966).

CHILDREN: LIKELY SAFE
when used orally and appropriately in dietary amounts. A tolerable upper intake level (UL) has not been established for healthy individuals (6243,100310).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in dietary amounts of 40-80 mEq daily (15). A tolerable upper intake level (UL) has not been established for healthy individuals (100310).

(Read more about POTASSIUM)

LIKELY SAFE ...when used orally and appropriately in amounts commonly found in foods.

POSSIBLY SAFE ...when the seed or seed oil is used orally and appropriately in medicinal amounts, short-term. Pumpkin seed has been used with apparent safety in a dose of up to 10 grams daily for up to 12 months (92383). Pumpkin seed oil has been used with apparent safety in a dose of up to 400 mg daily for up to 6 months (92378). There is insufficient reliable information available about the safety of pumpkin seed oil when used topically.

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using amounts greater than those found in food.

(Read more about PUMPKIN)

LIKELY SAFE ...when used orally and appropriately. Sodium is safe in amounts that do not exceed the Chronic Disease Risk Reduction (CDRR) intake level of 2.3 grams daily (100310). Higher doses can be safely used therapeutically with appropriate medical monitoring (26226,26227).

POSSIBLY UNSAFE ...when used orally in high doses. Tell patients to avoid exceeding the CDRR intake level of 2.3 grams daily (100310). Higher intake can cause hypertension and increase the risk of cardiovascular disease (26229,98176,98177,98178,98181,98183,98184,100310,109395,109396,109398,109399). There is insufficient reliable information available about the safety of sodium when used topically.

CHILDREN: LIKELY SAFE
when used orally and appropriately (26229,100310). Sodium is safe in amounts that do not exceed the CDRR intake level of 1.2 grams daily for children 1 to 3 years, 1.5 grams daily for children 4 to 8 years, 1.8 grams daily for children 9 to 13 years, and 2.3 grams daily for adolescents (100310).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Tell patients to avoid prolonged use of doses exceeding the CDRR intake level of 1.2 grams daily for children 1 to 3 years, 1.5 grams daily for children 4 to 8 years, 1.8 grams daily for children 9 to 13 years, and 2.3 grams daily for adolescents (100310). Higher intake can cause hypertension (26229).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Sodium is safe in amounts that do not exceed the CDRR intake level of 2.3 grams daily (100310).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in higher doses. Higher intake can cause hypertension (100310). Also, both the highest and the lowest pre-pregnancy sodium quintile intakes are associated with an increased risk of hypertensive disorders of pregnancy, including gestational hypertension and pre-eclampsia, and the delivery of small for gestational age (SGA) infants when compared to the middle intake quintile (106264).

(Read more about SODIUM)

LIKELY SAFE ...when used orally or intramuscularly and appropriately. Vitamin A, as pre-formed vitamin A (retinol or retinyl ester), is safe in adults when taken in doses below the tolerable upper intake level (UL) of 10,000 IU (3000 mcg) per day (7135). Higher doses increase the risk of side effects. There is also growing concern that taking high doses of antioxidants such as vitamin A might do more harm than good. In an analysis of studies, taking vitamin A supplements alone or in combination with other antioxidants is associated with an increased risk of mortality from all causes (15305,90775). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

POSSIBLY SAFE ...when used topically and appropriately, short-term. Retinol 0.5% has been used on the skin daily for up to 12 weeks with apparent safety. No serious adverse effects have been reported in clinical trials (103671,103680).

POSSIBLY UNSAFE ...when used orally in high doses. Doses higher than the UL of 10,000 IU (3000 mcg) per day of pre-formed vitamin A (retinol or retinyl ester) might increase the risk of side effects (7135). While vitamin A 25,000 IU (as retinyl palmitate) daily for 6 months followed by 10,000 IU daily for 6 months has been used with apparent safety in one clinical trial (95052), prolonged use of excessive doses of vitamin A can cause significant side effects such as hypervitaminosis A. The risk for developing hypervitaminosis A is related to total cumulative dose of vitamin A rather than a specific daily dose (1467,1469). There is also concern that taking high doses of antioxidants such as vitamin A might do more harm than good. In an analysis of studies, taking vitamin A supplements alone or in combination with other antioxidants is associated with an increased risk of mortality from all causes (15305,90775). There is insufficient reliable information available about the safety of using sublingual formulations of vitamin A.

CHILDREN: LIKELY SAFE
when used orally or intramuscularly and appropriately. The amount of pre-formed vitamin A (retinol or retinyl ester) that is safe depends on age. For children up to 3 years of age, doses less than 2000 IU (600 mcg) per day seem to be safe. For children ages 4 to 8, doses less than 3000 IU (900 mcg) per day seem to be safe. For children ages 9 to 13, doses less than 5667 IU (1700 mcg) per day seem to be safe. For children 14 to 18, doses less than 9333 IU (2800 mcg) per day seem to be safe (7135). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

CHILDREN: POSSIBLY UNSAFE
when pre-formed vitamin A (retinol or retinyl ester) is used orally in excessive doses. For children up to 3 years of age, avoid doses greater than 2000 IU (600 mcg) per day. For children ages 4 to 8, avoid doses greater than 3000 IU (900 mcg) per day. For children ages 9 to 13, avoid doses greater than 5667 IU (1700 mcg) per day. For children ages 14 to 18, avoid doses greater than 9333 IU (2800 mcg) per day (7135). Higher doses of vitamin A supplementation have been associated with increased risk of side effects such as pneumonia, bone pain, and diarrhea (319,95051). Long-term supplementation with low to moderate doses on a regular basis can cause severe, but usually reversible, liver damage (11978).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally or intramuscularly and appropriately. Vitamin A, as pre-formed vitamin A (retinol or retinyl ester), is safe during pregnancy and lactation when used in doses less than 10,000 IU (3000 mcg) per day (7135,16823,107293). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally or intramuscularly in excessive doses. Daily intake of greater than 10,000 IU (3000 mcg) can cause fetal malformations (3066,7135). Excessive dietary intake of vitamin A has also been associated with teratogenicity (11978). The first trimester of pregnancy seems to be the critical period for susceptibility to vitamin A-associated birth defects such as craniofacial abnormalities and abnormalities of the central nervous system (7135). Pregnant patients should monitor their intake of pre-formed vitamin A (retinol or retinyl ester). This form of vitamin A is found in several foods including animal products, some fortified breakfast cereals, and dietary supplements (3066).

(Read more about VITAMIN A)

LIKELY SAFE ...when used orally, topically, intramuscularly, or intravenously and appropriately. Vitamin C is safe when taken orally in doses below the tolerable upper intake level (UL). Tell patients not to exceed the UL of 2000 mg daily (1959,4713,4714,4844). ...when used intravenously or intramuscularly and appropriately. Injectable vitamin C is an FDA-approved prescription product (15).

POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 2000 mg daily can significantly increase the risk of adverse effects such as osmotic diarrhea and gastrointestinal upset (4844).

CHILDREN: LIKELY SAFE
when used orally and appropriately (4844,10352,14443).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 400 mg daily for children ages 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years. Higher doses can cause osmotic diarrhea and gastrointestinal upset (4844).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (4844).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Tell patients over age 19 not to use doses exceeding the UL of 2000 mg daily when pregnant or breast-feeding and for those 14-18 years of age not to use doses exceeding 1800 mg daily when pregnant or breast-feeding. Higher doses can cause osmotic diarrhea and gastrointestinal upset. Large doses of vitamin C during pregnancy can also cause newborn scurvy (4844); avoid using.

(Read more about VITAMIN C)

LIKELY SAFE ...when consumed in amounts found in foods, up to 10 mg/kg per day (4914). It has Generally Recognized as Safe (GRAS) status in the US (4912). ...when used orally for medicinal use in amounts up to 15 grams per day (4914,4916,4917,4918). ...when used topically and appropriately (4914,89591,95794).

PREGNANCY AND LACTATION:
Insufficient reliable information is available; avoid using in amounts greater than those found in foods.

