Gold Standard Fit 40 by Optimum Nutrition

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Allergic rhinitis (hay fever). Although there has been interest in using oral black pepper for allergic rhinitis, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Asthma. Although there has been interest in using oral black pepper for asthma, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Athletic performance. Oral black pepper has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical trial in untrained males shows that taking a supplement containing black pepper extract 10 mg, caffeine 400 mg, capsicum extract 66.7 mg, and niacin 40 mg as a single dose prior to exercise does not improve strength, time to exhaustion, or maximal oxygen consumption when compared with placebo (37873).
• Depression. Although there has been interest in using oral black pepper for depression, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Diarrhea. Although there has been interest in using oral black pepper for diarrhea, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Dysmenorrhea. Although there has been interest in using oral black pepper for dysmenorrhea, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Dyspepsia. Although there has been interest in using oral black pepper for dyspepsia, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Fall prevention. It is unclear if inhaling black pepper oil as aromatherapy is beneficial for fall prevention in older adults. Details: One small clinical study in older adults shows that applying black pepper oil near the right side of the nose as an olfactory stimulant improves stability while the eyes are closed during a one-minute trial when compared with the application of water. The improvement with black pepper oil is comparable to the improvement seen with the application of lavender oil (29160). It is unclear if any benefit persists after inhalation of black pepper oil.
• Fatigue. It is unclear if oral black pepper is beneficial in patients with fatigue. Details: One small clinical trial in adults with below-average energy levels shows that taking black pepper 2 grams as a single dose does not improve sustained attention, motivation to perform cognitive tasks, or feelings of mental energy and mental fatigue when compared with placebo (91731).
• Flatulence. Although there has been interest in using oral black pepper for flatulence, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Headache. Although there has been interest in using oral black pepper for headache, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Insect bite. Topical black pepper 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 specific product (Trikatu) containing black pepper, long pepper, and ginger, as well as camphor, eucalyptus oil, and menthol, directly to mosquito bites does not reduce papule size, erythema, edema, or pruritis when compared with a control compound containing the same base ingredients but without the pepper and ginger components (89893).
• Obesity. Although there has been interest in using oral black pepper for obesity, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Pain (chronic). Although there has been interest in using topical black pepper for chronic pain related to various etiologies, including osteoarthritis, postherpetic neuralgia, and peripheral neuropathy, there is insufficient reliable information about the clinical effects of black pepper for these conditions.
• Rhinosinusitis. Although there has been interest in using oral black pepper for rhinosinusitis, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Sexual desire. Although there has been interest in using oral black pepper for increasing sexual desire, there is insufficient reliable information about the clinical effects of black pepper for this purpose.
• Smoking cessation. It is unclear if inhaling black pepper essential oil as aromatherapy is effective for smoking cessation. Details: One small clinical trial in adult male smokers who were deprived from smoking overnight shows that inhaling a vapor from the essential oil of black pepper, as needed over a 3-hour period, reduces cigarette cravings, negative feelings, and anxiety when compared with a placebo vapor (29159). Another small clinical study in patients addicted to dipping, chewing, or smoking tobacco shows that placing a drop of black pepper essential oil on tissue paper and inhaling for 2 minutes at least three times a day for 3 days reduces nicotine cravings when compared to baseline (90502).
• Swallowing dysfunction. It is unclear if inhaling black pepper oil as aromatherapy is beneficial in patients with swallowing dysfunction. Details: One small clinical study in post-stroke residents of nursing homes shows that one minute of olfactory stimulation with black pepper oil before each meal for 30 days decreases swallowing reflex latency by 11 seconds and increases the number of swallowing movements by 3.3 when compared to baseline (29161). A small clinical trial in children with neurological disorders who were on long-term enteral nutrition shows that applying black pepper oil to the nostrils or nasal cavity for one minute improves the amount of oral intake and swallowing movement in 63% of patients. Although oral intake increased, the need for enteral nutrition was not eliminated (29162).
• Vitiligo. It is unclear if topical piperine oil, a constituent of black pepper, is beneficial in patients with vitiligo. Details: A small clinical study in patients with vitiligo shows that applying piperine oil 1% daily in addition to receiving narrowband ultraviolet B (NB-UVB) light therapy every other day for 3 months improves repigmentation more rapidly when compared with using NB-UVB alone (103820). More evidence is needed to rate black pepper for these uses.

(Read more about BLACK PEPPER)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Burns. Although there has been interest in using topical cucumber fruit for burns, there is insufficient reliable information about the clinical effects of cucumber for this purpose.
• Diabetes. Although there has been interest in using oral cucumber seed for diabetes, there is insufficient reliable information about the clinical effects of cucumber for this purpose.
• Hyperlipidemia. It is unclear if oral cucumber seed is beneficial in patients with hyperlipidemia. Details: A small clinical trial in patients with mild hyperlipidemia shows that taking cucumber seed extract 500 mg orally daily for 6 weeks reduces levels of low-density lipoprotein (LDL) cholesterol by 27% and levels of triglycerides by 32%, compared with improvements of only 3% and 11%, respectively, in those taking placebo. High-density lipoprotein (HDL) cholesterol levels were also improved (103386).
• Hypertension. Although there has been interest in using oral cucumber stems for hypertension, there is insufficient reliable information about the clinical effects of cucumber for this purpose.
• Osteoarthritis. It is unclear if oral cucumber is beneficial in patients with osteoarthritis. Details: Two moderate-sized clinical trials in patients with moderate knee osteoarthritis shows that taking a specific cucumber extract (Q-Actin) 20 mg or 100 mg daily for 6 months improves the subjective measuresof pain, stiffness, and function at each time point beginning on day 30 when compared with placebo or glucosamine chondroitin. Improvements from baseline range from about 30% to 70% (103385,115615). The generalizability of these findings is limited by the fact that these studies included mostly patients from India or Cameroon (103385).
• Wound healing. Although there has been interest in using topical cucumber fruit for wound healing, there is insufficient reliable information about the clinical effects of cucumber for this purpose. More evidence is needed to rate cucumber for these uses.

(Read more about CUCUMBER)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral hops-derived bitter acids are beneficial for memory and attention in patients with age-related cognitive decline. Details: A small exploratory clinical study in older adults aged 45-64 years, with self-awareness of cognitive decline, shows that taking matured hops bitter acids (Kirin Holdings Co. Ltd) 35 mg daily for 12 weeks does not improve memory, attention, or performance on most cognitive tests when compared with placebo (102899). A follow-up clinical study in patients aged 45-69 years with subjective cognitive decline shows that taking the same dose of the same product for 12 weeks also does not improve memory, learning, or selective attention, but might improve divided attention as measured on the Symbol Digit Modalities Test (SDMT), when compared with placebo (105953). Both studies were funded by the supplement manufacturer and conducted in Japan; it is unclear if these findings are generalizable to other geographic locations.
• Anxiety. Although there is interest in using oral hops for anxiety, there is insufficient reliable information about the clinical effects of hops for this condition.
• Attention deficit-hyperactivity disorder (ADHD). Although there is interest in using oral hops for ADHD, there is insufficient reliable information about the clinical effects of hops for this condition.
• Body odor. Although there is interest in using topical hops to reduce body odor, there is insufficient reliable information about the clinical effects of hops for this purpose.
• Insomnia. Taking oral hops extract in combination with valerian root extract seems to be modestly beneficial in patients with insomnia. However, the effect of hops extract when used alone is unclear. Details: In patients with diagnosed sleep disorders, taking hops extract in combination with valerian root for at least 28 days seems to be beneficial. One clinical study in adults with mild insomnia shows that taking two tablets of a combination product containing a total of 83.8 mg hops extract and 374 mg valerian root extract nightly seems to modestly improve subjective sleep measures, including sleep latency, when compared with placebo, after 28 days. However, there was no difference in efficacy between treatment groups after only 14 days (15018). Additionally, a small clinical study in patients with non-organic sleep disorders shows that taking a specific fixed combination product (Ze91019) containing hops extract 120 mg and valerian root extract 500 mg daily for 28 days improves sleep latency when compared with placebo (19413). It is unclear if taking hops and valerian root as a single dose is beneficial in healthy patients. One small clinical study in healthy volunteers with poor sleep shows that taking a specific preparation (Dormeasan, Bioforce AG) containing hops extract 460 mg and valerian root extract 460 mg dissolved in 50 mL of honey water once at night increases total sleep time and time spent in deep sleep when compared with placebo (19418). However, another preliminary clinical study in healthy adults shows that taking a single dose of a specific product (Hova, Zyma S.A.) containing hops extract 200 mg and valerian root extract 400 mg does not improve sleep latency when compared with placebo (6248). Research also shows that taking certain combination products containing hops and at least two other ingredients can improve sleep quality. These combination products have combined hops with lemon balm and valerian (Valerina Natt) (19417); or passionflower and valerian (NSF-3, M/s Tablets India) (88193,89406). However, other combination products have not been beneficial. These have combined hops with soya oil, soya lecithin, and cannabis (Cyclamax, Persee Medica) (55382); or with vitamin B6, zizyphus extract, hydrolyzed milk protein (Lactium), and magnesium oxide (LZ Complex3, Sanofi) (95971).
