Caribbean Tanning Secret [Discontinued] by Futurebiotics

POSSIBLY EFFECTIVE

• Acne. Topical aloe gel may reduce acne lesions when used with topical tretinoin in children and adults with acne. Details: One clinical trial in children and adults with acne shows that topical application of a gel containing aloe 50% in the morning and evening, in addition to topical application of tretinoin 0.025% cream and twice daily cleansing with a medical soap, improves acne lesions by approximately 35% more than using the same treatments without aloe (90124).
• Burns. Topical aloe gel or cream may reduce healing time in patients with superficial or partial thickness burns. Details: A meta-analysis of four small clinical trials in patients with second-degree burns shows that use of topical aloe vera reduces time to healing by about 4.4 days when compared to control groups treated with silvadene, silver sulfadiazine, or gauze containing 0.5% chlorhexidine acetate (110209). Most clinical research shows that applying aloe gel or cream topically up to twice daily reduces healing time when compared with silver sulfadiazine (19771,110210,110212), framycetin (19775), vaseline gauze (19773), or placebo (101,97320) in patients with superficial or partial thickness burns. Topical application of aloe cream up to twice daily might also decrease wound size when compared with silver sulfadiazine and framycetin (19771,19775). In addition, some clinical research in patients with burns caused by sulfur mustard shows that applying cream containing aloe and olive oil twice daily for 6 weeks improves pruritus similarly to betamethasone 0.1% cream and may lead to further reductions in excoriation and fissure (19768). However, some preliminary clinical research shows that applying fresh aloe mucilage or aloe extract daily is no more effective than silver sulfadiazine for reducing wound healing time in patients with superficial or partial thickness burns (19774,19776).
• Constipation. Oral aloe latex may improve symptoms in patients with constipation; however, the U.S. Food and Drug Administration (FDA) has banned the use of aloe latex as a laxative due to safety concerns. Details: Taking aloe latex 100-200 mg daily or aloe extract 50 mg as a stimulant laxative seems to relieve constipation due to the cathartic effects of the anthraquinones in the aloe (4,5,8). Taking 1-3 capsules of a formulation containing aloe 150 mg, celandine 300 mg, and psyllium 50 mg also seems to improve stool consistency and the mean number of stools in patients with chronic constipation when compared with placebo (19747). However, in 2002, the U.S. FDA banned the use of aloe latex for constipation due to safety concerns (8229,8443).
• Diabetes. Oral aloe may reduce blood glucose and glycated hemoglobin (HbA1c) in patients with diabetes. It may be most effective in patients with fasting blood glucose levels of 200 mg/dL or greater. Details: Most clinical research in adults with prediabetes and diabetes shows that taking aloe vera orally can reduce fasting blood glucose by 30-47 mg/dL and HbA1c by 0.41% to 1% (12164,17488,17489,19756,95943,95945,95946). One meta-analysis of 92 patients shows that aloe vera is associated with a larger overall reduction of fasting blood glucose in those with a baseline fasting blood glucose level greater than or equal to 200 mg/dL (95945). Another meta-analysis of 206 patients shows that aloe vera increases high-density lipoprotein (HDL) levels and reduces triglyceride, total cholesterol, and low-density lipoprotein (LDL) levels when compared with placebo in adults with prediabetes and untreated diabetes (95943). These analyses include studies that used multiple forms of aloe vera, including gel powder, extract, raw crushed leaves, and fresh extracted juice, as well as multiple doses ranging from 100-1000 mg of powder and 15-150 mL of juice taken for durations ranging from 4-14 weeks. Significant heterogeneity between studies, small sample sizes, and wide variability in the form and dose of aloe used limit the validity of these findings and the ability to identify an effective dose (95943,95945,95946). Additionally, some research has shown no benefit. This may be due to the different forms and doses of aloe used. One clinical study shows that taking aloe gel as 15 mL twice daily or taking aloe juice 15 mL twice daily does not decrease glucose levels in patients with type 2 diabetes (17420). Other clinical research shows that taking a specific aloe gel complex (Aloe QDM complex, Univera Inc.) containing processed aloe gel 147 mg twice daily for 8 weeks does not affect glycemic indices when compared with placebo in patients with diabetes or prediabetes (90121).
• Genital herpes. Topical aloe extract cream may improve healing of genital herpes lesions. Details: Clinical research in males with genital herpes shows that applying a cream containing aloe extract 0.5% three times daily, 5 days weekly, for up to 2 weeks increases healing rates when compared with aloe gel or placebo. The mean time to healing after application of the aloe extract was 5 days, compared with 12 days with placebo (12164,19745,19746).
• Lichen planus. Rinsing the mouth with aloe-containing mouthwash or applying aloe gel to the mouth or vulva may reduce pain and improve lesion healing in patients with lichen planus. Details: Clinical research in patients with oral lichen planus shows that using 0.4 mL of mouthwash containing aloe gel 70% three times daily for 12 weeks or applying a gel containing aloe mucilage 70% twice daily for 8 weeks is up to 6 times more likely to reduce pain when compared with placebo (19762,19763,19764). However, these findings are questionable due to poor study design. Other clinical research in patients with oral lichen planus shows that using 2 tablespoons of aloe-containing mouthwash four times daily for a month, or applying aloe gel three times daily for 8 weeks, reduces pain and improves lesion healing at least as much as triamcinolone acetonide paste (0.1% in one study) (19765,90130). However, aloe gel may not be as beneficial as laser therapy. A clinical study in patients with lichen planus show that applying a gel containing aloe powder 500 mg to the affected site three times daily for 2 months is less effective for improving pain and lesion healing than receiving low-level laser therapy twice weekly for 2 months. However, no between-group differences were maintained at 7 months after treatment completion (108722). A network meta-analysis of 2 small clinical trials shows that applying aloe trails only purslane of the herbal agents studied with regard to clinical improvement as measured by the Thongprasom scale. However, aloe does not seem to improve complete clinical resolution, clinical scores, or pain (111640). In patients with vulval lichen planus, clinical research shows that topical application with aloe gel twice daily for 8 weeks increases the number of patients who experience clinical improvement of at least 50% when compared with placebo (19766).
• Obesity. Oral aloe gel may modestly reduce body weight and fat mass in adults who are overweight or obese. Details: One clinical trial in overweight and obese adults with diabetes or prediabetes shows that taking a specific aloe gel complex (Aloe QDM complex, Univera Inc.) containing processed aloe gel 147 mg twice daily for 8 weeks reduces body weight by 0.6 kg and fat mass by 1 kg when compared with placebo (90121).
• Oral submucous fibrosis. Topical aloe may reduce burning sensations in patients with oral submucous fibrosis, but it may not improve mouth opening, tongue protrusion, or cheek flexibility in these patients. Details: A meta-analysis of five small clinical studies in patients with oral submucous fibrosis shows that topical application of aloe gel for 3 months reduces burning sensation, possibly for up to two months after treatment, when compared with placebo or active control. A network meta-analysis also found that aloe is most effective in reducing burning sensation, ranked only after treatment with corticosteroids, hyaluronidase, and antioxidants (113514). However, aloe does not seem to improve mouth opening, tongue protrusion, or cheek flexibility (100256). One of the studies included in the analysis used a specific aloe gel (Sheetal lab Surat) 5 mg applied topically on each side of the buccal mucosa three times daily for 3 months (90131). All of the studies included in the analysis were conducted in India, so it is unclear if the results are generalizable to other geographic locations. Limited research has also evaluated the use of topical and oral aloe vera in combination. A small clinical study shows that consuming pure aloe vera juice (Hamant Sai, Sun Vision Company) 30 mL twice daily and applying pure aloe vera gel (Hamant Sai, Sun Vision Company) three times daily for 3 months improves cheek flexibility and tongue protrusion when compared with a treatment regimen consisting of intralesional injections of hydrocortisone acetate 25 mg and hyaluronidase 1500 IU weekly for 6 weeks and supplementation with Cap SM Fibro (Indoco Remedies) twice daily for 3 months. Both treatment regimens show an improvement in mouth opening and burning sensation when compared to baseline, with the aloe vera treatment producing a more rapid improvement in burning sensation (95944). It is not clear how this combination of oral and topical aloe vera compares with topical aloe vera alone.
• Psoriasis. Topical aloe extract cream may reduce erythema and scaling and improve the resolution of psoriatic plaques in patients with psoriasis. Limited research suggests that topical aloe gel does not have the same effects. Details: Applying aloe extract 0.5% cream topically three times daily for 4 weeks significantly improves and increases the resolution of psoriatic plaques when compared with placebo (101,12096,12164). Aloe extract cream also seems to reduce desquamation, erythema, and infiltration (12096). Other preliminary clinical research shows that applying cream containing aloe mucilage 70% twice daily for 8 weeks improves psoriasis severity more effectively than triamcinolone 0.1% cream, although both treatments had similar effects on dermatology-specific quality of life (19741). Treatment with aloe gel does not seem to improve erythema, infiltration, and desquamation associated with psoriasis when compared with placebo (19748).
• Traumatic oral ulcers. Topical aloe gel may prevent oral ulcers after application of orthodontic appliances in adolescents and adults. Details: Clinical research in patients aged 12 years and older shows that applying a gel containing aloe 80% to the gums twice daily for one month after the cementation of orthodontic appliances prevents the development of mouth ulcers when compared with a chlorhexidine gel. Ulcers occurred in about 6% of patients using the aloe gel compared with 81% of those using the chlorhexidine gel. Bleeding and inflammation were also reduced (103305).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alveolar osteitis. It is unclear if topical aloe or the aloe constituent acemannan is beneficial in patients with alveolar osteitis. Details: One small clinical trial in patients with alveolar osteitis shows that applying a patch containing the aloe constituent acemannan (SaliCept patch) to the tooth socket, once after curettage and irrigation and again 3 days later, reduces pain intensity and improves clinical symptoms when compared with curettage and irrigation alone (19754).
• Amenorrhea. Although there has been interest in using oral aloe for amenorrhea, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Anal fissures. It is unclear if topical aloe is beneficial in patients with anal fissures. Details: One small clinical study in patients with chronic anal fissures shows that applying an aloe cream containing 0.5% powdered spray-dried inner aloe leaf juice (Zarban Phyto-Pharmaceutical Co) three times daily for at least 3 weeks, as an adjuvant to sitz baths three times daily, using a laxative, and eating a full fiber diet, improves pain, wound healing, and bleeding severity when compared with placebo (90129).
• Asthma. Although there has been interest in using oral aloe for asthma, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Atopic dermatitis (eczema). Topical aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical trial in patients with atopic dermatitis shows that application of a specific combination cream (Olivederma, Kimi Daru Pharmaceutical Co.) containing aloe gel and virgin olive oil twice daily for 6 weeks improves disease severity and quality of life when compared with betamethasone cream (105020). It is unclear if this effect is due to aloe, olive oil, or the combination.
• Breast engorgement. It is unclear if topical aloe improves lactation-associated breast pain. Details: Meta-analyses of 4-5 clinical trials in lactating patients show that use of topical aloe modestly reduces nipple/breast pain and irritation when compared with no treatment, routine care with topical breast milk or breast massage, or treatment with lanolin (110213). However, studies included in this analysis were not specific to breast engorgement.
• Burning mouth syndrome. It is unclear if topical aloe is beneficial in patients with burning mouth syndrome. Details: One small clinical trial in patients with chronic burning mouth syndrome shows that applying 0.5 mL of aloe 70% gel to sore areas on the tongue three times daily prior to wearing a tongue protector for 12 weeks does not improve pain or symptoms when compared with placebo gel or using the tongue protector alone in patients with chronic burning mouth syndrome (90127). However, differences in baseline pain ratings between study groups limit the validity of these findings.
• Cancer. Oral aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with lung cancer shows that, when administered with standard chemotherapy, three daily doses of 10 mL of a mixture consisting of fresh aloe leaves 300 grams plus honey 500 grams dissolved in 40 mL of alcohol 40% increases the rate of complete response, partial response, or disease control when compared with chemotherapy alone (19752).