(Read more about XANTHAN GUM)

(Read more about ALGIN)

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, spirulina blue-green algae might increase the risk of bleeding if used with other anticoagulant or antiplatelet drugs. However, this is unlikely.  Details Spirulina blue-green algae have shown antiplatelet and anticoagulant effects in vitro (18311,18312,75892,92162,92163). However, one preliminary study in 24 patients receiving spirulina blue-green algae 2.3 grams daily for 2 weeks showed no effect on platelet activation or measures of clotting time (97202).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking blue-green algae with antidiabetes drugs might increase the risk of hypoglycemia.  Details Human research shows that spirulina blue-green algae can have hypoglycemic effects in patients with diabetes, at least some of whom were using antidiabetes drugs (18299). However, blue-green algae does not seem to improve glycated hemoglobin (HbA1c) levels in patients with diabetes (102689,109970). A meta-analysis of animal studies also suggests that spirulina blue-green algae have hypoglycemic effects (109970).

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, concurrent use of blue-green algae might interfere with immunosuppressive therapy.  Details Blue-green algae have been shown to stimulate the immune system (2534,10267).

(Read more about BLUE-GREEN ALGAE)

(Read more about BROWN RICE)

ALUMINUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Calcium citrate might increase aluminum absorption and toxicity. Other types of calcium do not increase aluminum absorption.  Details Calcium citrate can increase the absorption of aluminum when taken with aluminum hydroxide. The increase in aluminum levels may become toxic, particularly in individuals with kidney disease (21631). However, the effect of calcium citrate on aluminum absorption is due to the citrate anion rather than calcium cation. Calcium acetate does not appear to increase aluminum absorption (93006).

BISPHOSPHONATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Calcium reduces the absorption of bisphosphonates.  Details Advise patients to take bisphosphonates at least 30 minutes before calcium, but preferably at a different time of day. Calcium supplements decrease absorption of bisphosphonates (12937).

CALCIPOTRIENE (Dovonex) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Taking calcipotriene with calcium might increase the risk for hypercalcemia.  Details Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia (12938). Theoretically, combining calcipotriene with calcium supplements might increase the risk of hypercalcemia.

CALCIUM CHANNEL BLOCKERS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Intravenous calcium may decrease the effects of calcium channel blockers; oral calcium is unlikely to have this effect.  Details Intravenous calcium is used to decrease the effects of calcium channel blockers in the management of overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects (6124). But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers (12939,12947).

CEFTRIAXONE (Rocephin) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Co-administration of intravenous calcium and ceftriaxone can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys.  Details Avoid administering intravenous calcium in any form, such as parenteral nutrition or Lactated Ringers, within 48 hours of intravenous ceftriaxone. Case reports in neonates show that administering intravenous ceftriaxone and calcium can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys. In several cases, neonates have died as a result of this interaction (15794,21632). So far there are no reports in adults; however, there is still concern that this interaction might occur in adults.

DIGOXIN (Lanoxin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Using intravenous calcium with digoxin might increase the risk of fatal cardiac arrhythmias.  Details Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin (12940). However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin (38960).

DILTIAZEM (Cardizem, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, calcium may reduce the therapeutic effects of diltiazem.  Details Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, calcium might increase this risk of hypercalcemia and reduce the effectiveness of diltiazem.

DOLUTEGRAVIR (Tivicay) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce levels of dolutegravir.  Details Advise patients to take dolutegravir either 2 hours before or 6 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium carbonate 1200 mg concomitantly with dolutegravir 50 mg reduces plasma levels of dolutegravir by almost 40%. Calcium appears to decrease levels of dolutegravir through chelation (93578).

ELVITEGRAVIR (Vitekta) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce levels of elvitegravir.  Details Advise patients to take elvitegravir either 2 hours before or 2 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium along with elvitegravir can reduce blood levels of elvitegravir through chelation (94166).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce the absorption and effectiveness of levothyroxine.  Details Advise patients to take levothyroxine and calcium supplements at least 4 hours apart. Calcium reduces levothyroxine absorption, probably by forming insoluble complexes (5082). Calcium carbonate supplements reduce effectiveness of levothyroxine in patients with hypothyroidism (5081,5082,6137).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, concomitant use of calcium and lithium may increase this risk of hypercalcemia.  Details Clinical research suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients (38953). Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

QUINOLONE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce the absorption of quinolone antibiotics.  Details Advise patients to take oral quinolones at least 2 hours before or 4-6 hours after calcium supplements or calcium-fortified foods. Taking calcium at the same time as oral quinolones can reduce quinolone absorption. Calcium binds to quinolones in the gut (4412,10339,21638,38570).

RALTEGRAVIR (Isentress) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Calcium may reduce levels of raltegravir.  Details Pharmacokinetic research shows that taking a single dose of calcium carbonate 3000 mg along with raltegravir 400 mg twice daily modestly decreases the mean area under the curve of raltegravir, but the decrease does not necessitate a dose adjustment of raltegravir (94164). However, a case of elevated HIV-1 RNA levels and documented resistance to raltegravir has been reported for a patient taking calcium carbonate 1 gram three times daily plus vitamin D3 (cholecalciferol) 400 IU three times daily in combination with raltegravir 400 mg twice daily for 11 months. It is thought that calcium reduced raltegravir levels by chelation, leading to treatment failure (94165).

SOTALOL (Betapace) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Calcium seems to reduce the absorption of sotalol.  Details Advise patients to separate doses by at least 2 hours before or 4-6 hours after calcium. Calcium appears to reduce the absorption of sotalol, probably by forming insoluble complexes (10018).

TETRACYCLINE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Calcium seems to reduce the absorption of tetracycline antibiotics.  Details Advise patients to take oral tetracyclines at least 2 hours before, or 4-6 hours after calcium supplements. Taking calcium at the same time as oral tetracyclines can reduce tetracycline absorption. Calcium binds to tetracyclines in the gut (1843).

THIAZIDE DIURETICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Taking calcium along with thiazides might increase the risk of hypercalcemia and renal failure.  Details Thiazides reduce calcium excretion by the kidneys (1902). Using thiazides along with moderately large amounts of calcium carbonate increases the risk of milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure). Patients may need to have their serum calcium levels and/or parathyroid function monitored regularly.

VERAPAMIL (Calan, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, calcium may reduce the therapeutic effects of verapamil.  Details Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, use of calcium supplements may increase this risk of hypercalcemia and reduce the effectiveness of verapamil.

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PHOTOSENSITIZING DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, chlorella might have additive effects with photosensitizing drugs.  Details Chlorella has been reported to cause photosensitization (3900,5852). In five case reports, patients who had ingested chlorella exhibited swelling followed by erythematopurpuric lesions on sun-exposed areas of the body (5852). Theoretically, concomitant use with photosensitizing drugs may exacerbate effects.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, chlorella might reduce the clinical effects of warfarin.  Details Chlorella contains significant amounts of vitamin K. There is at least one case report of warfarin therapy becoming sub-therapeutic after initiation of chlorella supplements (3900,41830).

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ORAL DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, glucomannan may decrease absorption of drugs taken orally.  Details Due to its viscosity and bulking effects, there is concern that glucomannan can decrease the absorption of oral drugs. A small clinical study in healthy volunteers shows that taking glyburide 2.5 mg plus glucomannan 3.9 grams with breakfast reduces plasma levels of glyburide when compared with breakfast and glyburide alone (11360). In addition, animal research demonstrates this effect on amoxicillin, but shows increased absorption of metronidazole. This mouse model also demonstrates that metronidazole elimination is prolonged, but amoxicillin elimination is enhanced by 38%; glucomannan may also affect the distribution of some drugs (112703). To avoid changes in absorption, take glucomannan 30-60 minutes after taking oral drugs.

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BISPHOSPHONATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Iron reduces the absorption of bisphosphonates.  Details Advise patients that doses of bisphosphonates should be separated by at least two hours from doses of all other medications, including supplements such as iron. Divalent cations, including iron, can decrease absorption of bisphosphonates by forming insoluble complexes in the gastrointestinal tract (15).

CHLORAMPHENICOL Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, taking chloramphenicol with iron might reduce the response to iron therapy in iron deficiency anemia.  Details Chloramphenicol interferes with erythrocyte maturation (15,3046). However, since chloramphenicol isn't usually taken for prolonged periods, this isn't likely to be clinically significant.

DOLUTEGRAVIR (Tivicay) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Iron might decrease dolutegravir levels by reducing its absorption.  Details Advise patients to take dolutegravir at least 2 hours before or 6 hours after taking iron. Pharmacokinetic research shows that iron can decrease the absorption of dolutegravir from the gastrointestinal tract through chelation (93578). When taken under fasting conditions, a single dose of ferrous fumarate 324 mg orally along with dolutegravir 50 mg reduces overall exposure to dolutegravir by 54% (94190).