• Dyspepsia. Although there is interest in using oral hops-derived bitter acids for dyspepsia, there is insufficient reliable information about the clinical effects of hops for this condition.
• Lactation. Although there is interest in using oral hops for increasing lactation, there is insufficient reliable information about the clinical effects of hops for this purpose.
• Menopausal symptoms. It is unclear if oral hops extract is beneficial in patients with menopausal symptoms. Details: Small clinical studies in patients with menopausal symptoms show that taking a specific hops extract (MenoHop, Biodynamics) 75.1-300 mg standardized to contain 100-200 mcg of 8-prenylnaringenin daily does not improve menopausal symptoms, including hot flashes, after 8-12 weeks of treatment when compared with placebo (55338,55370).
• Obesity. It is unclear if administering bitter hops extract intraduodenally or intragastrically is beneficial in patients with obesity. Details: A very small clinical study in healthy young adult males shows that intraduodenal or intragastric administration of bitter hops extract 100-250 mg once does not affect appetite perception, gastrointestinal symptoms, or subsequent energy intake when compared with control (112233). It is unclear if these results are generalizable to individuals with overweight or obesity.
• Overactive bladder. Oral hops extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An observational study in females with overactive bladder suggests that taking a specific combination product (Granu Fink femina, Omega Pharma) containing hops extract 18 mg, sweet sumac bark extract 56 mg, and pumpkin seed oil 227 mg three times daily for 12 weeks decreases the frequency of urination from an average of 0.9 to 0.4 episodes daily and the frequency of leakage when compared with baseline. The study also shows this specific combination product (Granu Fink femina, Omega Pharma) improves quality of life when compared with baseline (103253). The validity of these findings is limited by the lack of a control group. Also, it is unclear if these findings are due to hops extract, other ingredients, or the combination.
• Psychological well-being. It is unclear if drinking non-alcoholic beer containing matured hops bitter acids is beneficial in healthy adults. Details: A clinical study in healthy adults shows that consuming 350 mL of non-alcoholic beer containing matured hops bitter acids 35 mg (Kirin Holdings Co. Ltd) daily for 3 weeks improves mood scores on the Profile of Mood States 2 (POMS2) and Two-dimensional Mood Scale (TDMS) when compared with baseline (107813). The validity of these findings is limited by the lack of a control group.
• Sexual dysfunction. It is unclear if topical hops gel is beneficial in patients with postmenopausal vaginal atrophy. Details: A small clinical study in adults with postmenopausal vaginal atrophy shows that applying intravaginal topical gel containing hops extract (Barij Essence) daily for 7 days and then twice weekly thereafter for 2 months does not improve sexual desire, sexual arousal, vaginal lubrication, satisfaction, orgasm, sexual pain, or overall measures of sexual dysfunction when compared with intravaginal estradiol (112125). The validity of these effects is limited by baseline differences between groups.
• Shift work disorder. It is unclear if drinking non-alcoholic beer containing hops is beneficial in patients with shift work disorder. Details: A small open-label clinical study in healthy female nurses working rotating or night shifts shows that drinking 333 mL of non-alcoholic beer containing hops (San Miguel 0% alcohol) at dinner for 2 weeks reduces sleep latency by about 8 minutes, total activity during the night, andanxiety when compared with baseline. However, it does not appear to increase the duration of sleep (55403). The validity of these findings is limited by the lack of a control group and unconfirmed hops content in the beer.
• Vaginal atrophy. Topical hops extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An open-label, multicenter clinical study in postmenopausal patients with vaginal atrophy shows that inserting 2.5 grams of a vaginal gel containing hops extract 1%, hyaluronic acid, liposomes, and vitamin E (Gynomunal Vaginal gel or Esvegyne, Polichem SA) into the vagina daily for one week followed by twice weekly for 11 weeks reduces vaginal dryness, burning, itching, and rash when compared with baseline (55339). The validity of these findings is limited by the lack of a control group. Also, it is unclear if these effects are due to hops, other ingredients, or the combination.
• Venous leg ulcers. Although there is interest in using topical hops for venous leg ulcers, there is insufficient reliable information about the clinical effects of hops for this condition. More evidence is needed to rate hops for these uses.

(Read more about HOPS)

POSSIBLY EFFECTIVE

• Allergic rhinitis (hay fever). Oral turmeric seems to improve symptoms in people with allergic rhinitis. Details: A large clinical study in people with allergic rhinitis shows that taking a specific curcumin product (Organika Health Products) 500 mg daily for 2 months reduces nasal symptoms, including sneezing, itching, runny nose, and congestion, when compared with placebo (96138).
• Depression. Most research shows that oral curcumin, a constituent of turmeric, 1 gram daily improves symptoms of depression after 6 weeks when taken along with an antidepressant. However, it is unclear whether curcumin is beneficial when used for greater than 8 weeks. Details: Curcumin appears to be most beneficial for depression in middle aged patients compared to older patients, when taken for at least 6 weeks, and when used at a dose of at least 1 gram daily. In adults with major depressive disorder, a meta-analysis of data from six clinical studies, as well as individual studies not included in this analysis, show that taking curcumin 1 gram daily along with an antidepressant moderately improves depression symptoms when compared with placebo (96131,96139). Another meta-analysis of 10 studies shows symptom reductions in patients with major depression when combined with conventional antidepressants, but not when used alone in patients with milder depressive symptoms. However, the quality of the evidence is low (104971). When used alone, one clinical study shows that curcumin 1 gram daily for 6 weeks may be similarly effective to fluoxetine 20 mg daily. Taking both products together seems to be more effective than either product alone, increasing the response rate from 65% to 78% (89728). Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that curcumin extract at doses of 500-1000 mg daily is provisionally recommended for monotherapy or adjunctive use in mild to moderate depression (110318).
• Dyspepsia. Oral turmeric may be modestly beneficial for some patients with dyspepsia. In patients with functional dyspepsia, small clinical studies show that oral curcumin, a constituent of turmeric, is similarly effective when compared with the proton-pump inhibitor omeprazole. Details: Clinical research shows that taking turmeric 500 mg four times daily for 7 days can relieve overall symptoms of dyspepsia in 64% more patients than taking placebo (11144). A small, unblinded clinical study in patients with a type of dyspepsia called postprandial distress syndrome shows that taking turmeric 250 mg or 500 mg orally three times daily after meals for 4 weeks is associated with reductions in symptom scores which are similar to those seen with simethicone 60 mg three times daily for 4 weeks. However, the recurrence rate upon stopping therapy was about 14% with simethicone, compared with 43% to 46% with turmeric (104963). In patients with functional dyspepsia, taking the constituent curcumin appears similarly effective when compared with omeprazole, but might not provide further symptom reduction in those also taking famotidine or omeprazole (106063,106801,111599). One small clinical study in Iran shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg daily in addition to famotidine 40 mg daily for 30 days is no more effective for reducing overall symptoms of dyspepsia, such as abdominal pain, heartburn, bloating, and nausea, when compared with famotidine alone (106063). Another small clinical study in Thailand shows that taking curcumin 500 mg four times daily for 4 weeks is similarly effective for reducing dyspepsia severity and improving satisfaction when compared with an unspecified dose of omeprazole and more effective when compared with placebo (106801). Similarly, a moderate-size clinical study in Thailand shows that taking curcumin 500 mg four times daily for 4 weeks is similarly effective for reducing dyspepsia severity when compared with omeprazole 20 mg daily. However, taking curcumin and omeprazole in combination did not provide further symptom reduction (111599). The validity of these results is limited by the high rate of study dropouts.