• Canker sores. Small clinical studies suggest that applying the aloe constituent acemannan to cancer sores may reduce ulcer size, but not pain. However, the effect of aloe is unclear. Details: Meta-analyses of clinical research show that topical aloe is no more effective than control interventions for reducing the size and pain of oral ulcers (110216). Control interventions have included carrier gel or triamcinolone acetonide 0.1% (19751,110216). However, a recent clinical trial shows that topical aloe gel (G.U.M Canker-X, Sunstar Americas, Schaumburg, USA) after meals and before bedtime for 5 days is more effective than amlexanox 5% paste and placebo for reducing pain and the size of canker sores in patients with recurrent symptoms (110215). Other small clinical trials have investigated the effects of fermented aloe or the aloe constituent acemannan. One small clinical trial in adults with recurrent canker sores shows that applying a fermented aloe gel to oral ulcers three times daily seems to accelerate healing time when compared with chitosan gel (104173). Another small clinical trial in patients with canker sores shows that using a wound dressing containing the aloe constituent acemannan (Carrisyn Gel Wound Dressing) shortens the average healing time of canker sores when compared with an oral analgesic (Orabase-Plain) (19750). Other clinical research shows that applying acemannan 0.5% in Carbopol 934P NF three times daily for 7 days reduces ulcer size, but not pain, when compared with Carbopol 934P NF alone in patients with canker sores (90123). However, applying triamcinolone acetonide 0.1% appears to be more effective in reducing pain and similarly effective in reducing ulcer size when compared with acemannan 0.5% (90123).
• Common cold. Although there has been interest in using oral aloe for the common cold, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Dental plaque. Using aloe-containing toothpaste may reduce dental plaque in adults; however, it is unclear if this is more effective than fluoride-containing toothpaste. Rinsing with an aloe-containing mouthwash may reduce dental plaque in children. Details: One small clinical trial in adults shows that brushing teeth with a dentifrice containing aloe gel (Forever Bright, Forever Living Products) three times daily for 30 days does not reduce the occurrence of plaque better than a fluoridated dentifrice (Sorriso Dentes Brancos, Kolynos do Brasil), although both treatments seem to show improvement when compared to baseline (19755). Another small clinical study in adults with gingivitis shows that using toothpaste containing aloe daily for 24 weeks reduces plaque more effectively than placebo or triclosan-containing toothpaste (19760). In children aged 8-14 years with mild plaque, using a mouth wash containing aloe vera 7% twice daily for 4 weeks reduced plaque by a large amount when compared with placebo. In addition, it was as effective as chlorhexidine 0.2% (103306).
• Depression. Although there has been interest in using oral aloe for depression, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Diabetic foot ulcers. It is unclear whether topical aloe is beneficial for patients with diabetic foot ulcers. Details: One small clinical trial in patients with a stage 1 or 2 diabetic foot ulcer who are receiving oral antibiotics shows that applying a topical product containing aloe and great plantain twice daily for 4 weeks reduces ulcer surface area and time to healing, but not ulcer depth, when compared with antibiotics alone (97323). The effect of applying aloe gel alone without concomitant oral antibiotic therapy is unknown.
• Diaper rash. Topical aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical trial shows that applying a cream containing aloe gel and olive oil three times daily for 5-10 days reduces diaper rash severity in children less than 3 years of age when compared to baseline; however, it does not seem to be as effective as calendula ointment (19779). The validity of this finding is limited by the lack of a placebo group.
• Dry mouth. It is unclear if rinsing with an aloe-containing mouthwash is beneficial for dry mouth. Details: In patients with dry mouth related to type 2 diabetes, clinical research shows that an aloe vera 50% mouthwash, as 20 mL swished and spit three times daily for 14 days, modestly reduces symptoms of dry mouth when compared with rinsing with a saline control mouthwash (106068). The validity of this study is limited due to unclear reporting.
• Dry skin. Topical aloe or oral aloe sterols may improve some measures of dry skin. However, findings are mixed due to the use of varied formulations and doses. Details: One small clinical trial shows that applying a cream containing freeze-dried aloe extract 0.1% to 0.5% to the skin for 2 weeks increases the amount of water in the stratum corneum, but does not reduce transepidermal water loss, when compared with placebo (19758). Another small clinical study in females with occupational dry skin shows that wearing gloves coated in aloe 8 hours daily for 30 days improves symptoms of dry skin when compared with no treatment (19759). However, it is not clear if the benefits resulted from applying aloe or wearing gloves. One small clinical trial in healthy females shows that consumption of a yogurt containing 500 mg of aloe vera gel powder (0.4 mg of aloe sterol) daily for 12 weeks increases skin hydration, skin elasticity, and collagen content of the dermis while reducing markers of skin fatigue and transepidermal water loss when compared with placebo (95942). However, another study in healthy females shows that taking aloe sterol-enriched aloe extract 0.5 grams daily for 12 weeks does not improve skin hydration when compared with placebo, although redness, itching, collagen content, and transepidermal water loss were improved (101577).
• Epilepsy. Although there has been interest in using oral aloe for epilepsy, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Frostbite. Although there has been interest in using topical aloe for frostbite, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Gingivitis. Using aloe-containing toothpaste may reduce gingivitis in adults, but it does not seem to be more effective than fluoride-containing toothpaste. Rinsing with an aloe-containing mouthwash may reduce gingivitis in children. Details: One small clinical trial in adults shows that brushing teeth with a dentifrice containing aloe gel (Forever Bright, Forever Living Products) three times daily for 30 days does not reduce the occurrence of gingivitis more effectively than a fluoridated dentifrice (Sorriso Dentes Brancos, Kolynos do Brasil), although both treatments seem to show improvement when compared to baseline (19755). Another small clinical study in adults with gingivitis shows that using aloe-containing toothpaste daily for 24 weeks reduces gingivitis more effectively than placebo, but not more than triclosan-containing toothpaste (19760). In children aged 8-14 years with mild gingivitis, using a mouthwash containing aloe vera 7% twice daily for 4 weeks reduced gingivitis by a large amount when compared with placebo. In addition, it was as effective as chlorhexidine 0.2% (103306).
• Heart failure. It is unclear if oral aloe is beneficial in patients with systolic heart failure. Details: A very small clinical study in adults with moderate to moderately severe chronic systolic heart failure shows that taking aloe vera gel capsules 150 mg twice daily for 8 weeks in addition to standard treatment decreases New York Heart Association (NYHA) functional class, improves Minnesota Living with Heart Failure Questionnaire (MLHFQ) total, physical, emotional, and social scores, and enhances sleep quality but does not reduce the severity of obstructive sleep apnea scores or improve six-minute walk test distance when compared with placebo (111663). The study may have been inadequately powered to detect a difference between groups. Additionally, the validity of these effects may be limited by the small sample size.
• Hematopoietic stem cell transplant (HSCT). Oral and topical aloe have only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients undergoing hematopoietic stem cell transplantation shows that treatment with colostrum and aloe orally (Remargin Colostrum Gastro-Gel, Solimè srl, Cavriago, Reggio Emilia, Italy) and as a mouthwash (Remargin Colostrum OS, Solimè srl, Cavriago, Reggio Emilia, Italy) modestly reduces the risk and duration of severe oral mucositis and febrile neutropenia when compared with historical values. There was no effect on the duration of neutropenia, the length of hospital stay, pain, or duration of medications. All patients were also given standard care. The mouthwash was used after each oral hygiene, and the oral treatment was 3 to 5 times daily depending on symptoms (110211).
• Hepatitis. It is unclear if oral aloe is beneficial in patients with hepatitis. Details: One small clinical trial in patients with liver fibrosis primarily caused by hepatitis B or hepatitis C shows that taking a high molecular weight fraction of aloe 0.05 grams three times daily for 12 weeks reduces fibrosis, attenuates liver enzyme activity, and decreases hepatic glutathione content when compared with placebo (19780).
• HIV/AIDS. Small clinical studies suggest that oral aloe or the aloe constituent acemannan may not improve CD4 counts or viral load in patients with HIV. Details: One small clinical trial in patients with HIV shows that taking the aloe constituent, acemannan, 400 mg four times daily does not significantly improve CD4 counts, ratio of CD4 to CD8, or viral load when compared with placebo (19851). Another small clinical study in patients with HIV shows that taking aloe gruel 30-40 mL daily does not improve CD4 counts when compared with those treated with antiretroviral therapy, although both groups show similar increases in weight compared to baseline (19852).
• Hyperlipidemia. Although there has been interest in using oral aloe for hyperlipidemia, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Hypertrophic scars. Topical aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical trial in patients undergoing median sternotomy shows that applying a silicone gel containing aloe extract and other herbal extracts (Bangkok Botanica) to postoperative hypertrophic scars for 6 months reduces the height of the scar and improves pliability by a moderate amount when compared with a silicone placebo gel. There was no effect on pigmentation or vascularity (102793). It is unknown whether any benefit is related to aloe, other ingredients, or their combination.
• Influenza. Oral aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy adults shows that taking a combination supplement containing aloe vera gel, rosemary, and poria mushrooms twice daily 28 days before administering the influenza vaccine and 28 days after vaccination does not improve immunologic markers or reduce symptom severity, symptom duration, frequency of upper respiratory tract infection symptoms, or the use of cold and flu medications when compared with placebo (111921).
• Irritable bowel syndrome (IBS). Small clinical studies suggest that oral aloe extract or juice may not improve symptoms in patients with IBS. Details: Most research suggests that aloe is not effective for improving symptoms of IBS; however, the available evidence is of low-quality, with some studies having high dropout rates or inadequate power to detect significant differences. Two clinical trials show that taking a specific aloe extract (AVH200, Calmino Group AB) 250-500 mg twice daily for 4 weeks does not improve IBS-related symptoms or response rates when compared with placebo (101579,104169), although one of these studies did find a trend toward a higher response rate, defined as a 50% or greater improvement in symptom scores, with aloe over placebo (104169). Also, a pooled analysis of these two studies shows that taking this specific product improves IBS-related pain severity and frequency in patients with diarrhea-prominent IBS (IBS-D) when compared with placebo, but does not seem to improve stool consistency or frequency (108718). Clinical trials evaluating aloe juice 50 mL four times daily for 1 month or 60 mL twice daily for 5 months show no significant improvement in quality of life scores or IBS symptoms when compared with placebo (104170,104171), although one study did find a trend toward improved response in patients with IBS-D (104171). Despite a lack of significant findings in the individual studies, a pooled analysis of the two smallest studies above (104169,104171) shows that aloe extract or juice, taken for 4 weeks, may increase the rate of symptom response by almost 70% when compared with placebo (103307).
• Nipple Fissures. It is unclear if application of an aloe poultice improves nipple-related complications of breastfeeding, such as nipple fissures. Details: A clinical study in females who have just given birth and are breastfeeding for the first time shows that applying a poultice containing aloe gel to the nipples after breastfeeding six times daily for 5 days improves nipple eschar when compared with no treatment. Although there were modest improvements in other outcomes, such as redness, fissures, and epidermolysis, these differences were not significant (108721). Participants were instructed to clean with purified water before the next breastfeeding session.
• Multiple sclerosis (MS). Although there has been interest in using oral aloe for MS, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Oral mucositis. Small clinical studies suggest that oral aloe juice or application of aloe solution inside the mouth may prevent oral mucositis in patients receiving chemotherapy or radiation. Details: Some clinical research shows that drinking 15 mL of juice containing aloe 80% three times daily during radiation therapy decreases the risk of developing moderate or severe mucositis by approximately 39% when compared with placebo (19767,19964). In addition, in children aged 3-6 years undergoing chemotherapy for leukemia, application of a solution containing aloe 70% twice daily inside the mouth, starting three days before chemotherapy, reduces the severity of oral mucositis and delays its onset by 2 weeks when compared with sodium bicarbonate 5% (103304). Other clinical research in adults with head and neck cancer shows that rinsing and then swallowing 20 mL of a solution containing aloe juice 94.5% four times daily throughout the course of radiation therapy does not prevent mucositis when compared with placebo (19963). However, this study was not adequately powered to detect significant differences between study groups. Aloe has also been evaluated in combination with other ingredients for the treatment of oral mucositis. Preliminary clinical research in patients undergoing hematopoietic stem cell transplantation shows that treatment with colostrum and aloe orally (Remargin Colostrum Gastro-Gel, Solimè srl, Cavriago, Reggio Emilia, Italy) and as a mouthwash (Remargin Colostrum OS, Solimè srl, Cavriago, Reggio Emilia, Italy) modestly reduces the risk and duration of severe oral mucositis when compared with historical values. There was no effect on overall risk or time of onset of mucositis. All patients were also given standard care. The mouthwash was used after each oral hygiene, and the oral treatment was 3 to 5 times daily depending on symptoms (110211). Another small clinical study in adults with head and neck cancer receiving radiotherapy shows that rinsing with 5 mL of a mouthwash containing aloe, German chamomile, peppermint oil, and honey 3 times daily for 60 seconds for 6 weeks starting on the first day of radiotherapy reduces oral mucositis incidence, severity, and pain when compared with chlorhexidine and placebo (111291). It is unclear if these findings are due to aloe, other ingredients, or the combination.