INTEGRASE INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking iron along with integrase inhibitors might decrease the levels and clinical effects of these drugs.  Details Iron is a divalent cation. There is concern that iron may decrease the absorption of integrase inhibitors from the gastrointestinal tract through chelation (93578). One pharmacokinetic study shows that iron can decrease blood levels of the specific integrase inhibitor dolutegravir through chelation (94190). Also, other pharmacokinetic research shows that other divalent cations such as calcium can decrease the absorption and levels of some integrase inhibitors through chelation (93578,93579).

LEVODOPA Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Iron might decrease levodopa levels by reducing its absorption.  Details Advise patients to separate doses of levodopa and iron as much as possible. There is some evidence in healthy people that iron forms chelates with levodopa, reducing the amount of levodopa absorbed by around 50% (9567). The clinical significance of this hasn't been determined.

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Iron might decrease levothyroxine levels by reducing its absorption.  Details Advise patients to separate levothyroxine and iron doses by at least 2 hours. Iron can decrease the absorption and efficacy of levothyroxine by forming insoluble complexes in the gastrointestinal tract (9568).

METHYLDOPA (Aldomet) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Iron might decrease methyldopa levels by reducing its absorption.  Details Advise patients to separate methyldopa and iron doses by at least 2 hours. Iron can decrease the absorption of methyldopa from the gastrointestinal tract through chelation, resulting in increases in blood pressure (7900,20151).

MYCOPHENOLATE MOFETIL (CellCept) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, iron might decrease mycophenolate mofetil levels by reducing its absorption.  Details Advise patients to take iron 4-6 hours before, or 2 hours after, mycophenolate mofetil. It has been suggested that a decrease of absorption is possible, probably by forming nonabsorbable chelates. However, mycophenolate pharmacokinetics are not affected by iron supplementation in available clinical research (3046,20152,20153,20154,20155).

PENICILLAMINE (Cuprimine, Depen) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Iron might decrease penicillamine levels by reducing its absorption.  Details Advise patients to separate penicillamine and iron doses by at least 2 hours. Oral iron supplements can reduce absorption of penicillamine by 30% to 70%, probably due to chelate formation. In people with Wilson's disease, this interaction has led to reduced efficacy of penicillamine (3046,3072,20156).

QUINOLONE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Iron might decrease levels of quinolone antibiotics by reducing their absorption.  Details Advise patients to separate quinolone antibiotics and iron doses by at least 2 hours. Iron decreases the absorption of quinolones due to formation of insoluble complexes in the gastrointestinal tract (15,3072).

TETRACYCLINE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Iron might decrease levels of tetracycline antibiotics by reducing their absorption.  Details Advise patients to take iron at least 2 hours before or 4 hours after tetracycline antibiotics. Concomitant use can decrease absorption of tetracycline antibiotics from the gastrointestinal tract by 50% to 90% (15).

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ACE INHIBITORS (ACEIs) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Likely •  Level of Evidence = C Using ACEIs with high doses of potassium increases the risk of hyperkalemia.  Details ACEIs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion (95628). Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia (15,23207). However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels (95628).

ANGIOTENSIN RECEPTOR BLOCKERS (ARBs) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Likely •  Level of Evidence = C Using ARBs with high doses of potassium increases the risk of hyperkalemia.  Details ARBs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion (95628). Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia (15,23207). However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels (95628).

POTASSIUM-SPARING DIURETICS Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Likely •  Level of Evidence = C Concomitant use increases the risk of hyperkalemia.  Details Using potassium-sparing diuretics with potassium supplements increases the risk of hyperkalemia (15).

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LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Pumpkin might reduce excretion and increase levels of lithium.  Details Pumpkin is thought to have diuretic properties (92383). Theoretically, this might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.

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ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = A Theoretically, a high intake of dietary sodium might reduce the effectiveness of antihypertensive drugs.  Details High intake of dietary sodium can increase systolic and diastolic blood pressure (26222). Also, high intake of sodium may necessitate increased use of antihypertensive medications to achieve blood pressure control in some patients, such as those with chronic kidney disease (26223).

CORTICOSTEROIDS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Concomitant use of mineralocorticoids and some glucocorticoids with sodium supplements might increase the risk of hypernatremia.  Details Mineralocorticoids and some glucocorticoids (corticosteroids) cause sodium retention. This effect is dose-related and depends on mineralocorticoid potency. It is most common with hydrocortisone, cortisone, and fludrocortisone, followed by prednisone and prednisolone (4425).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Altering dietary intake of sodium might alter the levels and clinical effects of lithium.  Details High sodium intake can reduce plasma concentrations of lithium by increasing lithium excretion (26225). Reducing sodium intake can significantly increase plasma concentrations of lithium and cause lithium toxicity in patients being treated with lithium carbonate (26224,26225). Stabilizing sodium intake is shown to reduce the percentage of patients with lithium level fluctuations above 0.8 mEq/L (112909). Patients taking lithium should avoid significant alterations in their dietary intake of sodium.

SODIUM-CONTAINING DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Concomitant use of sodium-containing drugs with additional sodium from dietary or supplemental sources may increase the risk of hypernatremia and long-term sodium-related complications.  Details The Chronic Disease Risk Reduction (CDRR) intake level of 2.3 grams of sodium daily indicates the intake at which it is believed that chronic disease risk increases for the apparently healthy population (100310). Some medications contain high quantities of sodium. When used in conjunction with sodium supplements or high-sodium diets, the CDRR may be exceeded. Additionally, concomitant use may increase the risk for hypernatremia; this risk is highest in the elderly and people with other risk factors for electrolyte disturbances.

TOLVAPTAN (Samsca) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, concomitant use of tolvaptan with sodium might increase the risk of hypernatremia.  Details Tolvaptan is a vasopressin receptor 2 antagonist that is used to increase sodium levels in patients with hyponatremia (29406). Patients taking tolvaptan should use caution with the use of sodium salts such as sodium chloride.

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HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = C Theoretically, taking high doses of vitamin A in combination with other potentially hepatotoxic drugs might increase the risk of liver disease.  Details The tolerable upper intake level (UL) is the highest level of intake that is likely to pose no risk of adverse effects. Doses of vitamin A above the UL can cause hepatotoxicity, ranging from elevated liver enzymes to liver failure (7135,82554).

RETINOIDS Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Concomitant use of retinoids with vitamin A supplements might produce supratherapeutic vitamin A levels.  Details Retinoids, which are vitamin A derivatives, could have additive toxic effects when taken with vitamin A supplements (3046).

TETRACYCLINE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking tetracycline antibiotics with high doses of vitamin A can increase the risk of pseudotumor cerebri.  Details Benign intracranial hypertension (pseudotumor cerebri) can occur with tetracyclines and with acute or chronic vitamin A toxicity. Case reports suggest that taking tetracyclines and vitamin A concurrently can increase the risk of this condition (10545,10546,10547). Avoid high doses of vitamin A in people taking tetracyclines chronically.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, high doses of vitamin A could increase the risk of bleeding with warfarin.  Details Vitamin A toxicity is associated with hemorrhage and hypoprothrombinemia, possibly due to vitamin K antagonism (505). Advise patients taking warfarin to avoid doses of vitamin A above the tolerable upper intake level of 10,000 IU/day for adults.

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ACETAMINOPHEN (Tylenol, others) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Probable •  Level of Evidence = B High-dose vitamin C might slightly prolong the clearance of acetaminophen.  Details A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases (6451). This effect is not likely to be clinically significant.

ALKYLATING AGENTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

ALUMINUM Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.  Details Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption (10549,10550,10551,21556). In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely (10549). Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

ANTITUMOR ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

ASPIRIN Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase aspirin levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction is not clinically significant.

CHOLINE MAGNESIUM TRISALICYLATE (Trilisate) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046,4531). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C might increase blood levels of estrogens.  Details Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products (129,130,11161). It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall (129,11161). When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements (11161). Monitor these patients for estrogen-related side effects.

FLUPHENAZINE (Prolixin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, vitamin C might decrease levels of fluphenazine.  Details In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started (11017). The mechanism is not known, and there is no further data to confirm this interaction.