• Hyperlipidemia. Research is conflicting on whether oral turmeric, curcumin, or curcuminoids can reduce serum lipids. Any improvement in lipids is likely to be small. Reasons for the conflicting findings may relate to turmeric formulation, duration of treatment, and/or the baseline cholesterol status of the included patients. Details: Results from meta-analyses of clinical research show inconsistent and conflicting results. One large meta-analysis of over 50 clinical studies in healthy adults and those with a variety of conditions shows that supplementation with turmeric or curcumin 80-4000 mg daily for 4-24 weeks reduces total cholesterol by 4 mg/dL, low-density lipoprotein (LDL) cholesterol by 5 mg/dL, and triglycerides by 7 mg/dL and increases high-density lipoprotein (HDL) cholesterol by 2 mg/dL when compared with placebo (112119). Two other meta-analyses of 27 clinical studies agree that taking turmeric, curcumin, or curcuminoids moderately reduce triglyceride levels but suggest that turmeric does not improve total cholesterol when compared with placebo. However, the meta-analyses contradict one another on whether turmeric and its constituents reduce LDL cholesterol or increase HDL cholesterol. (96128,96135). Additionally, a third meta-analysis of 10 clinical trials shows that taking up to 2400 mg daily of curcumin or curcuminoids, from turmeric or isolated sources, for up to 12 weeks, does not significantly improve triglycerides, LDL cholesterol, HDL cholesterol, or total cholesterol (110220).
• Nonalcoholic fatty liver disease (NAFLD). Oral curcumin, a constituent of turmeric, seems to attenuate fat deposition and improve some metabolic parameters in adults with NAFLD. Details: Clinical research shows that taking curcumin daily reduces NAFLD severity in 30% to 79% of patients, compared to 5% to 27.5% of patients receiving placebo. Curcumin also reduces the quantity of additional fat deposition in the liver to 0% to 4.5%, compared to 17.5% to 26% in those taking placebo. Most research shows that taking curcumin also reduces liver enzyme levels, body mass index (BMI), blood glucose levels, glycated hemoglobin (HbA1c), and total cholesterol when compared with placebo. Although some clinical research shows that taking curcumin improves levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides, a meta-analysis of clinical research shows that these lipid levels are not improved in patients with NAFLD, specifically (97430,97431,100258,102350,106062,107120,109279,111349). However, another meta-analysis of 14 small, heterogeneous clinical studies in adults with NAFLD, that included some of these studies, shows that taking various doses and forms of turmeric or curcumin modestly reduces liver enzyme levels, improves measures of insulin resistance, reduces waist circumference, and improves LDL, HDL, and triglyceride levels when compared with placebo (111348). A small clinical trial in patients with NAFLD given specific lifestyle recommendations shows that taking curcumin modestly reduces the frequency of metabolic syndrome and fatty liver but does not have beneficial effects on fatty liver-associated indices, adiposity, or the atherogenic index, when compared with placebo (109285). Findings for specific endpoints are mixed between individual studies and may depend on the formulation of curcumin used or the duration of treatment. These studies have used various doses and formulations. In one study, 500 mg of a dispersion formulation equivalent to 70 mg of curcumin daily for 8 weeks was used (97430). Also, 250 mg once daily or 500 mg twice daily of a specific phytosomal formulation (Meriva, Indena) containing curcumin and soy phosphatidylcholine in a 1:2 ratio and standardized to an overall curcuminoid content of 20% was taken for 8 weeks (97431,106062). Another study used 1 gram of powdered turmeric rhizome taken three times daily with meals for 12 weeks (102350). One study used a curcumin-piperine complex (Curcumin C3 complex 500 mg plus Bioperine 5 mg) daily for 8 weeks (107120). One study used curcumin (Arjuna Natural Extract) 500 mg three times daily for 12 weeks (109285). Despite positive results with curcumin in several small clinical studies of patients with NAFLD, there is some concern that curcumin might cause hepatotoxicity in rare cases, especially when highly bioavailable formulations are used in high doses (103633). There is also evidence that the risk for hepatotoxicity with curcumin may be increased in individuals with the HLAB*35:01 allele (109288). Curcumin-induced hepatotoxicity has not been reported in clinical trials of patients with NAFLD, and its potential mechanism is unclear. However, patients seeking to take curcumin for NAFLD should be advised to monitor for symptoms of hepatotoxicity, including abdominal pain, dark urine, fatigue, jaundice, nausea, and pruritus.
• Oral mucositis. Oral curcumin or curcumin-containing mouthwash seem to reduce the development of severe oral mucositis, as well as reduce the severity and pain of oral mucositis, associated with cancer treatment. Details: Clinical research in patients receiving radiotherapy following recent radical surgery for oral cancer shows that taking turmeric (BCM-95, Arjuna Natural Pvt. Ltd., India) during radiotherapy reduces the incidence of severe oral mucositis to 25% or 20% in those taking turmeric 500 mg two or three times daily, respectively, compared with 65% in those taking placebo. The incidences of severe oral pain, dysphagia, and dermatitis were also reduced by at least 50% (105398). A small clinical study in patients receiving chemotherapy with or without head and neck radiotherapy shows that taking a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina) 80 mg twice daily for 7 weeks improves severity of oral mucositis at weeks 1, 4, and 7 and reduces pain at week 7 when compared with placebo. Effects were more pronounced in those with chemotherapy-induced oral mucositis than radiotherapy-induced oral mucositis (106800). In patients with head and neck cancer receiving radiotherapy, preliminary clinical research shows that swishing with 10 mL of turmeric solution (prepared by dissolving turmeric 400 mg in 80 mL of water) six times daily for 6 weeks delays mucositis and reduces the number of cases of intolerable mucositis by 49% when compared to swishing with 10 mL of povidone-iodine solution twice daily for 6 weeks (89726). Another small clinical study shows that swishing with 10 mL of nanoparticulate curcumin 0.1% mouthwash three times daily for 6 weeks is associated with a 50% lower risk of developing oral mucositis, and a delay of 2 weeks in the onset of mucositis, when compared with benzydamine 0.15% mouthwash (104969). A small clinical study in patients with mucositis due to head and neck radiotherapy shows that taking curcumin nanoparticles (SinaCurcumin, ExirNanoSina) 40 mg daily or using 10 mL of a curcumin 0.1% mouthwash three times daily for up to 21 days improves scores related to pain, burning, ulceration, and erythema when compared with placebo. Results with either oral or topical curcumin were similar (111350).
• Osteoarthritis. Some oral turmeric extracts and combination products containing turmeric seem to improve certain symptoms of knee osteoarthritis. However, it is unclear how turmeric compares to the use of non-steroidal anti-inflammatory drugs (NSAIDs). Details: Several meta-analyses of clinical studies show that turmeric extracts and/or curcuminoid products reduce knee pain and stiffness, improve physical function, and reduce the need for rescue medication when compared with placebo (104970,106792,109280,110222). However, a reduced effect was noted in patients with increasing age or body mass index (104790). The studies evaluated in these meta-analyses are heterogeneous, of low- to moderate-quality, and utilized a variety of products and/or dosing strategies (104970,106792,109280,110222). Small to moderate-sized clinical studies show that specific products (Meriva, Indena; Theracurmin, Theravalues Corp) containing curcumin 90-100 mg twice daily for up to 6 months, or specific turmeric extracts (Turmacin, Natural Remedies Pvt. Ltd.; Curcugen, DolCas Biotech, LLC) 500 mg twice daily for 6-12 weeks, reduce pain and analgesic use and improve functionality when compared with placebo (17953,80988,89721,97424,104148,107118). A specific turmeric extract (CuraMed, EuroPharma USA) 1500 mg daily for 12 weeks improves functionality, but not pain, when compared with placebo (96127). Also, a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina), 40 mg twice daily for 6 weeks, improves pain, stiffness, and physical activity scores and reduces intake of rescue acetaminophen by about 60% when compared with placebo (102349). However, not all turmeric products seem to be effective for improving symptoms of osteoarthritis. One small clinical study shows that taking a specific turmeric extract (B-Turmactive, PLAMECA S.A.) 500 mg daily for one week does not reduce knee pain when compared with placebo (104147). Also, a meta-analysis of clinical research shows that benefits are limited to bio-optimized forms of curcuminoids, and benefits related to pure extracts are lacking (110222). Turmeric has also been compared with conventional treatments for knee osteoarthritis in small meta-analyses, a network meta-analysis, and individual clinical studies. However, the evidence is mixed as to whether turmeric is as effective or more effective than NSAIDs, such as ibuprofen 400 mg taken 2-3 times daily, diclofenac 25-100 mg daily, or chondroprotective drugs (17952,89720,89722,106792,109280,110222,113607). A network meta-analysis comparing 6 interventions in adults with knee osteoarthritis suggests that curcumin monotherapy, curcumin with chondroprotective agents, or curcumin with NSAIDs improves scores related to pain, function, and stiffness while reducing the need for rescue medication and the incidence of adverse events (113607). Individual studies are heterogenous with respect to comparator medication and dosing schedule. Doses included a non-commercial turmeric extract 500 mg 3-4 times daily for 4-6 weeks (17952,89720) or turmeric extract 500 mg twice daily for 3 months (89722). Topical turmeric has also been evaluated. One clinical study shows that applying curcumin topically as a 5% ointment in Vaseline twice daily for 6 weeks reduces pain associated with knee osteoarthritis by a mean of about 11 on a 100-point visual analog scale when compared with placebo (104964). Another clinical study in patients with knee osteoarthritis shows that applying curcumin in a self-nano-emulsifying polyethylene glycol organogel 1.5 grams to the knee twice daily for 8 weeks reduces pain, stiffness, and difficulty with physical function scores by 72%, 62%, and 46%, respectively, when compared to baseline, with improvements superior to placebo for all outcomes (113357). Research also shows that taking specific combination products containing turmeric and other ingredients can improve pain and functionality in patients with osteoarthritis. These combination products have combined turmeric with chondroitin sulfate and glucosamine hydrochloride (CartiJoint Forte, Fidia Farmaceutici SpA); boswellic acid (Curamin, EuroPharma USA; Rhulief); Boswellia serrata (Rhulief); ashwagandha, Boswellia serrata, and zinc (Articulin-F, Eisen Pharmaceutical Co. Pvt. Ltd.); devil's claw and bromelain (AINAT, Laboratoire de Rhumatologie Appliquée); Boswellia serrata, guggul, and valerian (Phytoproflex, OPTM Healthcare); Boswellia serrata and terminalia (LI73014F2, Laila Nutraceuticals); ashwagandha, Boswellia serrata, and ginger (Artrex, Mendar); or extracts of ginger rhizome, devil's claw tuber, Boswellia serrata resin, and celery seed (Tregocel, Max Biocare) (19276,51950,81466,89717,89719,96127,97419,97421,97428,106078)(109280).