• Osteoarthritis. Although there has been interest in using oral and topical aloe for osteoarthritis, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Peptic ulcers. Although there has been interest in using oral aloe for peptic ulcers, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Periodontitis. It is unclear if application of aloe inside the mouth is beneficial for chronic periodontitis. Details: A meta-analysis of small clinical studies in patients with chronic periodontitis shows that using various aloe-containing gels, mouthwashes, and toothpastes improves plaque index when compared with placebo or other treatments (i.e., chlorhexidine rinse, metformin, and tea tree oil). The effect of these aloe products on gingival index could not be determined (108719). The validity of this finding is limited by the variety of aloe formulations and comparators used in the included studies.
• Pressure ulcers. It is unclear if topical aloe is beneficial for the prevention or treatment of pressure ulcers. Details: One small clinical study shows that applying a gel containing the aloe constituent acemannan to pressure ulcers daily for 10 weeks does not reduce the time to healing when compared with management with moist saline gauze (12160,19853). Another small clinical study conducted in Iran in patients with category II pressure ulcers shows that applying topical aloe vera gel after cleaning with normal saline and prior to dressing daily for 15 days reduces pain during dressing changes when compared with normal saline dressing (113672). Other clinical research shows that cleansing wounds with a saline spray containing aloe, silver chloride, and decyl glucoside for 2 weeks improves pressure ulcer healing when compared with isotonic saline spray (19854). It is unclear if this improvement is due to aloe, other ingredients, or the combination in the spray. Aloe has also been evaluated for the prevention of pressure ulcers. A small clinical study in hospitalized patients in an orthopedic ward shows that applying aloe vera gel to the hips, sacrum, and heels twice daily for 10 days reduces pressure ulcer occurrence to 3 of 39 patients, compared to 12 of 38 patients of those receiving placebo (98816). However, methodological limitations with this study, including differences in how the gels were applied, limit the reliability of these results. A clinical study in hospitalized patients receiving intensive care has evaluated either aloe gel 94%, olive oil 100%, or a compounded product containing aloe vera and olive oil in a 3:2 ratio, applied to pressure areas as 10-15 mL every 8 hours. At the end of 30 days, pressure ulcers occurred in 17% of patients receiving the combination product, 20% receiving olive oil, 33% receiving aloe gel, and 37% receiving standard care, suggesting that any benefit may be due to olive oil (108723).
• Radiation dermatitis. There is conflicting evidence about the effectiveness of topical aloe gel for preventing or delaying dermatitis in patients undergoing radiation therapy. These conflicting findings may be due to differences in study designs, products used, and application practices. Details: Two meta-analyses of clinical trials, some of which overlap, in patients with various types of cancer shows that topical aloe does not reduce the incidence or severity of radiation dermatitis (110325,113674) and does not reduce the incidence of erythema, pruritis, moist desquamation, or dry desquamation when compared with control (110325). However, the included studies are limited by a lack of blinding, questionable methodological quality, and a high risk of bias. In contrast, another meta-analysis of generally poor quality randomized controlled trials shows that topical pre-treatment application with aloe as gel, cream, lotion, or fresh plant reduces the risk of radiation dermatitis by 23%, especially mild to moderate radiation dermatitis, when compared with a control group not treated with aloe (110214). One U.S. study included in the analysis shows that applying aloe 98% gel twice daily starting within three days of radiation initiation does not reduce radiation dermatitis when compared with a placebo gel or no treatment (12163). Other research has focused on specific side effects. One clinical trial shows that applying aloe 98% gel three times daily throughout radiation treatment and after treatment does not seem to reduce symptoms of radiation dermatitis in patients being treated for breast cancer (12098). Some research shows that applying aloe 100% gel 6-8 times daily might prolong the time before radiation-related side effects occur, but only when the cumulative dose of radiation is high (>2,700 cGy) (12159). In addition, applying aloe-based gel once daily after radiation treatment is less effective than applying anionic phospholipid-based cream for reducing dryness, erythema, and peeling in children being treated for Hodgkin disease (19855). Aloe has also been evaluated in combination with other ingredients. A small cohort study in patients with head and neck cancer receiving radiation therapy shows that applying aloe 2% and radish 4% gel twice daily until ten days after the last radiotherapy session prevents radiation dermatitis as shown by fewer cases of radiation dermatitis in the 10th, 30th, and 35th radiation sessions when compared with placebo. Furthermore, after the 35th session, the subjects prophylactically treated with the aloe and radish gel had milder grades of radiation dermatitis when compared with control (111662). A preliminary clinical study shows that applying a specific cream product (Radioskin 2, Herbalab di Perazza Massimiliano Company), which contains aloe, ginkgo extract, and metal esculetina, along with another specific cream product (Radioskin 1, Herbalab di Perazza Massimiliano Company), which contains alga atlantica and ethylbisiminomethylguaicolo manganese cloruro, may improve skin hydration and reduce skin toxicity associated with radiation therapy in patients with breast cancer (89727). These creams were applied topically 2-3 times daily at least 3 hours before and after radiation treatment, from 15 days prior to radiation until one month after completion.
• Radiation proctopathy. It is unclear if topical aloe is beneficial for the prevention or treatment of radiation proctopathy. Details: One very small clinical study in females with radiation proctopathy shows that applying 1 gram of an ointment containing aloe vera 3% rectally twice daily in conjunction with taking sulfasalazine 500 mg four times daily for 4 weeks modestly reduces diarrhea, fecal urgency, radiation toxicity, and clinical symptoms when compared with sulfasalazine alone (95941). This same product, applied twice daily for 6 weeks starting on the first day of radiotherapy, has also been evaluated for the prevention of radiation proctopathy. One small clinical study in patients with pelvic cancer shows that applying this ointment prevents proctopathy-related diarrhea, rectal bleeding, and fecal urgency when compared with placebo. Proctopathy-related symptoms occurred in 5% of patients using aloe, compared with 65% of those using placebo. However, there was no difference in rectal pain, constipation, or symptoms of cystitis between groups (101578). A very small clinical study in patients with colorectal cancer shows that applying this ointment prevents proctopathy-related diarrhea and reduces proctopathy severity, but does not improve rectal bleeding, rectal pain, fecal urgency, or symptoms of cystitis, when compared with placebo (108717). Reasons for discrepancies are unclear but might relate to differences in cancer diagnosis and radiation regimens.
• Scabies. It is unclear if topical aloe is beneficial in patients with scabies. Details: One small open-label clinical study in children and adults with scabies shows that application of crude aloe gel for 3 consecutive days, repeated again after one week, may reduce itching and lesions similar to benzyl benzoate lotion in patients with scabies when compared to baseline (19769). The validity of this finding is limited by the lack of a placebo group.
• Seborrheic dermatitis. It is unclear if topical aloe is beneficial in patients with seborrheic dermatitis. Details: One small clinical study in adults with seborrheic dermatitis shows that applying aloe 30% emulsion twice daily for 4-6 weeks reduces scaling, itching, and the number of sites involved, but not erythema, when compared with placebo (19749).
• Stretch marks (striae gravidarum). It is unclear if topical aloe is effective for the prevention or treatment of stretch marks. Details: One small clinical trial in nulliparous patients shows that topical application of a cream containing aloe twice daily, starting at gestational week 16-18, reduces erythema and itching related to abdominal stretch marks, but does not seem to decrease the number of stretch marks, when compared with a base cream (97322). Aloe gel has also been evaluated in combination with fractional carbon dioxide (CO2) laser treatments. A small clinical trial shows that applying a gel containing aloe 87.4% twice daily for up to one month after each of three CO2 laser treatments improves the texture of the skin for up to 6 months after the last laser treatment when compared to baseline. This was as effective as topical recombinant human epidermal growth factor (rhEGF) and CO2 laser treatments. However, when specific sites were examined, only the texture of stretch marks on the buttocks were improved, and these improvements were less than those seen with rhEGF (101580). The effect of aloe for the prevention of stretch marks is unknown.
• Sunburn. Although there has been interest in using topical aloe for sunburn, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Tungiasis. Topical aloe has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One clinical study shows that applying a product containing coconut oil, jojoba oil, and aloe leaf extract (Zanzarin, Engelhard Arzneimittel GmbH & Co. KG) to the feet twice daily for one-week intervals seems to reduce the number of embedded sandfleas in individuals with tungiasis when compared with a control group (19778). It is not clear if this effect is due to aloe, the other ingredients, or the combination.
• Ulcerative colitis. It is unclear if oral aloe gel is beneficial in patients with ulcerative colitis. Details: One small clinical trial in patients with mild to moderate ulcerative colitis shows that taking aloe gel for 4 weeks, starting at 25-50 mL twice daily for the first 3 days and increasing to 100 mL twice daily thereafter, reduces symptoms when compared with placebo (11984).
• Vaginitis. It is unclear if topical aloe is beneficial for vaginitis. Details: One small clinical trial in postmenopausal patients with atrophic vaginitis shows that applying 5 mg of a vaginal cream containing aloe gel 2% nightly for 2 weeks, then 3 nights per week for 4 weeks, reduces vaginal dryness, burning, and pain during intercourse and improves measures of vaginal health and maturity when compared to baseline. These effects were similar to those seen with estrogen vaginal cream (104175).
• Varicose veins. Although there has been interest in using oral and topical aloe for varicose veins, there is insufficient reliable information about the clinical effects of aloe for this purpose.
• Wound healing. There is conflicting evidence about the effectiveness of topical aloe products for improving wound healing. These conflicting findings may be due to differences in study designs, products used, and application practices. Details: One small clinical study shows that applying aloe gel to a caesarean wound after surgery, followed by a dry gauze, improves wound healing over the first 24 hours when compared with the dry gauze alone (90128). However, other clinical research in a small number of patients undergoing gynecologic surgery or cesarean section shows that applying an aloe gel extract (Carrington Dermal Wound Gel) to surgical wounds may actually delay wound healing (11982). Another small clinical trial shows that applying a formulation of aloe gel 0.5% cream (Zarband, Phytopharmaceutical Co.) to hemorrhoidectomy wounds three times daily for 4 weeks improves healing rates and pain relief scores and decreases intake of narcotic analgesics when compared with placebo (17418). However, another clinical trial in patients with biopsy wounds shows that application of a hydrogel containing the aloe constituent, acemannan (Carrasyn, Carrington hydrogel), does not improve wound epithelialization, wound infections, or pain when compared with conventional therapy (19856). Additionally, there is contradictory evidence about the effectiveness of aloe for improving skin graft donor site healing. One small clinical study shows that applying aloe gel 87.4% daily to split-thickness skin graft donor sites reduces time to complete healing by about 2 days when compared with placebo (97320). However, another small clinical study shows that applying aloe cream three times daily to split-thickness skin graft donor sites does not improve healing time when compared with placebo (97321).
• Wrinkled skin. Although there has been interest in using topical aloe for wrinkled skin, there is insufficient reliable information about the clinical effects of aloe for this purpose. More evidence is needed to rate aloe for these uses.