INDINAVIR (Crixivan) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can modestly reduce indinavir levels.  Details One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown (11300,93578).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase levothyroxine absorption.  Details Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH (102978).

NIACIN Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = A Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.  Details A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

SALSALATE (Disalcid) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase salsalate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D High-dose vitamin C might reduce the levels and effectiveness of warfarin.  Details Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption (11566). There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time (9804,9806). Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant (9805,9806,11566,11567). However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR) (90942). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

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(Read more about XANTHAN GUM)

General ...Orally, algin is well tolerated in amounts typically found in foods (11). No adverse effects related to medicinal amounts of algin have been reported. However, a thorough evaluation of safety outcomes has not been conducted.

(Read more about ALGIN)

General ...Orally, spirulina blue-green algae seem to be well tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, bloating, diarrhea, dizziness, fatigue, flatulence, headache, nausea, and vomiting.

Dermatologic ...Orally, a severe rash has been reported in a 49-year-old woman after taking a spirulina blue-green algae supplement (species and dose unknown). After stopping the supplement, inflammatory myopathy with muscle weakness and elevated creatine kinase occurred. The condition resolved with corticosteroid and cyclophosphamide treatment (75936). In another case report, an 82 year-old woman developed a blistering skin condition over a 2-year period while taking spirulina blue-green algae (A. platensis, dose unknown). She had partly hemorrhagic bullae, secreting erosions and macerations. These symptoms resolved when the supplement was stopped and the patient was treated with oral prednisone, topical silver sulfadiazine, and topical triamcinolone / neomycin (75921).

Gastrointestinal ...Orally, gastrointestinal complaints are amongst the most common adverse effects associated with spirulina blue-green algae, including nausea, vomiting, diarrhea, and abdominal cramps (19272,75924,91713,109969). Similarly, common adverse effects associated with the blue-green algae species Aphanizomenon flos-aquae are stomach upset, flatulence, diarrhea, and bloating (14842).

Hematologic ...Orally, three cases of mild gum bleeding and one case of mild bruising have been reported in patients taking spirulina blue-green algae (Cyactiv, Cerule LLC) 2. 3 grams daily (containing approximately 1 gram of phycocanin) for 2 weeks (97202).

Hepatic ...Orally, significant elevations of liver function tests within 2 weeks of starting a spirulina blue-green algae supplement (species and dose unknown) have been reported in a 52-year-old man stabilized on amlodipine, simvastatin, and acarbose. A biopsy showed feathery degeneration and ballooning of hepatic cells. Cholestasis was present, and an ex-vivo lymphocyte stimulation test for spirulina blue-green algae was positive. All drugs and the spirulina blue-green algae supplement were stopped, with return of the LFTs to normal (9172).

Immunologic ...Orally, urticarial rashes and pruritus have occurred as part of generalized allergic reactions to blue-green algae (91706,91711,91712).
In one case report, a 14-year-old male experienced anaphylaxis with urticaria, lip edema, and asthma 6 hours after taking five tablets of spirulina blue-green algae (A. platensis, strength unknown). He had a positive skin prick test. Oral challenge to an extract of the tablets, and IgE from his serum, reacted with the beta chain of C-phycocyanin from A. platensis (91712).
In another case report, a 17-year-old male with a history of multiple allergies developed rash, pruritus, angioedema, wheezing, and dyspnea within 10 minutes of taking spirulina blue-green algae (A. platensis) 300 mg. He had a positive skin test to A. platensis but no other ingredients of the tablets (91706).

Musculoskeletal ...Orally, after a 49-year-old woman stopped taking a spirulina blue-green algae supplement (species and dose unknown), the patient experienced inflammatory myopathy with muscle weakness and elevated creatine kinase. The condition resolved with corticosteroid and cyclophosphamide treatment (75936). Another case report describes acute rhabdomyolysis that occurred after consumption of spirulina (Arthrospira platensis, Hawaiian spirulina, Solgar Inc., Leonia, NJ) 3 grams daily for 1 month. The 24-year old man presented with weakness, myalgias, elevated creatine kinase and liver function tests, and myoglobinuria (75922).

(Read more about BLUE-GREEN ALGAE)

General ...Orally, brown rice is well tolerated when consumed as a food. No adverse effects have been reported when used in medicinal amounts; however, a thorough evaluation of safety outcomes has not been conducted.

(Read more about BROWN RICE)

General ...Orally and intravenously, calcium is well-tolerated when used appropriately.
Most Common Adverse Effects:
Orally: Belching, constipation, diarrhea, flatulence, and stomach upset.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about calciphylaxis and kidney stones.

Cardiovascular ...There has been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these results, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Reasons for these discrepancies are not entirely clear. It may relate to whether calcium is taken as monotherapy or in combination with vitamin D. When taken with vitamin D, which is commonly recommended, calcium supplementation does not appear to be associated with an increased risk of CVD, CHD, or MI (93533,107231). Also, the association between calcium supplementation and CVD, CHD, or MI risk may be influenced by the amount of calcium consumed as part of the diet. Supplementation with calcium may be associated with an increased risk of MI in people with dietary calcium intake above 805 mg daily, but not in those with dietary calcium intake below 805 mg daily (17482). To minimize the possible risk of CVD, CHD, or MI, advise patients not to consume more than the recommended daily intake of 1000-1200 mg and to consider total calcium intake from both dietary and supplemental sources (17484). While dietary intake of calcium is preferred over supplemental intake, advise patients who require calcium supplements to take calcium along with vitamin D, as this combination does not appear to be associated with an increased risk of MI (93533).
Rarely, calcium intake can increase the risk of calciphylaxis, which usually occurs in patients with kidney failure. Calciphylaxis is the deposition of calcium phosphate in arterioles, which causes skin ulcers and skin necrosis. In a case report, a 64-year-old female with a history of neck fracture, sepsis, and ischemic colitis presented with painful leg ulcers due to calciphylaxis. She discontinued calcium and vitamin D supplementation and was treated with sodium thiosulfate and supportive care (95816).

Gastrointestinal ...Orally, calcium can cause belching, flatulence, nausea, gastrointestinal discomfort, and diarrhea (1824,1843,12950,38803). Although constipation is frequently cited as an adverse effect of calcium, there is no scientific substantiation of this side effect (1824,1843,1844,1845,12950,38978). Calcium carbonate has been reported to cause acid rebound, but this is controversial (12935,12936).

Oncologic ...There is some concern that very high doses of calcium might increase the risk of prostate cancer. Some epidemiological evidence suggests that consuming over 2000 mg/day of dietary calcium might increase the risk for prostate cancer (4825,12949). Additional research suggests that calcium intake over 1500 mg/day might increase the risk of advanced prostate cancer and prostate cancer mortality (14132). Consumption of dairy products has also been weakly linked to a small increase in prostate cancer risk (98894). However, contradictory research suggests no association between dietary intake of calcium and overall prostate cancer risk (14131,14132,104630). More evidence is needed to determine the effect of calcium, if any, on prostate cancer risk.

Renal ...Kidney stones have been reported in individuals taking calcium carbonate 1500 mg daily in combination with vitamin D 2000 IU daily for 4 years (93943).

(Read more about CALCIUM)

General ...Orally and topically, chia seems to be well tolerated.
Most Common Adverse Effects:
Orally: Flatulence and soft stools.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis in sensitive individuals.

Cardiovascular ...Chia contains a high concentration of alpha-linolenic acid (ALA). There is some concern that ALA might increase triglyceride levels more than other omega-3 fatty acids (12918); however, clinical research with a specific variety of chia called Salba shows that it does not significantly increase triglyceride levels (16124).

Gastrointestinal ...Orally, chia might cause mild gastrointestinal adverse effects. Some patients consuming chia 40 grams daily for up to 6 months reported mild and transient gastrointestinal adverse effects such as flatulence and soft stools; however, the frequency of these adverse effects was similar to patients consuming an oat bran control (97940). Bloating and flatulence have been reported with a chia flour-based sports beverage (112385).

Immunologic ...Orally, chia might cause anaphylaxis in sensitive individuals. A single case of IgE-mediated anaphylactic reaction has been reported for a patient who consumed chia seeds. Symptoms, including pruritus in the mouth, urticaria, facial angioedema, shortness of breath, and dizziness, developed a few days after consuming chia seeds. The reaction was attributed to sensitivity to proteins in chia seeds (91517).