• Pruritus. Oral turmeric has been evaluated for the management of pruritus of various etiologies, with promising results. Details: Clinical research in patients with kidney failure shows that taking turmeric 500 mg orally three times daily for 8 weeks decreases symptoms of uremic pruritus by 1.9-fold when compared with placebo (89724). Also, a small clinical study in patients with sulfur mustard-induced chronic pruritus shows that taking a specific combination product (C3 Complex, Sami Labs LTD) containing curcumin 1 gram plus extract from black pepper or long pepper (Bioperine) daily for 4 weeks reduces pruritus severity and improves quality of life when compared with placebo (81120,81176).

POSSIBLY INEFFECTIVE

• Alzheimer disease. Neither oral turmeric nor its constituent curcumin appears to improve cognitive function or attenuate cognitive decline in adults with this condition. Details: A small clinical trial shows that taking the turmeric constituent, curcumin, 1-4 grams daily for 6 months does not improve mental state examination scores when compared with placebo (17096). Furthermore, a meta-analysis of this study and another small clinical study in patients with Alzheimer disease shows that the turmeric group experienced greater cognitive decline when compared with placebo (100261). While this research is limited by small study sizes and heterogeneous patient populations, the current evidence does not support the use of turmeric in patients with this condition.
• Peptic ulcers. Oral turmeric does not seem to improve the healing of peptic or gastric ulcers when compared with placebo or liquid antacids. Details: Some clinical research shows that taking turmeric 2 grams three times daily for 8 weeks does not improve the healing of peptic ulcers when compared with placebo in Vietnamese patients (81444). Also, taking powdered turmeric rhizome 250 mg four times daily for 6 weeks seems to be less effective than a liquid aluminum-magnesium-hydroxide antacid for promoting gastric ulcer healing (81284).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Although there has been interest in using topical turmeric for acne, there is insufficient reliable information about the clinical effects of turmeric for this purpose.
• Age-related cognitive decline. Some small clinical studies suggest that oral curcumin, a constituent of turmeric, may modestly improve cognition in elderly patients experiencing cognitive decline. Details: A meta-analysis of three small clinical trials shows that curcumin modestly improves cognition in the elderly (100261). One of these clinical trials shows that taking a specific brand of curcumin (Theracurmin, Theravalues Corp.) 90 mg twice daily for 18 months improves long-term memory and attention when compared with placebo in middle-aged and older adults with or without mild cognitive impairment (96161).
• Amenorrhea. Although there has been interest in using oral turmeric for amenorrhea, there is insufficient reliable information about the clinical effects of turmeric for this purpose.
• Ankylosing spondylitis. Although there has been interest in using oral turmeric for ankylosing spondylitis, there is insufficient reliable information about the clinical effects of turmeric for this purpose.
• Aromatase inhibitor-induced arthralgia. It is unclear if oral curcumin, a constituent of turmeric, is beneficial for aromatase inhibitor-induced arthralgia. Details: A small clinical trial in patients experiencing aromatase inhibitor-induced arthralgia shows that taking curcuminoids as a nanoemulsion (Curcumin C3 Complex, Sabinsa Corporation) 200 mg daily for 3 months does not improve grip strength or joint symptoms when compared with placebo (113345). However, this study may have been underpowered to detect a difference between groups.
• Asthma. Some small clinical studies suggest that oral turmeric, as an adjunct to conventional asthma treatment, does not improve lung function or symptoms in adults and children with asthma. Details: One small clinical study in adults with mild to moderate asthma shows that adjuvant therapy with turmeric as curcumin 500 mg twice daily for 30 days does not improve lung function based on FEV1, or improve symptoms such as dyspnea, wheezing, cough, or tightness, when compared to standard treatment alone (99349). A small clinical trial in children 7-18 years of age with moderate to severe asthma shows that adding turmeric 500-1000 mg (containing 20-40 mg curcuminoids) daily for 6 months to standard therapy does not improve overall asthma symptoms when compared with placebo and standard therapy, although it may decrease the frequency of nighttime awakenings and the use of rescue inhalers (99348). Due to their small sizes and high drop-out rates, these studies may have been underpowered to detect a difference between groups.
• Athletic performance. It is unclear if oral curcumin, a constituent of turmeric, is beneficial for athletic performance. Details: Preliminary clinical research in middle-aged male long-distance runners shows that taking a turmeric extract providing 2 grams of curcumin 95% and piperine 5% daily for 6 weeks does not improve aerobic capacity when compared with placebo (109286).
• Benign prostatic hyperplasia (BPH). It is unclear if oral curcumin, a constituent of turmeric, is beneficial in BPH. Details: A clinical study in patients with BPH shows that taking curcumin 2250 mg once daily along with tamsulosin and finasteride for 6 months improves lower urinary tract symptoms related to storage, but not overall symptoms or symptoms related to voiding, by about 35%, compared with 25% in those receiving tamsulosin and finasteride alone. Periprostatic fat thickness, quality of life, and erectile function also were improved (106799).
• Beta-thalassemia. It is unclear if oral turmeric is beneficial for iron overload in patients with beta-thalassemia. Details: A small clinical study in patients with beta-thalassemia major and iron overload shows that taking turmeric extract containing curcumin 500 mg twice daily for 12 weeks modestly reduces non-transferrin bound iron (NTBI) by 0.6 micromol/L, but not hemoglobin, transferrin saturation, total iron binding capacity, ferritin, or hepcidin, when compared with placebo (99306). Another small clinical study in adult males with beta-thalassemia intermedia and iron overload shows that taking a higher dose of curcumin 500 mg three times daily for 12 weeks modestly reduces serum iron and ferritin turmeric levels and transferrin saturation when compared with placebo (108871).
• Bruises. Although there has been interest in using topical turmeric to alleviate bruising, there is insufficient reliable information about the clinical effects of turmeric for this purpose.
• Cachexia. It is unclear if oral curcumin, a constituent of turmeric, is beneficial for cancer cachexia. Details: A small clinical trial in patients with cancer anorexia-cachexia syndrome shows that taking curcumin 800 mg twice daily for 8 weeks does not reduce weight loss or improve body composition or handgrip strength when compared with placebo (109283).