(Read more about ALOE)

LIKELY EFFECTIVE

• Copper deficiency. Oral or intravenous copper is beneficial for treatment of copper deficiency. Details: Taking copper orally or intravenously is effective for treating copper deficiency and anemia due to copper deficiency. Copper deficiency is rare. It is seen most commonly in people receiving prolonged parenteral nutrition (7135). Oral cupric sulfate has been used in doses up to 0.1 mg/kg daily (7135). Copper 1-2 mg per day in parenteral nutrition solution has also been used (505).

POSSIBLY INEFFECTIVE

• Alzheimer disease. Oral copper does not seem to be beneficial for Alzheimer disease. Details: Preliminary clinical research shows that taking copper orotate dihydrate, providing 8 mg of elemental copper, daily for 12 months does not improve scores on evaluation scales for Alzheimer disease when compared with placebo (45949). There is also some concern that copper could have detrimental effects. Observational research has found that people with Alzheimer disease have higher levels of copper in their blood than people without the disease (95917); the clinical significance of this finding is unclear.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Oral copper has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a specific combination product containing copper (NicAzel, Elorac Inc.) 1-4 tablets daily for 8 weeks reduces inflammatory lesions in patients with inflammatory acne when compared with baseline. Other ingredients in this product include nicotinamide, azelaic acid, zinc, pyridoxine, and folic acid; specific quantities are not known (90800). The validity of this finding is limited by the lack of a comparator group.
• Brain tumor. It is unclear if oral copper is beneficial for use in glioblastoma. Details: A moderate-sized open-label clinical study in adults with first recurrence of glioblastoma receiving alkylating chemotherapy shows that taking elemental copper 2.5 mg with disulfiram 400 mg daily for 6 months does not improve survival but does result in significantly more adverse effects (e.g., elevated liver enzymes) when compared with control. The trial was stopped early due to safety concerns (112376).
• Cardiovascular disease (CVD). Although there is interest in using oral copper for CVD prevention, there is insufficient reliable information about the clinical effects of copper for this purpose.
• Chemotherapy-induced acral erythema. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 acral erythema (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Chemotherapy-induced anemia. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months does not appear to reduce the incidence of grades 3 and 4 anemia (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Chemotherapy-induced diarrhea. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 diarrhea (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Chemotherapy-induced leukopenia. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months does not appear to reduce the incidence of grades 3 and 4 neutropenia or febrile neutropenia (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Chemotherapy-induced nausea and vomiting (CINV). Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 vomiting (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Chronic venous insufficiency (CVI). It is unclear if compression stockings containing copper are beneficial for lipodermatosclerosis in patients with CVI. Details: Preliminary clinical research shows that using compression stockings impregnated with copper for 8 weeks does not improve overall symptoms of lipodermatosclerosis secondary to chronic venous disease when compared with using a compression stocking without copper. However, the affected surface area may be reduced by approximately 16% by 2 weeks when copper-impregnated compression stockings are used (101809).
• Dental plaque. It is unclear if rinsing the mouth with copper is beneficial for reducing dental plaque. Details: Preliminary clinical research shows that rinsing the mouth with a solution of copper 1.1 mmol/L for 4 days decreases plaque accumulation when compared with a placebo solution (46006).
• Diarrhea. Oral copper has only been evaluated in combination with zinc; its effect when used alone is unclear. Details: Preliminary clinical research in children 6 months to 5 years of age presenting to a hospital in India with acute watery or bloody diarrhea shows that taking a solution providing zinc 2 mg/kg and copper 0.2 mg/kg orally daily for 2 weeks does not reduce the duration of diarrhea, the weight of stool, or the need for rehydration when compared with placebo (87166). It also does not seem to reduce the recurrence of diarrhea or improve weight gain over the next 3 months (95540).
• Oral mucositis. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 oral mucositis (112377). However, the interpretation of these findings is limited by the lack of a control group.
• Osteoarthritis. Although there is interest in using topical copper for osteoarthritis, there is insufficient reliable information about the clinical effects of copper for this condition.
• Osteoporosis. Oral copper has only been evaluated in combination with other minerals; its effect when used alone is unclear. Details: Preliminary clinical research in postmenopausal adults shows that taking copper 2.5 mg in combination with zinc 15 mg, manganese 5 mg, and calcium 1000 mg daily for 2 years can slow bone loss when compared with taking either calcium or the trace minerals alone (1994).
• Postoperative infection. It is unclear if copper-impregnated wound dressings are beneficial for the prevention of postoperative infection. Details: Preliminary clinical research shows that using a wound dressing impregnated with copper oxide 3% by weight reduces the incidence of a surgical site infection in the 30-day period following a caesarean section by 39%, but does not reduce length of hospital stay or readmission rate, when compared with a non-copper wound dressing. Eight patients would need to be treated with the copper-impregnated dressing to prevent one infection (105363). This study is limited by the use of a telephone questionnaire to assess the suspicion of infection.
• Systemic lupus erythematosus (SLE). It is unclear if oral copper is beneficial for improving symptoms of SLE. Details: Copper status does not appear to be associated with the risk of SLE (101810). Additionally, one small clinical study shows that taking copper 3 mg daily, alone or in combination with fish oil, for 24 weeks does not affect symptoms of SLE when compared with placebo (12953).
• Tinea pedis. Although there is interest in using topical copper for tinea pedis, there is insufficient reliable information about the clinical effects of copper for this condition.
• Wound healing. It is unclear if topical copper sulfate can improve the healing of umbilical granuloma. Details: A small clinical study in children 1-3 months of age with treatment-naïve umbilical granuloma shows that a single application of copper sulfate to the affected site results in complete resolution in 70% of patients, compared with 90% of patients receiving topical sodium chloride twice daily for 5 days. Some patients who received a second application of copper sulfate experienced full healing; however, it is unclear if this was due to the treatment or natural resolution (109403). More evidence is needed to rate copper for these uses.