Oncologic ...Chia seeds contain a high concentration of alpha-linolenic acid (ALA). Epidemiologic research suggests that high dietary intake of ALA might increase risk for prostate cancer (1337,2558,7823,7147,12978). Other research suggests high intake or serum levels of ALA does not increase the overall risk of prostate cancer (12961,15736); however, it might increase the risk of advanced prostate cancer (12961). Association with prostate cancer appears to depend on the sources of ALA. Dairy and meat sources have been positively associated with prostate cancer, whereas plant sources, such as chia seed, don't seem to affect prostate cancer risk (12909). According to a clinical trial, intake of ALA does not appear to increase levels of prostate specific antigen (PSA) (91402).

(Read more about CHIA)

General ...Orally, chlorella is generally well-tolerated.
Most Common Adverse Effects:
Orally: Allergic reactions, abdominal cramping, constipation, diarrhea, fatigue, flatus, nausea, photosensitivity, and stool discoloration.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis.

Dermatologic ...Orally, photosensitivity reactions have occurred following ingestion of chlorella (3900,5852). According to case reports, five patients who had ingested chlorella exhibited swelling followed by erythematopurpuric lesions on sun-exposed areas of the body (5852). The photosensitizing agent in the chlorella tablets was identified as pheophorbide-a and its ester.

Gastrointestinal ...Orally, chlorella can cause diarrhea, abdominal cramping, flatus, and nausea, especially during the first two weeks of treatment (5890,6804,92130,92132). In one clinical trial, one out of 42 patients reported nausea and one reported diarrhea (92132). In another trial, taking chlorella tablets (Sun Chlorella A, Sun Chlorella Corp) and a chlorella extract (Wakasa Gold, Sun Chlorella Corp) resulted in transient worsening of constipation in 4 of 13 patients and transient mild diarrhea in 2 of 13 patients (92130).
Green discoloration of the feces has also been reported, due to the chlorophyll content of chlorella (6804,95013).

Hematologic ...Orally, chlorella has been linked to one case of thrombocytopenia; however, causality has not been determined. A 49-year-old female living in Turkey presented with thrombocytopenia (a platelet count of 27,000/mm³) after taking chlorella 1080 mg daily for 20 days. Platelet counts had been normal one month earlier, and returned to normal two weeks after discontinuing the chlorella supplement (99879).

Immunologic ...Allergic reactions, including asthma and anaphylaxis, have been reported in people taking chlorella and in those preparing chlorella tablets (3900,5847,41827,105645).

Neurologic/CNS ...Orally, manganese (Mn)-induced parkinsonism has been reported after long-term consumption of chlorella extract. In this case, a patient on maintenance hemodialysis reported gait disturbance, dysarthria, elevated serum and cerebrospinal fluid manganese levels, and abnormal magnetic resonance imaging (MRI) findings of the brain. The authors identified the condition as a rare case of Mn-induced parkinsonism, which may have been due to long-term ingestion of a chlorella extract containing 1.7 mg of Mn in the usual daily dose. The patient underwent edetic acid infusion therapy, which improved the MRI abnormalities and the other symptoms improved four months later (41817).
In one study, fatigue was reported in 18 of 41 patients receiving chlorella 200 mg (10388).

(Read more about CHLORELLA)

General ...Orally, glucomannan is generally well tolerated when taken with plenty of water or other liquid.
Most Common Adverse Effects:
Orally: Abdominal pain, bloating, constipation, diarrhea, flatulence, nausea, and vomiting.
Serious Adverse Effects (Rare):
Orally: Choking and esophageal or gastrointestinal obstruction, especially when taken as a dry powder or in tablet form.

Gastrointestinal ...Orally, glucomannan can cause gastrointestinal disturbances, including abdominal pain, bloating, constipation, diarrhea, flatulence, nausea, and vomiting, especially when taken in doses of more than 3 grams daily (57781,57784,92004,92010,92011,97935,106411). Esophageal and gastrointestinal obstructions have been reported when dry glucomannan-containing products are taken with insufficient fluid (11293,57785,106410).

Hepatic ...Acute cholestatic hepatitis occurred in a 31-year-old male after taking glucomannan orally for 45 days (57777). He was also taking other supplements, including garlic and chitosan, so it is unclear whether the hepatitis was due to glucomannan, other supplements, or the combination.

Pulmonary/Respiratory ...Cases of occupational respiratory disorders, including respiratory sensitization and bronchial asthma, have been reported in workers exposed to glucomannan (57789,57810).

(Read more about GLUCOMANNAN)

General ...Orally or intravenously, iron is generally well tolerated when used appropriately.
Most Common Adverse Effects:
Orally: Abdominal pain, constipation, diarrhea, gastrointestinal irritation, nausea, and vomiting.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about oral or gastric ulcerations.
Intravenously: Case reports have raised concerns about hypophosphatemia and osteomalacia.

Cardiovascular ...There is debate regarding the association between coronary heart disease (CHD) or myocardial infarction (MI) and high iron intake or high body iron stores. Some observational studies have reported that high body iron stores are associated with increased risk of MI and CHD (1492,9542,9544,9545,15175). Some observational studies reported that only high heme iron intake from dietary sources such as red meat are associated with increased risk of MI and CHD (1492,9546,15174,15205,15206,91180). However, the majority of research has found no association between serum iron levels and cardiovascular disease (1097,1099,9543,9547,9548,9549,9550,56469,56683).
There is one case of Kounis syndrome, also referred to as allergic angina or allergic myocardial infarction, in a 39-year-old female patient without previous coronary artery disease given intravenous ferric carboxymaltose. The patient experienced anaphylactic symptoms, including headache, abdominal pain, and breathing difficulties, 3 minutes after starting the infusion. She was further diagnosed with non-ST-elevation myocardial infarction (112607).

Dermatologic ...Cutaneous hemosiderosis, or skin staining, has been reported following intravenous iron infusion in various case reports. Most of these cases are due to extravasation following iron infusion (112605,112611). In one case, extravasation has occurred following iron derisomaltose infusion in a 41-year-old female with chronic kidney disease (112605). Rarely, diffuse cutaneous hermosiderosis has occurred. In one case, a 31-year-old female with excessive sweating developed cutaneous hemosiderosis in the armpits following an intravenous iron polymaltose infusion (112611).

Endocrine ...Population research in females shows that higher ferritin levels are associated with an approximately 1. 5-fold higher odds of developing gestational diabetes. Increased dietary intake of heme-iron, but not non-heme iron, is also associated with an increased risk for gestational diabetes. The effects of iron supplementation could not be determined from the evaluated research (96618). However, in a sub-analysis of a large clinical trial in pregnant adults, daily supplementation with iron 100 mg from 14 weeks gestation until delivery did not affect the frequency or severity of glucose intolerance or gestational weight gain (96619).

Gastrointestinal ...Orally, iron can cause dry mouth, gastrointestinal irritation, heartburn, abdominal pain, constipation, diarrhea, nausea, or vomiting (96621,102864,104680,104684,110179,110185,110188,110189,110192). These adverse effects are uncommon at doses below the tolerable upper intake level (UL) of 45 mg per day of elemental iron in adults with normal iron stores (7135). Higher doses can be taken safely in adults with iron deficiency, but gastrointestinal side effects may occur (1095,20118,20119,56698,102864). Taking iron supplements with food seems to reduce gastrointestinal side effects (7135). However, food can also significantly reduce iron absorption. Iron should be taken on an empty stomach, unless it cannot be tolerated.
There are several formulations of iron products such as ferrous sulfate, ferrous gluconate, ferrous fumarate, and others. Manufacturers of some formulations, such as polysaccharide-iron complex products (Niferex-150, etc), claim to be better tolerated than other formulations; however, there is no reliable evidence to support this claim. Gastrointestinal tolerability relates mostly to the elemental iron dose rather than the formulation (17500).
Enteric-coated or controlled-release iron formulations might reduce nausea for some patients, however, these products also have lower absorption rates (17500).
Liquid oral preparations can blacken and stain teeth (20118).
Iron can also cause oral ulcerations and ulcerations of the gastric mucosa (56684,91182,96622,110179). In one case report, an 87-year-old female with Alzheimer disease experienced a mucosal ulceration, possibly due to holding a crushed ferrous sulfate 80 mg tablet in the mouth for too long prior to swallowing (91182). The ulceration was resolved after discontinuing iron supplementation. In another case report, a 76-year old male suffered gastric mucosal injury after taking a ferrous sulfate tablet daily for 4 years (56684). In a third case report, a 14-year-old female developed gastritis involving symptoms of upper digestive hemorrhage, nausea, melena, and stomach pain. The hemorrhage was attributed to supplementation with ferrous sulfate 2 hours after meals for the prior 2 weeks (96622). In one case report, a 43-year old female developed atrophic gastritis with non-bleeding ulcerations five days after starting oral ferrous sulfate 325 mg twice daily (110179).
Intravenously, iron can cause gastrointestinal symptoms sch as nausea (104684,110192).