• Canker sores. Some preliminary research suggests that topical curcumin, a constituent of turmeric, is beneficial for minor canker sores. Details: Preliminary clinical research in young adults with minor canker sores shows that applying a 2% curcumin oral gel for 6 months reduces ulcer size, pain, and recurrence rate and increases healing rate similarly to 0.1% triamcinolone oral paste (104962). The validity of the study is limited by a lack of investigator blinding and the lack of an intention to treat analysis. Another small clinical study shows that applying a 1% curcumin nanomicelle gel (SinaCurcumin Pharmaceuticals) on lesions three times daily for one week is modestly more effective than applying a 2% curcumin gel for reducing pain and ulcer size (109282). The validity of this finding is limited by the lack of a non-curcumin comparator group.
• Carpal tunnel syndrome. Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is unclear if topical curcumin, a constituent of turmeric, is beneficial for carpal tunnel syndrome. Details: A moderate-sized clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing turmeric, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, and vitamins C, E, B1, B2, B6, and B12 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 turmeric, other ingredients, or the combination. Topical turmeric has also been investigated. A small clinical study in patients with mild to moderate carpal tunnel syndrome shows that applying a 1% curcuminoid gel (Sinanomin) to the wrists twice daily for 8 weeks modestly decreases symptom severity and improves function when compared with a placebo gel. However, there was no change in electrodiagnostic testing of the injury. All patients also used a night splint (113356).
• Chemotherapy-induced acral erythema. It is unclear if oral or topical turmeric reduces the risk for acral erythema from capecitabine. Details: A small clinical trial in adults with cancer shows that taking turmeric 4 grams daily for 6 weeks starting at the beginning of treatment with capecitabine does not reduce the incidence of acral erythema overall; however, it does seem to reduce acral erythema grade 2 or higher when compared with expected incidence rates (99309). Topical turmeric has also been evaluated. A clinical study in patients with colorectal, gastric, pancreatic, or breast cancer receiving capecitabine shows that applying a specific ointment (Alpha) standardized to contain curcumin extract 0.5% and henna extract 10% to the soles and palms twice daily, beginning on day 1 of chemotherapy and continued for 4 cycles, does not prevent acral erythema or improve World Health Organization severity scores when compared with placebo. A post-hoc analysis suggests that there may have been a trend toward delayed onset and progression; however, this study was not structured to assess these outcomes (108874).
• Chemotherapy-induced constipation. It is unclear if oral curcumin reduces symptoms of chemotherapy-induced constipation. Details: A small clinical study in patients with various forms of cancer receiving standard chemotherapy for that cancer type shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg twice daily for 9 weeks does not reduce symptoms of constipation when compared with placebo (107111).
• Chemotherapy-induced diarrhea. It is unclear if oral curcumin reduces symptoms of chemotherapy-induced diarrhea. Details: A small clinical study in patients with various forms of cancer receiving standard chemotherapy for that cancer type shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg twice daily for 9 weeks does not reduce symptoms of diarrhea when compared with placebo (107111).
• Chemotherapy-induced nausea and vomiting (CINV). It is unclear if oral curcumin reduces CINV. Details: A small clinical study in patients with various forms of cancer receiving standard chemotherapy for that cancer type shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg twice daily for 9 weeks modestly reduces symptoms of nausea, but not vomiting, in the second and third months after the start of treatment when compared with placebo (107111).
• Chemotherapy-induced peripheral neuropathy. It is unclear if oral curcumin reduces symptoms of chemotherapy-induced peripheral neuropathy. Details: A small clinical study in patients with various forms of cancer receiving standard chemotherapy for that cancer type shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg twice daily for 9 weeks modestly reduces symptoms of chemotherapy-induced peripheral neuropathy over a three-month period when compared with placebo (107111).
• Chronic kidney disease (CKD). It is unclear if oral turmeric is beneficial for CKD. Details: A meta-analysis of four small clinical trials in patients with CKD related to diabetic nephropathy or lupus nephritis shows that taking curcumin or turmeric for 0.5-4 months moderately reduces proteinuria when compared with placebo (109276). Also, a small clinical trial in children and young adults ages 6-25 years with vascular dysfunction related to autosomal dominant polycystic disease (PKD) shows that curcumin powder 25 mg/kg daily for 12 months does not improve vascular function or kidney function when compared with placebo (107117).
• Colorectal adenoma. It is unclear if oral turmeric is beneficial for managing colorectal adenoma. Details: Preliminary clinical research in adults with familial adenomatous polyposis shows that taking curcumin 1500 mg twice daily for 12 months does not reduce the quantity or size of lower intestinal adenomatous polyps when compared with placebo (97427). A very small clinical trial in patients with familial adenomatous polyposis shows that taking 8 capsules daily of a turmeric extract, in a formulation also containing pepper fruit, spirulina, seaweed, and ginger root, for 6 months does not affect total polyp number or burden when compared with placebo. However, both number and burden were modestly reduced in the left colon. Each capsule provided curcuminoids 123.65 mg and turmerones 26.79 mg (110223).
• Colorectal cancer. It is unclear if oral turmeric is beneficial for the prevention or treatment of colorectal cancer. Details: A small clinical trial in patients undergoing chemotherapy following colorectal cancer surgery shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg daily for 8 weeks modestly improves some measures of quality of life when compared with placebo (107109). In addition, a small clinical study in people at high risk for colorectal cancer, such as those who smoke, shows that taking the turmeric constituent, curcumin, 4 grams daily for 30 days can reduce the number of precancerous rectal aberrant crypt foci (18204). It is not clear if this results in a reduced risk for colorectal cancer.
• Coronary artery bypass graft (CABG) surgery. One small study suggests that oral turmeric may reduce the risk for myocardial infarction after CABG surgery. Details: Preliminary clinical research shows that taking the turmeric constituent, curcuminoids, 4 grams daily in four divided doses, beginning 3 days prior to surgery and continuing for 5 days post-surgery, decreases the relative risk of myocardial infarction following CABG by approximately 56% when compared with placebo (81143).
• Coronavirus disease 2019 (COVID-19). It is unclear if oral turmeric or its constituent, curcumin, is beneficial for reducing symptoms of COVID-19. Details: Small studies have evaluated curcumin as an adjunctive therapy in adults hospitalized with confirmed COVID-19. Patients in these studies also received treatments such as antimicrobials, anti-inflammatory medications, anticoagulants, antiretrovirals, and immunosuppressants (104966,105393,107119). One study shows that adding curcumin reduces the duration of shortness of breath by 6-9 days when compared with patients who received other treatments in combination with probiotics. However, there were no differences in the duration of other symptoms, including fever, cough, or sore throat. Subgroup analyses suggest that taking curcumin may improve oxygenation and reduce the need for supplemental oxygen or ventilation (105393). Another study shows that adding curcumin modestly reduces the time to resolution of COVID-19 symptoms, the length of supplemental oxygen use, and the likelihood for deterioration in the patients' condition when compared with patients who received other treatments alone (104966). A third study shows some benefit of curcumin on fever and cough when compared with baseline; however, it is unclear if any changes were significant when compared with placebo (107119). Doses of curcumin used in these studies include curcumin 525 mg with piperine 2.5 mg (C3 Complex, SamiDirect) twice daily, starting at admission and continuing for 14 days (105393), or a specific nanocurcumin product (SinaCurcumin, ExirNanoSina) 80 mg twice daily for 2 weeks or 240 mg daily in divided doses for 7 days (104966,107119). Limitations of these studies include the small number of patients with severe symptoms, the large number of outcomes evaluated, the inconsistencies in other treatments used, the lack of clarity related to presentation of some results, and, in most cases, a lack of blinding. Turmeric has also been evaluated in adults in the outpatient setting with suspected or confirmed mild to moderate COVID-19. One small clinical study shows that taking curcumin (SinaCurcumin, ExirNanoSina) 80 mg twice daily for 14 days in addition to other COVID-19 treatments (mainly hydroxychloroquine and azithromycin) reduces the duration of cough, chills, myalgia, and smell and taste disturbance, but not dyspnea, fever, sore throat, or others, by 1-2 days when compared with placebo with other treatments (106802). The validity of this study is limited by the lack of confirmatory diagnosis at baseline and lack of consistency with other treatments, as well as the unclear reporting of symptom duration in relation to the initiation of treatment. Another small clinical study in outpatients confirmed to have COVID-19 shows that taking curcumin 1000 mg plus piperine 10 mg (Sami Labs Limited) daily for 14 days modestly improves weakness, but not cough, pain, headache, difficulty breathing, or biochemical indices, when compared with placebo (109278). Some research has also examined the effect of turmeric as part of a polyherbal combination. Clinical research in patients hospitalized for moderate COVID-19 symptoms shows that using an Ayurvedic formulation 1776 mg twice daily containing turmeric, ashwagandha, ginger, and Boswellia serrata (BV-4051) for 14 days modestly reduces the duration of illness and reduces the severity of fever, cough, and smell and taste dysfunction when compared to placebo. There was no beneficial effect on other symptoms, including nasal congestion, breathing difficulty, headache, and gastrointestinal symptoms. More than half of the patients were also treated with remdesivir which did not impact the majority of these findings (109899).