(Read more about COPPER)

EFFECTIVE

• Sunburn. Topical PABA prevents sunburn. Details: PABA is an FDA-approved sunscreen (266,8952). PABA seems to be effective during sweating, but not when skin is immersed in water (272). PABA sunscreens can be applied topically in concentrations of 1% to 15% (272).

POSSIBLY EFFECTIVE

• Peyronie disease. Low quality clinical research shows that oral PABA improves Peyronie disease symptoms. Details: PABA is FDA-approved for use in this condition. Clinical research shows that taking the specific PABA product (POTABA, Glenwood LLC.), 3 grams orally four times a day for 8-12 months can reduce penile curvature and deterioration when compared with placebo (1067,8951,67982).

POSSIBLY INEFFECTIVE

• Scleroderma. Clinical research is conflicting, but suggests that oral PABA is not effective for treating scleroderma. Details: Although PABA is FDA-approved for scleroderma, as well as morphea, a localized form of scleroderma, evidence supporting its use is limited. Some retrospective studies suggest it might help for some symptoms of scleroderma, but higher quality evidence shows that it is not beneficial (1071,1073,1074,1075).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging skin. Although there has been interest in using oral PABA for aging skin, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Constipation. Although there has been interest in using oral PABA for constipation, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Headache. Although there has been interest in using oral PABA for headache, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Herpes keratitis. Although there has been interest in using ophthalmic PABA for herpes keratitis, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Infertility. Although there has been interest in using oral PABA for infertility, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Inflammatory myopathies. It is unclear if oral PABA is beneficial in patients with inflammatory myopathies. Details: PABA is FDA-approved for use in dermatomyositis, a type of inflammatory myopathy, but there is limited evidence to support this use (10). PABA is taken as 12 grams orally daily in 4 to 6 divided doses in adults or 220 mg/kg orally daily in 4 to 6 divided doses in children (10).
• Pemphigus. It is unclear if oral PABA is beneficial in patients with pemphigus. Details: PABA is FDA-approved for use in pemphigus, but there is limited evidence to support this use (10). PABA is taken as 12 grams orally daily in 4 to 6 divided doses in adults or 220 mg/kg orally daily in 4 to 6 divided doses in children (10).
• Systemic lupus erythematosus (SLE). Although there has been interest in using oral PABA for SLE, there is insufficient reliable information about the clinical effects of PABA for this purpose.
• Vitiligo. Although there has been interest in using oral PABA for vitiligo, there is insufficient reliable information about the clinical effects of PABA for this purpose. More evidence is needed to rate PABA for these uses.

(Read more about PARA-AMINOBENZOIC ACID (PABA))

EFFECTIVE

• Phenylketonuria (PKU). Oral tyrosine as a component of medical foods is recommended in people with PKU, a disorder in which phenylalanine cannot be endogenously metabolized into tyrosine. Details: Tyrosine is used as a component of medical foods for people with phenylketonuria (PKU) (7212,7213,7232). Current guidelines recommend that people with PKU maintain a diet low in phenylalanine and incorporate tyrosine as a component of medical foods to maintain normal blood levels of tyrosine (95108). Supplementation with additional tyrosine is recommended only for patients with consistently low blood levels of tyrosine despite using tyrosine-containing medical foods (95108). Routine supplementation with free tyrosine is not recommended for most patients because it can produce wide variations in tyrosine plasma concentrations and side effects (7212,95108). Tyrosine intake does not improve neuropsychological measures in patients with PKU (81503,91471,95108).

POSSIBLY EFFECTIVE

• Cognitive function. Oral tyrosine might improve cognitive function, particularly in patients exposed to stressors such as excessive cold, noise, or sleep deprivation. Details: Most research suggests that taking tyrosine orally improves cognitive function, particularly under stressful conditions. Small clinical studies in healthy adults show that taking tyrosine 100-300 mg/kg in the setting of exposure to stressors such as excessive cold, noise, or sleep deprivation improves cognitive performance measures, such as executive function and short-term memory, when compared with placebo (7215,81472,81476,81484,81501). Other small clinical studies in healthy patients show that taking tyrosine 2 grams may improve response time without detracting from performance and could improve some measures of cognitive response to conflict when compared with placebo (101082,111248). Some of these small studies may be inadequately powered to detect an effect on some cognitive function tests. Tyrosine has also been evaluated in combination with other ingredients for this purpose. A small clinical study in healthy adults with fatigue shows that taking tyrosine, serine, alanine, glutamate, and aspartate daily for 4 weeks improves measures of cognitive function including attention, spatial cognition, orientation, motivation, and time management when compared with placebo (111249). It is unclear if these effects are due to tyrosine, other ingredients, or the combination.
• Memory. Taking tyrosine orally seems to improve memory in patients exposed to stressors such as cold or those having to complete multiple tasks at once. Details: Small clinical studies in healthy adults show that taking tyrosine 150-300 mg/kg prior to acute exposure to stress that is cold-induced, noise-induced, or induced by multi-tasking improves memory performance when compared with placebo (81469,81477,81499,81501). However, tyrosine 150 mg/kg does not seem to improve memory in less stressful situations such as performing one simple task or testing when not exposed to cold (81469,81499).

POSSIBLY INEFFECTIVE

• Athletic performance. Oral tyrosine does not improve athletic performance when taken prior to exercise. Details: Clinical studies show that taking tyrosine orally prior to participating in treadmill or cycling exercises conducted at temperate temperatures or in the heat does not improve strength, endurance, or performance when compared with placebo (81471,81474,81504,91470,104403). Another very small clinical study in healthy males shows that taking a multi-ingredient pre-workout supplement containing L-tyrosine, beta-alanine, L-citrulline maleate, arginine alpha-ketoglutarate, L-taurine, and caffeine does not increase bench press strength endurance when compared with equivalent amounts of anhydrous caffeine (111250).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alcohol use disorder. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with alcohol use disorder shows that taking a combination of tyrosine 900 mg, D,L-phenylalanine 1.5 grams, L-glutamine 300 mg, and L-tryptophan 400 mg daily along with a multivitamin supplement reduces withdrawal symptoms and decreases stress when compared with placebo (81552). It is unclear if these effects are due to tyrosine, other ingredients, or the combination.
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral tyrosine is beneficial for improving ADHD symptoms. Details: A very small clinical study shows that taking tyrosine does not improve symptoms of ADHD in children when compared with baseline (7209). Furthermore, another very small clinical trial in adults with ADHD shows that taking tyrosine daily for 8 weeks does not improve inattention when compared with baseline. Some patients might have transient symptom improvement after 2 weeks, but seem to acquire tolerance by 6 weeks (7210). The validity of these findings is limited by the small study size and lack of control groups.
• Cocaine dependence. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with cocaine dependence shows that taking L-tyrosine 1 gram in the morning and L-tryptophan 1 gram in the evening for 14 days does not reduce drug cravings or withdrawal symptoms when compared with placebo (81480).
• Dementia. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in patients with severe Alzheimer disease or multi-infarct dementia shows that taking a combination of tyrosine 4 grams, 5-HTP 800 mg, and carbidopa 100 mg orally daily does not improve clinical or psychological parameters in most patients when compared with baseline (918). The validity of this finding is limited by the small study size and a lack of control group.
• Depression. It is unclear if oral tyrosine is beneficial for improving major depressive disorder. Details: A small clinical study in patients with major depression shows that taking L-tyrosine 100 mg/kg daily for 4 weeks does not improve depressive symptoms when compared with placebo (7208).
• Erectile dysfunction (ED). Although there is interest in using oral tyrosine for ED, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Fatigue. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy adults with fatigue shows that taking tyrosine, serine, alanine, glutamate, and aspartate daily for 4 weeks does not improve subjective or objective measures of fatigue when compared with placebo (111249).
• Hypertension. It is unclear if oral tyrosine is beneficial for reducing hypertension of mild severity. Details: A very small clinical study in patients with mild essential hypertension shows that taking oral tyrosine 2.5 grams three times daily with meals for 2 weeks does not affect systolic or diastolic blood pressure when compared with control (81487).
• Mitochondrial myopathies. Although there is interest in using oral tyrosine for nemaline myopathy, a type of mitochondrial myopathy, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Narcolepsy. It is unclear if oral tyrosine is beneficial for improving narcolepsy symptoms. Details: A small clinical study in patients with narcolepsy shows that taking capsules containing tyrosine 3 grams orally three times daily for 4 weeks might reduce feelings of tiredness or drowsiness when compared with placebo, but the overall effect is not clinically significant. Tyrosine also does not seem to improve sudden muscle weakness, sleep paralysis, night-time sleep, sleep latency, or speed and attention after waking when compared with placebo (81482).
• Obesity. Oral tyrosine has only been evaluated for in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in overweight or obese patients shows that taking a supplement containing tyrosine 1.2 grams, cayenne 450 mg, green tea 1.5 grams, caffeine 150 mg, and calcium carbonate 3.89 grams daily for 8 weeks slightly reduces body fat mass by 0.9 kg when compared with placebo (81475). It is not clear if any potential benefit is due to tyrosine, other ingredients, or the combination.
• Opioid withdrawal. Oral tyrosine has only been evaluated for heroin withdrawal in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in Chinese males undergoing detoxification for heroin addiction shows that taking a combination of tyrosine 50 mg/kg, 5-HTP 200 mg, phosphatidylcholine 1200 mg, and L-glutamine 50 mg/kg daily for 6 days can reduce insomnia and withdrawal symptoms and improve mood when compared with placebo (88178). It is not clear if this effect is due to tyrosine, other ingredients, or the combination.
• Parkinson disease. Although there is interest in using oral tyrosine for Parkinson disease, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Premenstrual syndrome (PMS). Although there is interest in using oral tyrosine for PMS, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Schizophrenia. It is unclear if oral tyrosine is beneficial for improving schizophrenia symptoms. Details: A very small clinical study in patients with schizophrenia shows that taking L-tyrosine 10 grams daily in four divided doses along with molindone 150 mg daily for 3 weeks does not improve symptoms of schizophrenia when compared with taking molindone alone (81554).
• Sleep deprivation. It is unclear if oral tyrosine is beneficial for improving alertness in sleep deprived adults. Details: A small clinical study shows that taking tyrosine 150 mg/kg after the loss of a night's sleep seems to delay performance decline in psychomotor tests by about 3 hours when compared with placebo (7215). Another small clinical study in sleep-deprived patients shows that taking tyrosine 150 mg/kg improves memory, reasoning, and vigilance when compared with placebo at 5.5 hours after ingestion, but not at 1.5 hours. Tyrosine was less effective than taking amphetamine, phentermine, or caffeine (81472).
• Stress. Although there is interest in using oral tyrosine for stress, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Wrinkled skin. Topical tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small study in patients with photodamaged skin shows that applying a topical preparation containing 10% vitamin C, acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (High Potency Serum, Cellex-C International Inc.) for 3 months to the face seems to improve fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the benefits are due to tyrosine, other ingredients, or the combination. More evidence is needed to rate the effectiveness of tyrosine for these uses.