Immunologic ...Although there is some clinical research associating iron supplementation with an increased rate of malaria infection (56796,95432), the strongest evidence to date does not support this association, at least for areas where antimalarial treatment is available (95433,96623). In an analysis of 14 trials, iron supplementation was not associated with an increased risk of malaria (96623). In a sub-analysis of 7 preliminary clinical studies, the effect of iron supplementation was dependent upon the access to services for antimalarial treatment. In areas where anemia is common and services are available, iron supplementation is associated with a 9% reduced risk of clinical malaria. In an area where services are unavailable, iron supplementation was associated with a 16% increased risk in malaria incidence (96623). The difference in these findings is likely associated with the use of malaria prevention methods.
A meta-analysis of clinical studies of all patient populations shows that administering IV iron, usually iron sucrose and ferric carboxymaltose, increases the risk of infection by 16% when compared with oral iron or no iron. However, sub-analyses suggest this increased risk is limited to patients with inflammatory bowel disease (IBD) (110186).
Intravenously, iron has rarely resulted in allergic reactions, including anaphylactoid reactions (110185,110192,112606,112607). There is one case of Kounis syndrome, also referred to as allergic angina or allergic myocardial infarction, in a 39-year-old female patient without previous coronary artery disease given intravenous ferric carboxymaltose. The patient experienced anaphylactic symptoms, including headache, abdominal pain, and breathing difficulties, 3 minutes after starting the infusion. She was further diagnosed with non-ST-elevation myocardial infarction (112607).

Musculoskeletal ...Intravenously, iron rarely results in osteomalacia related to hypophosphatemia (112609). At least 2 cases exist of hypophosphatemic osteomalacia. In one case, a 70-year-old male with a genetic hemorrhagic disorder infused with ferric carboxymaltose developed lower limb pain with hypophosphatemia and diffuse bone demineralization in the feet (112609). In a second case, a 61-year-old male developed femoral neck insufficiency fractures following repeated ferric carboxymaltose transfusions for anemia related to vascular malformation in the bowel (112603). Severe hypophosphatemia requiring intravenous phosphate in the absence of osteomalacia has also occurred following intravenous ferric carboxymaltose (112608,112610).

Oncologic ...There is a debate regarding the association between high levels of iron stores and cancer. Data are conflicting and inconclusive (1098,1099,1100,1102). Epidemiological studies suggest that increased body iron stores may increase the risk of cancer or general mortality (56703).
Occupational exposure to iron may be carcinogenic (56691). Oral exposure to iron may also be carcinogenic. Pooled analyses of population studies suggest that increasing the intake of heme iron increases the risk of colorectal cancer. For example, increasing heme iron intake by 1 mg/day is associated with an 11% increase in risk (56699,91185).

Other ...Intravenously, sodium ferric gluconate complex (SFGC) caused drug intolerance reactions in 0. 4% of hemodialysis patients including 2 patients with pruritus and one patient each with anaphylactoid reaction, hypotension, chills, back pain, dyspnea/chest pain, facial flushing, rash and cutaneous symptoms of porphyria (56527).

(Read more about IRON)

General ...Orally, pea protein seems to be well tolerated.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis in sensitive individuals.

Immunologic ...Orally, pea protein may cause allergic reactions in individuals sensitive to other foods. A case series describes 6 children who had anaphylactic reactions to pea protein present in a number of food items. Other symptoms included angioedema, urticaria, and asthma. All the children had a history of allergies to other foods including peanuts, tree nuts, chickpeas, lentils, or kidney beans (102012).

(Read more about PEA PROTEIN)

General ...Orally or intravenously, potassium is generally well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, belching, diarrhea, flatulence, nausea, and vomiting.
Serious Adverse Effects (Rare):
All ROAs: High potassium levels can cause arrhythmia, heart block, hypotension, and mental confusion.

Cardiovascular ...Orally or intravenously, high potassium levels can cause hypotension, cardiac arrhythmias, heart block, or cardiac arrest (15,16,3385,95011,95626,95630).

Gastrointestinal ...Orally or intravenously, high doses of potassium can cause, nausea, vomiting, abdominal pain, diarrhea, and flatulence (95010,95011). Bleeding duodenal ulcers have also been associated with ingestion of slow-release potassium tablets (69625,69672).

Neurologic/CNS ...Orally or intravenously, high potassium levels can cause paresthesia, generalized weakness, flaccid paralysis, listlessness, vertigo, or mental confusion (15,16,3385,95011).

(Read more about POTASSIUM)

General ...Orally, pumpkin products are generally well tolerated.
Most Common Adverse Effects:
Orally: Abdominal discomfort, diarrhea, nausea, and vomiting.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis.

Dermatologic ...There are two case reports of adult females developing substantial transient hair loss 1-3 weeks after consumption of a meal containing either bitter-tasting pumpkin or undefined squash. This adverse effect was attributed to a high concentration of cucurbitacin, which is commonly found in wild pumpkins (104535).

Gastrointestinal ...Orally, pumpkin seed oil has been reported to cause mild abdominal discomfort in clinical trials (5093,92378). There are also two case reports of adults developing severe nausea, vomiting, and diarrhea following consumption of a meal containing either bitter-tasting pumpkin or undefined squash. These adverse effects were attributed to a high concentration of cucurbitacin, which is commonly found in wild pumpkins (104535).

Immunologic ...Orally, pumpkin seed oil and pumpkin pulp have been reported to cause anaphylactic reactions in children and adults. A case review highlights 4 cases of anaphylaxis in children (3 from pumpkin pulp, 1 from pumpkin seeds), and 7 cases in adults (1 from pumpkin flesh, 6 from pumpkin seeds). Symptoms of anaphylaxis include urticaria, angioedema of the lips or face, dyspnea, dysphagia, and oropharyngeal itching and swelling. A case report describes a 2-year-old male presenting with urticaria, swollen lips, and increased dyspnea 10 minutes after ingesting pumpkin seeds. The patient was found to have elevated allergen-specific immunoglobulin E (IgE) and a positive skin-prick test for pumpkin seeds. Symptoms resolved after treatment with epinephrine, systemic glucocorticoids, salbuterol, and antihistamines (107843).
There may also be concern for allergic reaction due to inhalation or topical exposure. One case report describes an 8-year-old child developing anaphylaxis while carving a pumpkin; another highlights that inhalation of pumpkin seed flour may have potentiated anaphylaxis in 3 individuals following the ingestion of pumpkin seeds (107843). Further research is necessary to assess the relationship between anaphylaxis and route of administration.

(Read more about PUMPKIN)

General ...Orally, sodium is well tolerated when used in moderation at intakes up to the Chronic Disease Risk Reduction (CDRR) intake level. Topically, a thorough evaluation of safety outcomes has not been conducted.
Serious Adverse Effects (Rare):
Orally: Worsened cardiovascular disease, hypertension, kidney disease.