• Crohn disease. It is unclear if oral turmeric is beneficial for improving symptoms of active Crohn disease. Details: Some clinical research shows that taking the turmeric constituent, curcumin, 1.08 grams daily for one month, then 1.44 grams daily for one month, can reduce bowel movements, diarrhea, and abdominal pain when compared to baseline in patients with Crohn disease (79730). The validity of these findings is limited by the lack of a comparator group.
• Denture stomatitis. Topical turmeric may be beneficial for treating denture stomatitis. Details: A small clinical study in patients with denture stomatitis shows that applying topical curcumin gel (Curenext, Abbott Laboratories) three times daily for 2 weeks resolves denture stomatitis lesions similarly to clotrimazole ointment (106797).
• Diabetes. Low-quality clinical studies suggest that oral curcumin, a constituent of turmeric, may modestly improve glycemic control in patients with diabetes. Details: A meta-analysis of small clinical trials in patients with diabetic kidney disease shows that curcumin reduces levels of fasting glucose by approximately 8.3 mg/dL when compared with placebo. Curcumin was used in doses of 66.3-1670 mg daily for 2-6 months (107114). Preliminary clinical research included in the analysis shows that taking a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina) 80 mg daily for 12 weeks reduces fasting blood glucose by about 20 mg/dL (104149). Other meta-analyses of low- to moderate-quality clinical studies in patients with a variety of conditions including type 2 diabetes show that taking turmeric extract, curcumin, or curcuminoids for 4-36 weeks improves glycated hemoglobin (HbA1c) by 0.4-0.7% and reduces fasting glucose by approximately 13 mg/dL when compared with placebo or conventional treatment (106806,108877,113604). The validity of these findings is limited by the heterogeneity of the included studies and broad curcuminoid doses ranging from 46-1500 mg daily. Conversely, other meta-analyses in patients with type 2 diabetes show that curcumin does not reduce HbA1c or insulin levels when compared with placebo (104965,108877,113604).
• Diabetic foot ulcers. It is unclear if oral curcumin is beneficial in patients with diabetic foot ulcers. Details: Preliminary clinical research in patients with grade 3 diabetic foot ulcers shows that taking nanocurcumin 80 mg orally daily for 12 weeks does not improve glycated hemoglobin (HbA1c) or change the rate of ulcer healing when compared with placebo. Taking turmeric did result in modest decreases in fasting blood glucose, insulin levels, and insulin resistance (104972).
• Diabetic nephropathy. It is unclear if oral curcumin is beneficial in patients with diabetic nephropathy. Details: Meta-analyses of two to four small clinical trials in patients with diabetic kidney disease show that curcumin modestly improves serum levels of creatinine, total cholesterol, and fasting glucose, and reduces systolic blood pressure by 4 mmHg, when compared with placebo. However, there was no effect on diastolic blood pressure, proteinuria, or serum levels of other plasma lipids or blood urea nitrogen. Curcumin was used in doses of 66.3-1670 mg daily for 2-6 months (107114). One small study included in this analysis, which evaluated patients receiving hemodialysis, shows that taking a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina) 80 mg daily for 12 weeks reduces fasting blood glucose by about 20 mg/dL when compared with placebo (104149).
• Dysmenorrhea. Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in university students aged 18 to 24 in Iran with mild to severe primary dysmenorrhea and premenstrual syndrome (PMS) shows that taking a specific combination product containing curcumin 500 mg plus extract from black pepper 5 mg (C3 Complex, Sami Labs) daily, starting 7 days prior to menstruation and continuing for 3 days after menstruation for 3 consecutive menstrual cycles, does not improve the severity of symptoms when compared with placebo (106805). Conversely, a small clinical study in adults with moderately painful dysmenorrhea shows that taking a single dose of a combination product containing turmeric, Boswellia serrata, and sesame (Rhuleave-K, Arjuna Natural Private Ltd.) 1000 mg at the start of menstruation relieves menstrual cramp pain and reduces pain intensity for up to 6 hours when compared with placebo (112806). However, it is unclear if these effects are due to turmeric, other ingredients, or the combinations.
• Endometriosis. It is unclear if oral turmeric is beneficial for reducing pain due to endometriosis. Details: A small clinical study in adults with endometriosis shows that taking the turmeric constituent, curcumin, 500 mg twice daily for 8 weeks does not affect pain associated with endometriosis or quality of life when compared with placebo (113603).
• Erythema. Although there has been interest in using topical turmeric for reducing erythema, there is insufficient reliable information about the clinical effects of turmeric for this purpose.
• Exercise-induced muscle soreness. It is unclear if oral turmeric is beneficial for reducing muscle soreness from exercise. Details: A small clinical study in healthy males shows that taking turmeric capsules containing curcumin 2.5 grams twice daily for 5 days, starting 2.5 days before exercise, slightly reduces pain from certain movements when compared with placebo (98998). Another small crossover clinical study in professional male soccer players shows that taking curcumin 500 mg (Elite Opti-Turmeric, Health Span) immediately, 12 hours, and 36 hours after a match accelerates muscle recovery and reduces delayed-onset muscle soreness when compared with medium chain triglyceride oil 1000 mg (111356). Turmeric has also been examined in combination with other ingredients. Clinical research in healthy active adults with moderate to severe exercise-induced muscle pain shows that taking a single, 1000-mg dose of turmeric and Boswellia serrata extracts in black sesame oil (Rhuleave-K; Arjuna Natural Private Ltd.) improves pain relief when compared with placebo, with maximal benefits within about 3 hours. The number of people needed to treat to obtain pain relief of at least 50% over a 6-hour period was 1.1 (109277).
• Gingivitis. Small clinical studies suggest that oral turmeric and turmeric mouthwash may reduce the severity of gingivitis. Turmeric mouthwash appears to be similarly effective to chlorhexidine mouthwash. Details: A meta-analysis of generally preliminary clinical research shows that rinsing with a mouthwash containing curcumin for 3-4 weeks is as effective as rinsing with chlorhexidine for reducing the severity of gingivitis or plaque (106059). Mouthwashes in these studies contained 0.05% to 20% curcumin and were usually used twice daily for 3-4 weeks (81127,89723,106059). One mouthwash contained 0.05% turmeric extract and 0.005% eugenol (89723). Another small clinical trial shows that taking a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina) 80 mg daily by mouth after breakfast for 4 weeks reduces the severity of gingivitis and gingival bleeding, but not plaque, when compared with placebo in patients with gingivitis and mild periodontitis (104146).
• Gout. Although there is interest in using oral turmeric for gout, there is insufficient reliable information about the clinical effects of turmeric for this condition.
• Gulf war syndrome. It is unclear if oral curcumin is beneficial in patients with Gulf war syndrome. Details: A small preliminary clinical trial in patients with Gulf war syndrome shows that taking curcumin (Meriva, Indena, S.p.A.) 500 mg twice daily for 30 days reduces overall symptoms, including pain, fatigue, gastrointestinal distress, and others, by 19% when compared with baseline. Taking a higher dose of 2000 mg twice daily for an additional 30 days appears to be no more effective than the lower dose (105395).
• Helicobacter pylori. Small clinical studies suggest that oral turmeric is not beneficial for eradicating H. pylori when used alone or in combination with standard triple therapy or famotidine. Details: One small clinical study in patients with H. pylori gastritis shows that taking turmeric 2.1 grams daily for 4 weeks is less effective for eradicating H. pylori than taking an omeprazole-based triple regimen for one week (80957). Another small study in adults with peptic ulcers shows that taking a specific curcumin product (C3 Complex, Sami Labs LTD) 500 mg daily for 7 days, in conjunction with standard triple therapy, does not improve H. pylori eradication rates when compared with standard triple therapy alone. The addition of curcumin increased the resolution of dyspepsia symptoms by an additional 21%, but the clinical significance of this outcome is unclear (97420). In patients with dyspepsia, most of whom tested positive for fecal H. pylori antigen, clinical research shows that taking curcuminoids (C3 Complex, Sami Labs) 500 mg with piperine (Bioperine) 5 mg daily in addition to famotidine 40 mg daily for 30 days is no more effective for reducing fecal H. pylori antigen levels than taking famotidine alone (106063).