(Read more about TYROSINE)

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.
• Cataracts. Dietary and supplemental intake of vitamin C may reduce the risk of developing cataracts. Details: Population research suggests 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, with the most benefit observed for nuclear cataracts (96711). Additionally, another observational study shows that higher supplemental intake of vitamin C over 10 years is associated with a 60% reduction in the incidence of nuclear and cortical cataracts (4208). Other population research suggests that individuals with the highest blood levels of vitamin C have a 33% lower odds of developing age-related cataract, but any benefit is limited to Asian populations (90944). An umbrella review of meta-analyses also shows that dietary intake of vitamin C is associated with a 27% lower odds of cataract development (112095). However, a prospective clinical study shows that a combination of vitamin C, vitamin E, and beta-carotene does not prevent age-related loss of vision from cataracts in well-nourished people with an average supplementation duration of 6.3 years (7304).
• Common cold. Oral high-dose vitamin C might modestly shorten and 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 in healthy children and adults shows that taking vitamin C 1-4 grams daily for one week to 5 months reduces cold severity by 13%, limits absences from daily activities, and improves the duration of severe symptoms, but does not reduce the duration of mild symptoms, when compared with placebo (113665). Vitamin C has also been investigated for preventing the common cold. 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, but some evidence is conflicting. Details: Vitamin C seems to modestly reduce systolic blood pressure (SBP), without meaningful effects on diastolic blood pressure (DBP) (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 SBP but not DBP 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 SBP 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 SBP by about 4 mmHg and DBP 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. In contrast, a network meta-analysis of small, low-quality clinical studies comparing five different vitamins in adults with essential hypertension shows that vitamin C does not reduce SBP, DBP, mean 24-hour SBP, mean 24-hour DBP, or heart rate when compared with placebo and when indirectly compared with vitamin B2, vitamin D, vitamin E, and folic acid. However, the included studies were of low quality and high heterogeneity, particularly in dosing, limiting the validity of the results (113668).
• 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). For dental surgery, a small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces pain 24, 48, and 72 hours after surgery when compared with control (113664). 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).
• 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). However, another large epidemiological cancer screening trial with a mean follow-up of over 12 years suggests that moderate dietary intake of vitamin C around 500 mg daily is protective against lung cancer, but higher doses of vitamin C might increase the risk of lung cancer (112096).
• 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

• 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. Most studies show that oral or intravenous vitamin C given to patients hospitalized with COVID-19 does not improve organ function or survival, but the evidence is conflicting. It is unclear whether vitamin C is beneficial for long COVID. 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. A very large analysis of two multinational clinical studies in critical and non-critical adults hospitalized with COVID-19 shows that administering intravenous vitamin C 50 mg/kg every 6 hours for 96 hours does not improve organ support-free days or survival and has a high probability of futility and worsened outcomes when compared with placebo (113666). 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). However, a meta-analysis and some small individual studies have found that vitamin C is modestly beneficial for patients hospitalized with COVID-19. 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). Similarly, a meta-analysis of 8 clinical studies in primarily hospitalized patients with moderate to severe COVID-19 shows that vitamin C administered orally or intravenously decreases the risk of all-cause mortality by 16% when compared with control (114488). Additionally, a small study found a small improvement in survival when compared with standard care; however, the overall survival rate in this study was low (108075). Another 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. Vitamin C has also been evaluated in combination with other ingredients 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). However, it is unclear whether these effects are due to vitamin C, L-arginine, or the combination.
• 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, three randomized clinical trials in patients with sepsis or septic shock show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027,114489). A small clinical study in patients with septic shock shows that intravenous vitamin C 50 or 150 mg/kg daily for 4 days does not improve organ dysfunction or failure rates, duration of hospital or intensive care unit (ICU) length of stay, duration of mechanical ventilation, or mortality rate when compared with placebo (114489). Another 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 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. Four meta-analyses of randomized controlled trials and observational studies show that intravenous vitamin C does not have a significant effect on the length of hospital stay, mortality at 1 month, ICU mortality, use of invasive ventilation, use of renal replacement therapy, organ function, or incidence of kidney injury when compared with placebo or standard care. The meta-analyses reach conflicting conclusions on whether intravenous vitamin C reduces the risk of in-hospital mortality, 30-day mortality, and the duration of ICU stay. When only data from low risk-of-bias clinical trials are considered, the effects of intravenous vitamin C on mortality at any point are no longer significant (106933,106934,109957,113663). However, 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). It is unclear if dietary vitamin C or oral vitamin C taken in combination with other ingredients prevents AMD. Details: An umbrella review of meta-analyses shows that increased dietary intake of vitamin C is associated with 21% higher odds of developing AMD (112095). A population study suggests that vitamin C intake is associated with increased odds of developing age-related maculopathy (9823). However, other population studies have found no association between dietary or supplemental vitamin C intake and the risk of developing AMD (14007,14257). When taken in combination with other ingredients, most clinical and population research shows that taking vitamin C 500 mg along with other antioxidants such as vitamin E 400 IU, beta-carotene 15 mg, and/or elemental zinc 80 mg reduces the risk of visual acuity loss by 23% to 27%, progression to advanced AMD at 5 years by 25% to 32%, and AMD overall (7303,7304,11326,14257,90069). 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). 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).
• Cardiac arrest. It is unclear if intravenous vitamin C is beneficial for patients after cardiac arrest. Details: A small clinical study conducted in Slovenia in adult survivors of out-of-hospital cardiac arrest shows that administering intravenous vitamin C 1.5 grams every 12 hours for 8 consecutive doses, with the first dose administered within 6 hours of resuscitation, in addition to standard care protects against arrhythmias and reduces the length of intensive care unit (ICU) stay when compared with placebo and standard care. However, intravenous vitamin C does not appear to protect against neurological or myocardial injury, reduce the need for mechanical ventilation, reduce the duration of hospital stay, or increase survival when compared with placebo (113667).
• 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.
• 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).
• Child growth. Some clinical research in pregnant smokers suggests that taking vitamin C during pregnancy may improve pulmonary function in the offspring from birth to 6 years of age. Details: A meta-analysis of 4 data sets from one large clinical study in pregnant adults who smoke at least one cigarette daily shows that taking supplemental vitamin C 500 mg daily during pregnancy reduces lower airway resistance and improves lung capacity of the offspring at 0, 3, 12, and 60 months of age, but does not improve airway obstruction, when compared with control (113670). Additionally, one of the clinical studies included the meta-analysis shows that taking vitamin C during pregnancy lowers the occurrence of wheezing in offspring at 4-6 years of age (114496,114497).
• 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). Additionally, a meta-analysis of 4 other, mostly small clinical studies in patients with endometriosis shows that taking vitamin C 1000 mg and vitamin E 800-1200 IU daily for 6-8 weeks reduces chronic pelvic pain and improves dysmenorrhea and dyspareunia when compared with placebo (114491).
• 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 to baseline (14018). The validity of these findings is limited by the small study size and lack of a comparator group. However, a very large observational study suggests that there is no association between dietary vitamin C intake and in-vitro fertilization (IVF) outcomes including good oocyte quality, embryo transfer success rates, clinical pregnancy rates, and successful term pregnancy rates in subfertile couples who are candidates for IVF (112097).
• 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 or intravenous vitamin C helps to prevent or treat pneumonia. Details: A meta-analysis of 6 clinical studies in adults with community-acquired pneumonia shows that oral or intravenous vitamin C does not reduce overall mortality, hospital or intensive care unit length of stay, or the risk of mechanical ventilation when compared with control (114490). The interpretation of these results is limited by significant heterogeneity of the included studies. An earlier meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the risk of pneumonia when compared with a 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 unit (ICU) or hospital stay with vitamin C supplementation (96705), while another clinical study in patients undergoing cardiac surgery with extracorporeal circulation shows that intravenous vitamin C administered during surgery and 48 hours after surgery reduces ICU stay and re-admission rates, wound infection, and hospital mortality, but not length of hospital stay, when compared with control (114492). 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).
• Postoperative pulmonary complications. It is unclear if intravenous vitamin C improves postoperative pulmonary complications. Details: A large, single-blind clinical study in patients with recent cardiac surgery with extracorporeal circulation shows that parenteral administration of vitamin C 50 mg/kg intraoperatively and 50 mg/kg every 6 hours for the next 48 hours, followed by oral vitamin C 2000 mg daily until 1-week post-discharge, reduces the incidence of postoperative pulmonary complications (PPC) by 22% and improves PPC severity scores when compared with control. Specifically, vitamin C reduces the incidence of pneumothorax, pleural effusion, pneumonia, and re-intubation and may ameliorate lung damage as suggested by higher Horowitz index when compared with control (114492). A small clinical trial in patients undergoing low-risk cardiac surgery 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).
• Postoperative swelling. It is unclear if vitamin C reduces postoperative swelling after dental surgery. Details: A small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces swelling 7 days after surgery when compared with control. However, vitamin C does not seem to reduce swelling 3 days after surgery when compared with control, suggesting that longer durations are needed for anti-inflammatory effects (113664).
• 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). Another meta-analysis of clinical research shows that taking vitamin C during pregnancy decreases the risk of PROM by 43% and preterm PROM by 33%, but does not decrease the risk of term PROM, when compared with a control. While vitamin C was studied in doses of 100, 500, and 1000 mg daily, the decreased risk of PROM was only observed in studies of 100 mg daily (114493). A moderate-sized 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). Additionally, a meta-analysis of observational studies suggests that vitamin C levels in the blood tend to be lower in patients with PROM, particularly preterm PROM (114493). 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)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Bleeding. Although there has been interest in using topical yucca for bleeding, there is insufficient reliable information about the clinical effects of yucca for this purpose.
• Dandruff. Although there has been interest in using topical yucca for dandruff, there is insufficient reliable information about the clinical effects of yucca for this purpose.
• Diabetes. Although there has been interest in using oral yucca for diabetes, there is insufficient reliable information about the clinical effects of yucca for this purpose.
• Hypercholesterolemia. Oral yucca has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with hypercholesterolemia shows that taking purified yucca extract in combination with quillaia extract orally three times daily for 4 weeks decreases total and low-density lipoprotein (LDL) cholesterol levels by more than 10% and 15%, respectively, when compared with baseline (86899). The validity of this finding is limited by the lack of statistical comparison to the placebo group.
• Hypertension. Although there has been interest in using oral yucca for hypertension, there is insufficient reliable information about the clinical effects of yucca for this purpose.
• Joint pain. Although there has been interest in using topical yucca for joint pain, there is insufficient reliable information about the clinical effects of yucca for this purpose.
• Migraine headache. Although there has been interest in using oral yucca for migraine headache, there is insufficient reliable information about the clinical effects of yucca for this purpose. More evidence is needed to rate yucca for these uses.