Cardiovascular ...Orally, intake of sodium above the CDRR intake level can exacerbate hypertension and hypertension-related cardiovascular disease (CVD) (26229,98176,100310,106263). A meta-analysis of observational research has found a linear association between increased sodium intake and increased hypertension risk (109398). Observational research has also found an association between increased sodium salt intake and increased risk of CVD, mortality, and cardiovascular mortality (98177,98178,98181,98183,98184,109395,109396,109399). However, the existing research is unable to confirm a causal relationship between sodium intake and increased cardiovascular morbidity and mortality; high-quality, prospective research is needed to clarify this relationship (100312). As there is no known benefit with increased salt intake that would outweigh the potential increased risk of CVD, advise patients to limit salt intake to no more than the CDRR intake level (100310).
A reduction in sodium intake can lower systolic blood pressure by a small amount in most individuals, and diastolic blood pressure in patients with hypertension (100310,100311,106261). However, post hoc analysis of a small crossover clinical study in White patients suggests that 24-hour blood pressure variability is not affected by high-salt intake compared with low-salt intake (112910). Additionally, the available research is insufficient to confirm that a further reduction in sodium intake below the CDRR intake level will lower the risk for chronic disease (100310,100311). A meta-analysis of clinical research shows that reducing sodium intake increases levels of total cholesterol and triglycerides, but not low-density lipoprotein (LDL) cholesterol, by a small amount (106261).
It is unclear whether there are safety concerns when sodium is consumed in amounts lower than the adequate intake (AI) levels. Some observational research has found that the lowest levels of sodium intake might be associated with increased risk of death and cardiovascular events (98181,98183). However, this finding has been criticized because some of the studies used inaccurate measures of sodium intake, such as the Kawasaki formula (98177,98178,101259). Some observational research has found that sodium intake based on a single 24-hour urinary measurement is inversely correlated with all-cause mortality (106260). The National Academies Consensus Study Report states that there is insufficient evidence from observational studies to conclude that there are harmful effects from low sodium intake (100310).

Endocrine ...Orally, a meta-analysis of observational research has found that higher sodium intake is associated with an average increase in body mass index (BMI) of 1. 24 kg/m2 and an approximate 5 cm increase in waist circumference (98182). It has been hypothesized that the increase in BMI is related to an increased thirst, resulting in an increased intake of sugary beverages and/or consumption of foods that are high in salt and also high in fat and energy (98182). One large observational study has found that the highest sodium intake is not associated with overweight or obesity when compared to the lowest intake in adolescents aged 12-19 years when intake of energy and sugar-sweetened beverages are considered (106265). However, in children aged 6-11 years, usual sodium intake is positively associated with increased weight and central obesity independently of the intake of energy and/or sugar-sweetened beverages (106265).

Gastrointestinal ...In one case report, severe gastritis and a deep antral ulcer occurred in a patient who consumed 16 grams of sodium chloride in one sitting (25759). Chronic use of high to moderately high amounts of sodium chloride has been associated with an increased risk of gastric cancer (29405).

Musculoskeletal ...Observational research has found that low sodium levels can increase the risk for osteoporosis. One study has found that low plasma sodium levels are associated with an increased risk for osteoporosis. Low levels, which are typically caused by certain disease states or chronic medications, are associated with a more than 2-fold increased odds for osteoporosis and bone fractures (101260).
Conversely, in healthy males on forced bed rest, a high intake of sodium chloride (7.7 mEq/kg daily) seems to exacerbate disuse-induced bone and muscle loss (25760,25761).

Oncologic ...Population research has found that high or moderately high intake of sodium chloride is associated with an increased risk of gastric cancer when compared with low sodium chloride intake (29405). Other population research in patients with gastric cancer has found that a high intake of sodium is associated with an approximate 65% increased risk of gastric cancer mortality when compared with a low intake. When zinc intake is taken into consideration, the increased risk of mortality only occurred in those with low zinc intake, but the risk was increased to approximately 2-fold in this sub-population (109400).

Pulmonary/Respiratory ...In patients with hypertension, population research has found that sodium excretion is modestly and positively associated with having moderate or severe obstructive sleep apnea. This association was not found in normotensive patients (106262).

Renal ...Increased sodium intake has been associated with impaired kidney function in healthy adults. This effect seems to be independent of blood pressure. Observational research has found that a high salt intake over approximately 5 years is associated with a 29% increased risk of developing impaired kidney function when compared with a lower salt intake. In this study, high salt intake was about 2-fold higher than low salt intake (101261).

(Read more about SODIUM)

General ...Orally, vitamin A is generally well-tolerated at doses below the tolerable upper intake level (UL).
Serious Adverse Effects (Rare):
Orally: In very high doses, vitamin A can cause pseudotumor cerebri, pain, liver toxicity, coma, and even death.

Dermatologic ...Chronic oral use of large amounts of vitamin A causes symptoms of vitamin A toxicity including dry skin and lips; cracking, scaling, and itchy skin; skin redness and rash; hyperpigmentation; shiny skin, and massive skin peeling (7135,95051). Hypervitaminosis A can cause brittle nails, cheilitis, gingivitis, and hair loss (15,95051). Adverse effects from a single ingestion of a large dose of vitamin A is more common in young children than adults (15). In children, approximately 25,000 IU/kg can cause skin redness and generalized peeling of the skin a few days later and may last for several weeks (15).

Gastrointestinal ...There is some evidence that oral vitamin A supplementation might increase the risk of diarrhea in children. Although vitamin A can prevent diarrhea and reduce mortality in malnourished children, doses as low as 10,000 IU weekly for 40 weeks have been associated with diarrhea in well-nourished children (319). Diarrhea (82326,82389), nausea (7135,100329), abdominal pain (95051), abdominal fullness (100329), and vomiting (7135,82559,95051,95055,109755) have been reported following use of large doses of oral vitamin A. Adverse effects from a single ingestion of a large dose of vitamin A is more common in young children than adults (15). In children, approximately 25,000 IU/kg can cause vomiting and diarrhea (15). Chronic use of large amounts of vitamin A causes symptoms of vitamin A toxicity including anorexia, abdominal discomfort, and nausea and vomiting (7135).

Genitourinary ...Hypervitaminosis A can cause reduced menstrual flow (15). Intravaginally, all-trans retinoic acid can cause vaginal discharge, itching, irritation, and burning (9199).

Hematologic ...Hypervitaminosis A can cause spider angiomas, anemia, leukopenia, leukocytosis, and thrombocytopenia (15,95051).

Hepatic ...Since the liver is the main storage site for vitamin A, hypervitaminosis A can cause hepatotoxicity, with elevated liver enzymes such as alanine aminotransferase (ALT, formerly SGPT) and aspartate aminotransferase (AST, formerly SGOT), as well as fibrosis, cirrhosis, hepatomegaly, portal hypertension, and death (6377,7135,95051).

Musculoskeletal ...Vitamin A can increase the risk for osteoporosis and fractures. Observational research has found that chronic, high intake of vitamin A 10,000 IU or more per day is associated with an increased risk of osteoporosis and hip fracture in postmenopausal adults, as well as overall risk of fracture in middle-aged males (7712,7713,9190). A meta-analysis of these and other large observational studies shows that high dietary intake of vitamin A or retinol is associated with a 23% to 29% greater risk of hip fracture when compared with low dietary intake (107294). High serum levels of vitamin A as retinol also increase the risk of fracture in males. Males with high serum retinol levels are seven times more likely to fracture a hip than those with lower serum retinol levels (9190). Vitamin A damage to bone can occur subclinically, without signs or symptoms of hypervitaminosis A. Some researchers are concerned that consumption of vitamin A fortified foods such as margarine and low-fat dairy products in addition to vitamin A or multivitamin supplements might cause excessive serum retinol levels. Older people have higher levels of vitamin A and might be at increased risk for vitamin A-induced osteoporosis.
Vitamin A's effects on bone resorption could lead to hypercalcemia (95051).
Hypervitaminosis can cause slow growth, premature epiphyseal closure, painful hyperostosis of the long bones, general joint pain, osteosclerosis, muscle pain, and calcium loss from the bones (15,95051). One child experienced severe bone pain after taking vitamin A 600,000 IU daily for more than 3 months (95051). Vitamin A was discontinued and symptoms lessened over a period of 2 weeks. The patient made a full recovery 2 months later.

Neurologic/CNS ...Orally, adverse effects from a single large dose of vitamin A are more common in young children than adults (15). Headache, increased cerebrospinal fluid pressure, vertigo, and blurred vision have been reported following an acute oral dose of vitamin A 500,000 IU (7135). In children, approximately 25,000 IU/kg can cause headache, irritability, drowsiness, dizziness, delirium, and coma (15). Chronic use of large amounts of vitamin A causes symptoms of vitamin A toxicity including fatigue, malaise, lethargy, and irritability (7135).
There are reports of bulging of the anterior fontanelle associated with an acute high oral dose of vitamin A in infants (7135,90784,95053,95054). In children, approximately 25,000 IU/kg can cause increased intracranial pressure with bulging fontanelles in infants (15). Also, muscular incoordination has been reported following short-term high doses of vitamin A (7135).
A case of intracranial hypertension involving diffuse headaches and brief loss of vision has been reported secondary to topical use of vitamin A. The patient was using over-the-counter vitamin A preparations twice daily including Avotin 0.05% cream, Retin-A gel 0.01%, and Isotrexin gel containing isotretinoin 0.05% and erythromycin 2%, for treatment of facial acne. Upon exam, the patient was noted to have bilateral optic disc edema. The patient discontinued use of topical vitamin A products. Two months later, the patient reported decreased headaches and an improvement in bilateral optic disc edema was seen (95056).