• Hypertension. It is unclear if oral curcumin is beneficial in patients with hypertension. Details: A meta-analysis of approximately 30 clinical studies in healthy adults or patients with a variety of conditions shows that taking turmeric, curcumin, curcuminoids, or nano-curcumin for 4 to 24 weeks reduces systolic blood pressure by about 2 mmHg and diastolic blood pressure by about 0.8 mmHg when compared with placebo (113602). However, these blood pressure reductions may not be clinically meaningful. In addition, most of the included studies were small and utilized heterogeneous dosing regimens.
• Impaired glucose tolerance (prediabetes). Oral turmeric may modestly improve glucose control in some patients with prediabetes. Details: In overweight or obese individuals with prediabetes, clinical research shows that taking a turmeric extract (BCM95 or Cucugreen; M/s Arjuna Natural Pvt Ltd.) 500 mg daily, providing 95% curcuminoids and at least 65% curcumin, for 90 days, either alone or in combination with zinc 30 mg as zinc gluconate, results in a small reduction in fasting glucose and glycated hemoglobin (HbA1c) when compared with placebo. There was also a small benefit in insulin sensitivity (105391). Other preliminary clinical research in adults with prediabetes shows that taking 500 mg of a combination of turmeric extract and Indian gooseberry extract in a 1:2 ratio along with phosphatidylcholine (EmbliQur) twice daily for 6 months modestly reduces fasting glucose and improves insulin resistance, when compared with placebo. However, changes in most other endpoints were not significantly different from placebo. Each 500 mg capsule contained turmeric extracts 29.86% and turmeric oil 1.27% (113355). The effect of turmeric on progression to type 2 diabetes in patients with prediabetes has also been investigated. Preliminary clinical research shows that taking a turmeric extract containing curcumin 750 mg twice daily for 9 months reduces the percentage of patients with prediabetes who develop type 2 diabetes when compared with placebo (81163).
• Irritable bowel syndrome (IBS). It is unclear if oral turmeric is beneficial for improving symptoms of IBS. Details: Preliminary clinical research in otherwise healthy adults with IBS shows that taking a turmeric extract (Cynara Turmeric, Lichtwer Pharma) 72-144 mg daily for 8 weeks reduces IBS symptoms by about 40% to 60% when compared to baseline (79565). The validity of this finding is limited by the lack of a comparator group. Taking a combination product (CU-FEO, Alfa Wasserman S.p.A.) containing curcumin 42 mg and fennel essential oil 25 mg per capsule twice daily for 60 days improves overall ratings of abdominal pain, abdominal distention, and quality of life by 24% when compared with placebo (97422). It is unclear if these effects are due to turmeric, fennel, or the combination. Observational research suggests that adding a supplement (Enterofytol PLUS) providing curcumin 42 mg and berberine 200 mg twice daily for 2 months to conventional IBS treatment is associated with improvements in symptoms, such as abdominal discomfort, distension, and stool status, by up to 48% when compared with conventional treatment alone. Use of the supplement was also associated with a 64% reduced need for conventional treatments (113354).
• Joint pain. Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking capsules of a specific combination product (Instaflex Joint Support, Direct Digital) containing glucosamine sulfate 1500 mg, methylsulfonylmethane 500 mg, white willow bark extract 250 mg, ginger root concentrate 50 mg, Boswellia extract 125 mg, turmeric root extract 50 mg, cayenne 40 m H.U. 50 mg, and hyaluronic acid 4 mg in three divided doses daily for 8 weeks reduces joint pain severity by 37% compared to only 16% with placebo. However, it does not improve joint stiffness or function when compared with placebo (89560). It is unclear if these effects are due to turmeric, other ingredients, or the combination.
• Juvenile idiopathic arthritis (JIA). Although there is interest in using oral turmeric for JIA, there is insufficient reliable information about the clinical effects of turmeric for this condition.
• Knee pain. It is unclear if oral turmeric is beneficial for knee pain. Details: Clinical research in individuals with knee pain not related to existing arthritis shows that taking turmeric extract (TurmXTRA 60N; Inventia Healthcare Ltd. and Laila Nutraceuticals) 250 mg, providing 60% curcuminoids, once daily for 90 days modestly reduces pain associated with walking 80 meters when compared with placebo. The time taken to walk 80 meters and to climb nine steps was reduced by 4-5 seconds (105396).
• Lichen planus. Evidence is conflicting on whether turmeric is beneficial for lichen planus. Details: A meta-analysis of several small, heterogeneous, mostly low-quality clinical and observational studies in adults with oral lichen planus shows that oral or topical curcumin with or without corticosteroids for 2-12 weeks does not improve erythema, lesion size, or pain when compared with control (113605). Similarly, a network meta-analysis of small clinical trials in patients with oral lichen planus shows that applying topical turmeric gel does not improve symptoms, clinical resolution, clinical scores, or reduce pain when compared with other available interventions (111640). However, small individual clinical studies have shown some benefit in using turmeric for lichen planus. A small clinical study shows that taking a specific turmeric extract (Curcumin C3 Complex, Sabinsa Corporation) containing curcuminoids 6000 mg daily in three divided doses for 12 days can reduce erythema and ulceration associated with lichen planus when compared with placebo (81109). Another small clinical study shows that taking a nanocurcumin product (SinaCurcumin, ExirNanoSina) 80 mg orally once daily for 1 month reduces oral lichen planus lesion size, pain, and burning similarly to prednisolone 10 mg taken orally once daily for 1 month (104961).
• Metabolic syndrome. It is unclear if oral turmeric is beneficial for metabolic syndrome. Details: Research is conflicting on how turmeric, curcumin, and other formulations affect various measures of metabolic syndrome. Some clinical research and a meta-analysis of 13 clinical studies in patients with metabolic syndrome show that taking turmeric or curcumin decreases low-density lipoprotein (LDL) cholesterol, waist circumference by 2 cm, fasting blood glucose by 9 mg/dL, and diastolic blood pressure by 3 mmHg and increases high-density lipoprotein (HDL) cholesterol by 5 mg/dL when compared with placebo. However, other research shows that turmeric or curcumin have no effect on body weight, lipids, blood pressure, or blood glucose when compared with placebo (98999,99311,105400,109284,111347,112118). The validity of these effects is limited by high heterogeneity within the included studies and incomplete information about randomization and blinding. Studies have used turmeric, curcumin, and curcumin extract 80-2400 mg, in divided doses, daily for 4-12 weeks, nano-curcumin 80 mg daily for 12 weeks, or calebin A (CurCousin, Sabinsa), which is a constituent of turmeric, 25 mg twice daily for 3 months (98999,99311,105400,109284,111347,112118). Also, taking crude or phosphorylated curcuminoids 1 gram daily for 6 weeks does not improve sleep or reduce weight in these patients (105397).
• Migraine headache. It is unclear if oral curcumin is beneficial for migraine headache. Details: A small clinical trial in females with regular migraines shows that taking curcumin 500 mg twice daily for 8 weeks reduces the severity and duration, but not the frequency, of migraine headaches when compared with placebo. In individuals taking curcumin, the duration of headache per month was reduced by approximately 10.3 hours from baseline (107116).
• Myocardial infarction (MI). It is unclear if oral curcumin is beneficial for reducing myocardial injury following a MI. Details: Clinical research in patients with an acute MI shows that taking curcuminoids 500 mg plus piperine (Bioperine) 5 mg daily (Sami Labs) for 8 weeks does not improve ejection fraction, serum levels of cardiac troponin 1, blood pressure, levels of fasting blood glucose, or kidney function parameters when compared to placebo. However, there were some modest benefits on levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, glycated hemoglobin, and certain liver enzymes such as aspartate aminotransferase (AST) and alkaline phosphatase (ALP) (107115). The validity of this study is limited by its short duration and relatively small sample size.
• Obesity. Oral turmeric might modestly improve weight loss, although any effect is unlikely to be clinically significant. Details: Multiple meta-analyses of small, mostly low-quality clinical studies in adults with a variety of comorbid conditions show that taking various forms and doses of turmeric or curcumin results in an average weight loss of about 0.6-1 kg, a decrease in body mass index (BMI) of about 0.2-0.5 kg/m2, and a decrease in waist circumference of about 1.3 cm when compared with control (102345,111351,111352). A sub-analysis of dose and duration shows that a reduction in waist circumference only occurs with curcumin daily doses above 1000 mg, and duration of treatment longer than 8 weeks (102345).