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LIKELY SAFE ...when aloe gel is used topically and appropriately. Aloe gel-containing formulations have been safely applied in clinical trials (101,11982,12096,12098,12159,12160,12163,12164,17418)(90123,90124,90127,90128,90129,90131,97320,98816,103305). When included in topical cosmetics, the Cosmetic Ingredient Review Expert Panel concluded that aloe-derived anthraquinone levels should not exceed 50 ppm (90122).

POSSIBLY SAFE ...when aloe gel is used orally and appropriately, short-term. Aloe gel has been safely used in a dose of 15 mL daily for up to 42 days or 100 mL of a 50% solution twice daily for up to 4 weeks (11984,12164). Also, a specific aloe gel complex (Aloe QDM complex, Univera Inc.) has been safely used at a dose of approximately 600 mg daily for up to 8 weeks (90121). ...when aloe extract is used orally and appropriately, short-term. Aloe extract has been used with apparent safety in a dose of 500 mg daily for one month (101579). Also, an aloe extract enriched in aloe sterols has been used with apparent safety in a dose of 500 mg daily for 12 weeks (101577).

POSSIBLY UNSAFE ...when aloe latex is used orally. There is some evidence that anthraquinones in aloe latex are carcinogenic or promote tumor growth, although data are conflicting (6138,16387,16388,91596,91597). In 2002, the US FDA banned the use of aloe latex in laxative products due to the lack of safety data (8229). ...when aloe whole-leaf extract is used orally. Aloe whole-leaf extract that has not been filtered over charcoal still contains anthraquinones. This type of aloe whole-leaf extract is referred to as being "nondecolorized". The International Agency for Research on Cancer has classified this type of aloe whole-leaf extract as a possible human carcinogen (91598,91908). Although filtering aloe whole-leaf extract over charcoal removes the anthraquinones, some animal research suggests that this filtered extract, which is referred to as being "decolorized", may still cause gene mutations (91598). This suggests that constituents besides anthraquinones may be responsible for the carcinogenicity of aloe whole-leaf extract. It should be noted that commercial products that contain aloe whole-leaf extract may be labeled as containing "whole leaf Aloe vera juice" or "aloe juice" (91908).

LIKELY UNSAFE ...when aloe latex is used orally in high doses. Ingesting aloe latex 1 gram daily for several days can cause nephritis, acute kidney failure, and death (8,8961).

CHILDREN: POSSIBLY SAFE
when aloe gel is used topically and appropriately. Aloe gel-containing formulations have been safely applied in clinical trials (90124,90131).

CHILDREN: POSSIBLY UNSAFE
when aloe latex and aloe whole leaf extracts are used orally in children. Children younger than 12 years may experience abdominal pain, cramps, and diarrhea (4).

PREGNANCY: POSSIBLY UNSAFE
when used orally. Anthraquinones present in aloe latex and aloe whole leaf extracts have irritant, cathartic, and possible mutagenic effects (4,16387,16388,90122). There are also anecdotal reports and evidence from animal research that anthraquinones or aloe whole leaf extracts might induce abortion and stimulate menstruation; avoid using (4,8,19,90122).

LACTATION: POSSIBLY UNSAFE
when aloe preparations are used orally. Cathartic and mutagenic anthraquinones present in aloe latex and aloe whole leaf extracts might pass into milk; avoid using (4,19).

(Read more about ALOE)

LIKELY SAFE ...when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 10 mg daily (7135).

POSSIBLY SAFE ...when copper oxide is used topically. A wound dressing impregnated with copper oxide in concentrations of 3% by weight has been used with apparent safety in one clinical trial (105363).

POSSIBLY UNSAFE ...when used orally in doses exceeding the UL of 10 mg daily. Higher intake can cause liver damage (7135,45865). Kidney failure and death can occur with ingestion of as little as 1 gram of copper sulfate (17).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 1 mg daily for 1-3 years of age, 3 mg daily for 4-8 years of age, 5 mg daily for 9-13 years of age, and 8 mg daily for 14-18 years of age (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in doses exceeding the UL (7135). Higher intake can cause liver damage (7135).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 8 mg daily for those 14-18 years of age or 10 mg daily for those 19 years and older (7135).

PREGNANCY: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher intake can cause liver damage (7135).

LACTATION: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 8 mg daily for those 14-18 years of age or 10 mg daily for those 19 years and older (7135).

LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher intake can cause liver damage (7135).

(Read more about COPPER)

LIKELY SAFE ...when used topically and appropriately. PABA is FDA approved for topical use and there have not been reports of significant toxicity (266,272).

POSSIBLY SAFE ...when used orally and appropriately (10). PABA is an FDA-approved drug, but some potentially serious side effects have been reported (10).

POSSIBLY UNSAFE ...when used orally in high doses. Doses greater than 12 grams per day have been associated with leukopenia (1061).

CHILDREN: LIKELY SAFE
when used topically and appropriately (266,272).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately (10). PABA is an FDA-approved drug for use in children, but serious side effects have been reported (10).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Doses greater than 220 mg/kg/day have been associated with fatal toxic effects (1061).

PREGNANCY AND LACTATION: LIKELY SAFE
when used topically and appropriately (266,272). There is insufficient reliable information available about the safety of the oral use of PABA during pregnancy and breast-feeding; avoid using.

(Read more about PARA-AMINOBENZOIC ACID (PABA))

LIKELY SAFE ...when used orally in amounts commonly found in foods. Tyrosine has Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts, short-term. Tyrosine has been used safely in doses up to 150 mg/kg daily for up to 3 months (7210,7211,7215). ...when used topically and appropriately (6155).

PREGNANCY AND LACTATION:
There is insufficient reliable information available about the safety of tyrosine during pregnancy and lactation when used in medicinal amounts. Some pharmacokinetic research shows that taking a single dose of tyrosine 2-10 grams orally can modestly increase levels of free tyrosine in breast milk. However, total levels are not affected, and levels remain within the range found in infant formulas. Therefore, it is not clear if the increase in free tyrosine is a concern (91467).

(Read more about TYROSINE)

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) and has been used with apparent safety in clinical trials up to 150 mg/kg daily for up to 4 days (114489) and up to 200 mg/kg daily for up to 2 days (114492).

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 used orally in amounts commonly found in foods. Specific species of yucca, including Mojave yucca (Yucca shidigera) and Joshua tree (Yucca brevifolia), have Generally Recognized As Safe (GRAS) status for use in foods in the US (4912). There is insufficient reliable information available about the safety of yucca when used orally as medicine or when applied topically.

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

(Read more about YUCCA)

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, aloe gel might increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs.  Details In vitro research shows that aloe gel can inhibit platelet aggregation. This inhibition was greater than that seen with celecoxib, but less than that seen with aspirin (105501).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Aloe might increase the risk of hypoglycemia when taken with antidiabetes drugs.  Details Preliminary clinical research suggests aloe gel might lower blood glucose levels (11983,12164,19756) and have additive effects when used with antidiabetes drugs. Monitor blood glucose levels closely.

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, aloe might decrease the levels and clinical effects of CYP1A2 substrates.  Details In vitro research shows that aloe extract induces CYP1A2 enzymes (111404).

DIGOXIN (Lanoxin) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Theoretically, aloe latex might increase the risk of adverse effects when taken with cardiac glycosides.  Details Overuse of aloe latex can increase the risk of adverse effects from cardiac glycoside drugs, such as digoxin, due to potassium depletion. Overuse of aloe, along with cardiac glycoside drugs, can increase the risk of toxicity (19).

DIURETIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, aloe latex might increase the risk of hypokalemia when taken with diuretic drugs.  Details Overuse of aloe latex might compound diuretic-induced potassium loss, increasing the risk of hypokalemia (19).

STIMULANT LAXATIVES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, aloe latex might increase the risk for fluid and electrolyte loss when taken with stimulant laxatives.  Details Due to cathartic laxative effects of aloe latex, concomitant use with other stimulant laxatives might compound fluid and electrolyte loss (19,19742,19743,19744).

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, aloe latex might increase the risk of bleeding when taken with warfarin.  Details Aloe latex has stimulant laxative effects. In some people aloe latex can cause diarrhea. Diarrhea can increase the effects of warfarin, increase international normalized ratio (INR), and increase the risk of bleeding. Advise patients who take warfarin not to take excessive amounts of aloe vera.