Ocular/Otic ...In children, oral vitamin A approximately 25,000 IU/kg can cause swelling of the optic disk, bulging eyeballs, and visual disturbances (15). Adverse effects from a single ingestion of a large dose of vitamin A are more common in young children than adults (15).

Oncologic ...There is concern that high intake of vitamin A might increase some forms of cancer. Population research suggests high vitamin A intake might increase the risk of gastric carcinoma (9194).

Psychiatric ...Chronic oral use of large amounts of vitamin A causes symptoms of vitamin A toxicity, which can include symptoms that mimic severe depression or schizophrenic disorder (7135).

Pulmonary/Respiratory ...There is some evidence that oral vitamin A supplementation might increase the risk of pneumonia and diarrhea in children. Although vitamin A can prevent diarrhea and reduce mortality in malnourished children, doses as low as 10,000 IU weekly for 40 weeks have been associated with pneumonia and diarrhea in well-nourished children (319). In preschool children, high-dose vitamin A also increases the risk of respiratory infection (82288).

Other ...Chronic use of large amounts of vitamin A (>25,000 IU daily for more than 6 years or 100,000 IU daily for more than 6 months) can cause symptoms of vitamin A toxicity including mild fever and excessive sweating (7135). High intakes of vitamin A may result in a failure to gain weight normally in children and weight loss in adults (15).

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General ...Orally, intravenously, and topically, vitamin C is well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, esophagitis, heartburn, headache, osmotic diarrhea, nausea, vomiting. Kidney stones have been reported in those prone to kidney stones. Adverse effects are more likely to occur at doses above the tolerable upper intake level of 2 grams daily.
Topically: Irritation and tingling.
Serious Adverse Effects (Rare):
Orally: There have been rare case reports of carotid inner wall thickening after large doses of vitamin C.
Intravenously: There have been case reports of hyperoxalosis and oxalate nephropathy following high-dose infusions of vitamin C.

Cardiovascular ...Evidence from population research has found that high doses of supplemental vitamin C might not be safe for some people. In postmenopausal adults with diabetes, supplemental vitamin C intake in doses greater than 300 mg per day is associated with increased risk of cardiovascular mortality. However, dietary intake of vitamin C is not associated with this risk. Also, vitamin C intake is not associated with an increased risk of cardiovascular mortality in patients without diabetes (12498).
Oral supplementation with vitamin C has also been associated with an increased rate of carotid inner wall thickening in men. There is preliminary evidence that supplemental intake of vitamin C 500 mg daily for 18 months can cause a 2.5-fold increased rate of carotid inner wall thickening in non-smoking men and a 5-fold increased rate in men who smoked. The men in this study were 40-60 years old (1355). This effect was not associated with vitamin C from dietary sources (1355).
There is also some concern that vitamin C may increase the risk of hypertension in some patients. A meta-analysis of clinical research suggests that, in pregnant patients at risk of pre-eclampsia, oral intake of vitamin C along with vitamin E increases the risk of gestational hypertension (83450). Other clinical research shows that oral intake of vitamin C along with grape seed polyphenols can increase both systolic and diastolic blood pressure in hypertensive patients (13162).

Dental ...Orally, vitamin C, particularly chewable tablets, has been associated with dental erosion (83484).

Dermatologic ...Topically, vitamin C might cause tingling or irritation at the site of application (6166). A liquid containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) has been reported to cause mild tingling and skin tightness (102355). It is unclear if these effects are due to vitamin C, the other ingredients, or the combination.

Gastrointestinal ...Orally, the adverse effects of vitamin C are dose-related and include nausea, vomiting, esophagitis, heartburn, abdominal cramps, gastrointestinal obstruction, and diarrhea. Doses greater than the tolerable upper intake level (UL) of 2000 mg per day can increase the risk of adverse effects such as osmotic diarrhea and severe gastrointestinal upset (3042,4844,96707,104450). Mineral forms of vitamin C, such as calcium ascorbate (Ester-C), seem to cause fewer gastrointestinal adverse effects than regular vitamin C (83358). In a case report, high dose intravenous vitamin C was associated with increased thirst (96709).

Genitourinary ...Orally, vitamin C may cause precipitation of urate, oxalate, or cysteine stones or drugs in the urinary tract (10356). Hyperoxaluria, hyperuricosuria, hematuria, and crystalluria have occurred in people taking 1 gram or more per day (3042,90943). Supplemental vitamin C over 250 mg daily has been associated with higher risk for kidney stones in males. There was no clear association found in females, but the analysis might not have been adequately powered to evaluate this outcome (104029). In people with a history of oxalate kidney stones, supplemental vitamin C 1 gram per day appears to increase kidney stone risk by 40% (12653). A case of hematuria, high urine oxalate excretion, and the presence of a ureteral stone has been reported for a 9-year-old male who had taken about 3 grams of vitamin C daily since 3 years of age. The condition resolved with cessation of vitamin C intake (90936).

Hematologic ...Prolonged use of large amounts of vitamin C can result in increased metabolism of vitamin C; subsequent reduction in vitamin C intake may precipitate the development of scurvy (15). In one case, a patient with septic shock and a large intraperitoneal hematoma developed moderate hemolysis and increased methemoglobin 12 hours after a high-dose vitamin C infusion. The patient received a blood transfusion and the hemolysis resolved spontaneously over 48 hours (112479).

Neurologic/CNS ...Orally, the adverse effects of vitamin C are dose-related and include fatigue, headache, insomnia, and sleepiness (3042,4844,83475,83476).

Renal ...Hyperoxalosis and oxalate nephropathy have been reported following high-dose infusions of vitamin C. Hyperoxalosis and acute kidney failure contributed to the death of a 76-year-old patient with metastatic adenocarcinoma of the lung who received 10 courses of intravenous infusions containing vitamins, including vitamin C and other supplements over a period of 1 month. Dosages of vitamin C were not specified but were presumed to be high-dose (106618). In another case, a 34-year-old patient with a history of kidney transplant and cerebral palsy was found unresponsive during outpatient treatment for a respiratory tract infection. The patient was intubated for acute hypoxemic respiratory failure, initiated on vasopressors, hydrocortisone, and antibacterial therapy, and received 16 doses of vitamin C 1.5 grams. Serum creatinine level peaked at greater than 3 times baseline and the patient required hemodialysis for oliguria and uncontrolled acidosis. Kidney biopsy revealed oxalate nephropathy with concomitant drug-induced interstitial nephritis (106625). In another case, a 41-year-old patient with a history of kidney transplant presented with fever, nausea, and decreased urine output 4 days after receiving intravenous vitamin C 7 grams for urothelial carcinoma. Serum creatinine levels increased from 1.7 mg/dL to 7.3 mg/dL over those 4 days, and hemodialysis was initiated 3 days after admission due to anuria. Renal biopsy confirmed the diagnosis of acute oxalate nephropathy (109962).

Other ...Intravenously, hypernatremia and falsely elevated ketone levels is reported in a patient with septic shock and chronic kidney disease after a high-dose vitamin C infusion. The hypernatremia resolved over 24 hours after cessation of the infusion (112479).

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General ...Orally, xanthan gum can cause flatulence and abdominal distention (4916,4918). Topically, it has been reported to cause allergic reactions (100914).

Immunologic ...An itchy, burning dermatitis was reported in a 9-year old girl after application of a sunscreen product containing xanthan gum. Patch testing with the separate ingredients of the sunscreen identified xanthan gum as the reacting agent, and demonstrated a dose-dependent effect with 1% and 10% solutions (100914).

Pulmonary/Respiratory ...Occupational exposure in workers handling xanthan gum powder can cause flu-like symptoms and nose and throat irritation without acute or chronic loss of pulmonary function (4913).

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