(Read more about ALOE)

CONTRACEPTIVE DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking copper with contraceptive drugs might increase the levels and toxic effects of copper.  Details A meta-analysis of clinical studies suggests that chronic use of oral contraceptives increases serum copper levels by a mean of 57 mcg/dL. In most people, this resulted in levels above the normal reference range for copper (92395).

PENICILLAMINE (Cuprimine, Depen) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, taking copper with penicillamine might decrease the absorption of penicillamine; separate dosing by at least 2 hours.  Details Copper chelates penicillamine, which decreases its absorption and may reduce its clinical effects (4412,4453,4531,4535,9630).

(Read more about COPPER)

CORTISONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, concomitant use of PABA and cortisone may increase the effects of cortisone.  Details Preliminary clinical research shows that PABA decreases the metabolism of cortisone (4488). Dose adjustments of cortisone may be necessary.

DAPSONE (Avlosulfon) Interaction Rating = Major Do not take this combination. Severity = Moderate •  Occurrence = Likely •  Level of Evidence = D Theoretically, concomitant use of PABA and dapsone may decrease the effects of dapsone.  Details Preliminary clinical research shows that PABA inhibits the antibacterial effects of dapsone (4488). Avoid concurrent use (266).

SULFONAMIDE ANTIBIOTICS Interaction Rating = Major Do not take this combination. Severity = Moderate •  Occurrence = Likely •  Level of Evidence = D Theoretically, concomitant use of PABA and sulfonamide antibiotics inhibits the antibacterial effects of sulfonamide.  Details Sulfonamide antibiotics competitively inhibit folic acid synthesis from PABA. Excess PABA may overcome the folate depleting effect of the sulfonamides (10). Avoid concurrent use.

(Read more about PARA-AMINOBENZOIC ACID (PABA))

LEVODOPA Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, tyrosine might decrease the effectiveness of levodopa.  Details Tyrosine and levodopa compete for absorption in the proximal duodenum by the large neutral amino acid (LNAA) transport system (2719). Advise patients to separate doses of tyrosine and levodopa by at least 2 hours.

THYROID HORMONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, tyrosine might have additive effects with thyroid hormone medications.  Details Tyrosine is a precursor to thyroxine and might increase levels of thyroid hormones (7212).

(Read more about TYROSINE)

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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General ...Orally and topically, aloe products are generally well tolerated when used in typical doses. However, oral aloe latex is associated with a greater risk of adverse effects, especially when used in high doses or long-term.
Most Common Adverse Effects:
Orally: Aloe latex may cause abdominal pain, cramps, and diarrhea.
Topically: Burning, erythema, and itching. Contact dermatitis in sensitive individuals.
Serious Adverse Effects (Rare):
Orally: Aloe latex is associated with serious adverse effects when taken in high doses or long-term. Cases of acute hepatitis due to a hypersensitivity reaction to aloe leaf extract has been reported.

Dermatologic ...Topically, aloe gel has occasionally been associated with burning (12164,19741,30697,30706), itching (12164,19741,30697), eczema (90122), erythema (19748,30706,90123), contact dermatitis (12163,12164,30695,30736,30737,30738,30740), popular eruption (30732), and urticaria (30712). Also, a case of generalized nummular and popular dermatitis attributed to hypersensitivity has been reported for a 47-year-old male who used aloe leaf gel, both topically and orally, for 4 years (30740).

Endocrine ...A case of severe hypokalemia has been reported for a male breast cancer patient who was undergoing chemotherapy and using aloe vera 1 liter daily orally for 2 weeks. The hypokalemia was attributed to the cathartic effects of aloe and resolved once aloe use was discontinued (30704).

Gastrointestinal ...Orally, aloe latex can cause abdominal pain and cramps. Long-term use or abuse of aloe latex can cause diarrhea, sometimes with hypokalemia, albuminuria, hematuria, muscle weakness, weight loss, arrhythmia, and pseudomelanosis coli (pigment spots in intestinal mucosa). Pseudomelanosis coli is believed to be harmless, and usually reverses with discontinuation of aloe. It is not directly associated with an increased risk of developing colorectal adenoma or carcinoma (6138). Orally, aloe gel may cause nausea, stomach cramps, and other gastrointestinal complaints in some patients (104174,111921,111663).
Topically, applying aloe gel in the mouth may cause nausea within 5 minutes of application in some patients (90124).

Hematologic ...A case of Henoch-Schonlein purpura, characterized by abdominal pain, purpura, and severe arthralgia, has been reported in a 52-year-old male who drank aloe juice prepared from four to five leaflets for 10 days prior to symptom development (91598).

Hepatic ...Cases of acute hepatitis have been reported after ingestion of aloe leaf extracts for between 3 weeks and 5 years. This is thought to be a hypersensitivity reaction (15567,15569,16386,17419,90126,91598). A case of acute hepatitis has also been reported for a 45-year-old female who drank two ounces of Euforia juice (Nuverus International), a product containing green tea, noni, goji, and aloe, daily for one month (90125). However, one small clinical trial in healthy individuals shows that taking aloe gel 2 ounces twice daily for 60 days does not impair liver function (104174).

Renal ...Orally, aloe latex can cause hemorrhagic gastritis, nephritis, and acute kidney failure following prolonged use of high doses (1 gram daily or more) (8961).

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General ...Orally, copper is generally well tolerated when consumed in doses below the tolerable upper intake level (UL).

Dermatologic ...Contact dermatitis caused by copper has been reported rarely. A case report describes a 5-year-old male who developed recurrent fingertip dermatitis and a positive skin test to copper after playing with toy cars made with a copper-containing alloy (95538). Also, in a small clinical trial in children 1-3 months of age with umbilical granuloma, 3 of 33 children receiving a single topical application of copper sulfate developed superficial burns, whereas no superficial burns occurred in those receiving topical sodium chloride (109403).
In one case report, a 68-year-old male with type 2 diabetes and peripheral neuropathy developed second- and third-degree burns after wearing a copper-containing compression sock on the right leg for 3 hours while sitting in the sun. The patient received treatment with topical silver sulfadiazine and oral clindamycin. After 6 weeks, the patient was found to have multiple persistent wounds containing necrotic tissue which required debridement, daily dressing changes, and tubular compression. It is thought that the heat conductance of copper magnified the effects of sun exposure in this case (109402).

Endocrine ...There is evidence from observational studies that people with diabetes (type 1 or type 2) have higher copper levels in their blood than people without diabetes, although not all studies have shown this (95537). It is not known if elevated copper levels contribute to development or worsening of diabetes.

Hematologic ...A case report of copper overdose in a 28-year-old male resulted in hemolysis exacerbated by glucose-6-phosphate dehydrogenase deficiency. The patient was hospitalized, received D-penicillamine chelation, blood transfusion, and ultimately, 4 cycles of plasmapheresis which led to clinical recovery (112378).

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General ...Orally and topically, PABA is generally well tolerated.
Most Common Adverse Effects:
Orally: Anorexia, dyspepsia, fever, nausea, rash, vomiting.
Topically: Dermatitis, paradoxical photosensitivity.
Serious Adverse Effects (Rare):
Orally: Hepatotoxicity.

Dermatologic ...Topically, PABA can cause contact dermatitis and sometimes paradoxical photosensitivity (272).

Gastrointestinal ...Orally, the most commonly reported side effects of PABA are diarrhea, nausea, vomiting, anorexia, dyspepsia, fever, and rash (1074). PABA should be discontinued if adverse effects prevent the patient from eating (10). In one report, up to 25% of patients discontinued PABA due to intolerance of side effects (1074).

Hematologic ...High dose PABA (up to 48 grams per day) can cause decreased white blood count below 4000 mm3 in approximately 30% of patients (1061).

Hepatic ...Liver toxicity, including fatal hepatitis has been reported in patients taking PABA in high doses (12-48 grams per day) (1061,1094). In one case, 12 grams per day for 2 months caused liver toxicity (1094). Increased liver function tests from PABA have also been noted (1084), and jaundice was reported in one case of treatment with PABA (68049). Despite these reports, a study reviewing the charts of 274 patients with scleroderma who were taking the potassium salt form of PABA as treatment found no evidence of hepatotoxicity (1065).

Immunologic ...Orally, PABA can cause allergic reactions including fever and skin rash (1074).

Neurologic/CNS ...Orally, PABA may cause headaches, which resolve upon discontinuation of treatment (1074).

Other ...Death has been reported in 3 children treated with 24 grams of PABA per day for rheumatic fever or arthritis. At autopsy, all had fatty changes in the liver, kidney, and myocardium (1061). Topical PABA and its derivatives have a tendency to discolor clothing due to a photo-oxidative reaction (68025).

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General ...Orally, tyrosine seems to be well tolerated. No serious adverse effects have been documented; however, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Fatigue, headache, heartburn, and nausea.

Gastrointestinal ...Orally, tyrosine can cause nausea and heartburn when taken at a dose of 150 mg/kg (7211). Taking tyrosine 4 grams daily in combination with 5-hydroxytryptophan 800 mg and carbidopa 100 mg can cause diarrhea, nausea, and vomiting. These effects can be mitigated by lowering the dosage (918).

Musculoskeletal ...Orally, larger doses of tyrosine (150 mg/kg) can cause arthralgia, but this is uncommon (7211).

Neurologic/CNS ...Orally, larger doses of tyrosine (150 mg/kg) can cause headache and fatigue (7211). Taking a combination of tyrosine 4 grams, 5-hydroxytryptophan 800 mg, and carbidopa 100 mg can cause drowsiness and agitation. These effects can be mitigated by lowering the dosage (918).

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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). Three cases of transient hypotension and tachycardia during intravenous administration of vitamin C have also been reported (114490).

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 (3042,4844,96707,104450,114493,114490). 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).

(Read more about VITAMIN C)

General ...There is currently a limited amount of information on the adverse effects of yucca. A thorough evaluation of safety outcomes has not been conducted.

Dermatologic ...Topically, yucca has been reported to cause phytodermatitis (68294). In one case report, an atopic gardener developed contact urticaria after occupational exposure to weeping fig, spathe flower, and yucca. Allergen skin tests were positive for all three plants (49961).

Gastrointestinal ...Orally, the saponins in yucca can be irritating to mucous membranes and might cause gastrointestinal irritation (7,4077).

Pulmonary/Respiratory ...Environmental exposure to yucca has been associated with allergic rhinitis in 59 patients who exhibited sensitization to yucca after allergen skin testing (86902).

(Read more about YUCCA)