• Oral submucous fibrosis. Small studies suggest that topical or oral curcumin might be beneficial for oral submucous fibrosis. However, the research is heterogenous with respect to outcomes, comparators, and the turmeric preparations, doses, and routes of administration utilized. Details: A meta-analysis of 3 small clinical trials shows that turmeric modestly improves mouth opening when compared with control. In addition, a systematic review of 11 studies shows that turmeric improves overall symptoms, including mouth opening, tongue protrusion, burning sensation, and cheek flexibility. However, studies were small with short duration and used variable dosing strategies. Most trials have studied oral turmeric 300-400 mg, either alone or with black pepper 100 mg or piperine 5 mg, for 3-6 months. Less commonly, turmeric was provided in lozenge form (105399). Also, a network meta-analysis suggests that the turmeric constituent curcumin with or without piperine is most the effective for reducing tongue protrusion when compared indirectly with various medical and antioxidant therapies; however, this analysis suggests that curcumin does not rank among the most effective interventions for improving mouth opening, burning sensation, or cheek flexibility (113514). Other preliminary clinical research shows that taking a specific oral product containing curcumin 300 mg and piperine 5 mg (Turmix tablets, Sanat Products), three times daily for 12 weeks, improves mouth opening, burning sensation, and tongue protrusion when compared with baseline, but not when compared with an antioxidant product containing alpha-lipoic acid, beta-carotene, copper, lycopene, selenium, and zinc. Mouth opening is further improved by concurrent use of a mouthwash (Turmix mouthwash, Sanat Products), containing 0.1% w/v turmeric extract (standardized to 95% curcumin), with thymol, eucalyptol, clove oil, mentha oil, and tea tree oil, twice daily for 12 weeks (102347). A small clinical study shows that applying topical curcumin gel (Curenext, Abbott Laboratories) 5 mg daily in 3-4 divided doses for 6 weeks, in combination with oral physical therapy, improves mouth opening similarly to using an aloe vera gel in combination with oral physical therapy. However, decreases in burning sensation are greater with aloe gel than curcumin gel (104967). It is not clear whether the gels, oral physical therapy, or the combination of both is responsible for the outcome. Finally, clinical research shows that applying a paste providing turmeric and holy basil 10 grams each, mixed in 10 mL of honey, to the oral mucosa 4 times daily for 3 months modestly improves mouth opening, tongue protrusion, and burning sensation and reduces the presence of fibrous bands when compared with taking a vitamin B supplement. There was no effect on the shape of the uvula (113325).
• Pain (acute). Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with acute musculoskeletal pain shows that taking a specific combination product containing turmeric and Boswellia serrata extracts in black sesame oil (Rhuleave-K; Arjuna Natural Private Ltd.) 1000 mg daily for 7 days is as effective as acetaminophen 1000 mg daily for pain relief, onset of pain relief, and onset of maximal pain relief (109287). This study is limited by its lack of blinding and placebo control. Additionally, the dose of acetaminophen used in this study is below the standard recommended daily dose.
• Periodontitis. There is limited evidence on the oral or topical use of turmeric or its constituent curcumin in patients with periodontitis. Details: A meta-analysis of heterogenous clinical studies in patients with chronic periodontitis suggests that use of local delivery gel products, usually turmeric 2% or a specific product containing curcumin (Curenext), modestly reduces pocket depth when compared with routine products, such as chlorhexidine. However, limited research suggests that curcumin products do not affect plaque or gingivitis measures, and curcumin irrigation does not affect pocket depth based on limited research (107108). A small preliminary clinical study in patients with severe chronic periodontitis shows that placing curcumin gel 2 mg on one side of the mouth along with scaling and root planing (SRP) reduces plaque and probing pocket depth, but not gingival index, when compared with SRP alone (101339). The use of oral curcumin has also been investigated. A small clinical trial in patients with gingivitis and mild periodontitis shows that taking a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina) 80 mg daily after breakfast for 4 weeks reduces the severity of gingivitis and gingival bleeding, but not plaque, when compared with placebo (104146).
• Physical performance. It is unclear if oral turmeric may be beneficial for improving physical performance in older adults. Details: A very small clinical study in moderately functioning, sedentary adults over age 65 with low-grade chronic inflammation shows that that taking a specific turmeric extract (Curcumin C3 Complex, Sabinsa Corporation) 500 mg twice daily for 12 weeks does not improve measures of physical function, walking speed, or muscle strength when compared with placebo (111357). However, this study may have been inadequately powered to detect any possible differences between groups.
• Polycystic ovary syndrome (PCOS). Small clinical studies suggest that oral curcumin may improve some metabolic parameters in patients with PCOS, but these improvements may not be considered clinically significant. Details: Clinical research in patients with PCOS shows that taking curcumin 500 mg one to three times daily for 6-12 weeks improves some metabolic parameters (104968,105394,106795). Conversely, a small clinical study in patients aged 18 to 45 with PCOS in Iran shows that taking curcumin 1000 mg daily for 12 weeks modestly reduces fasting glucose but does not improve other metabolic parameters when compared with placebo. Taking curcumin also did not improve testosterone levels or hirsutism scores (111355). Meta-analyses show that taking curcumin modestly decreases body mass index (BMI) and improves measures of glycemic control, including fasting glucose and insulin resistance, and levels of total cholesterol when compared with placebo or metformin alone. However, effects on high-density lipoprotein (HDL) cholesterol levels were mixed and there was no effect on low-density lipoprotein (LDL) cholesterol or triglyceride levels (105394,106795,110219). Other preliminary clinical research shows that taking curcumin decreases plasma dehydroepiandrosterone and fasting plasma glucose levels when compared with placebo (104968). Some clinical research also shows that taking nano-curcumin (SinaCurcumin, ExirNanoSina) 80 mg daily for 3 months is beneficial in patients already taking metformin 1500 mg daily. Taking curcumin had modest beneficial effects on fasting insulin and insulin resistance, as well as levels of testosterone, LDL cholesterol, HDL cholesterol, and triglycerides, when compared with metformin alone. There was no effect of curcumin on body weight, fasting blood glucose, or other hormones (106060).
• Postoperative pain. Small clinical studies suggest that oral curcumin, a constituent of turmeric, may modestly reduce pain in various postoperative recovery settings. Details: One small clinical study in patients undergoing laparoscopic cholecystectomy shows that taking curcumin 2 grams daily reduces postoperative pain, fatigue, and the need for analgesics by the second postoperative week when compared with placebo (81099). In patients undergoing surgery for inguinal hernia and/or hydrocele, taking curcumin 1.2 grams daily for 5 days reduces inflammation and tenderness by the sixth postoperative day when compared with placebo (81206). Curcumin was taken in 3-4 divided doses daily in these studies. Finally, taking a single dose of curcumin 200 mg after surgical removal of impacted third molars modestly reduces acute postoperative pain when compared with taking mefenamic acid 500 mg (99305).
• Premenstrual syndrome (PMS). It is unclear if oral turmeric may be beneficial for improving symptoms of PMS. Details: Some preliminary clinical research in patients with PMS shows that taking curcumin 100 mg twice daily, starting 7 days prior to menstruation and continuing for 3 days after menstruation, improves physical, behavioral, and mood symptoms, as well as overall severity of symptoms, when compared with placebo (97433). Conversely, in university students aged 18 to 24 in Iran with mild to severe PMS and primary dysmenorrhea, a clinical study shows that taking a specific combination product containing curcumin 500 mg plus extract from black pepper 5 mg (C3 Complex, Sami Labs) daily, starting 7 days prior to menstruation and continuing for 3 days after menstruation for 3 consecutive menstrual cycles, does not improve the severity of symptoms when compared with placebo (106805).
• Prostate cancer. It is unclear if oral turmeric is beneficial for the prevention or treatment of prostate cancer. Details: One small clinical study shows that taking curcumin 1.8 grams orally three times daily for 7 days, starting 4 days prior to docetaxel and prednisone treatment and continuing for up to 6 cycles, reduces PSA levels by at least half in 59% of patients when compared to baseline. Also, all patients with measurable lesions showed at least stable disease after treatment, and 40% of patients showed partial response when compared with baseline (96132). It is unclear if the addition of turmeric is beneficial when compared with docetaxel and prednisone alone. In contrast, an additional small clinical trial shows that taking curcumin 6 grams daily for 7 days every 3 weeks, starting four days before docetaxel, does not improve PSA levels or progression-free or overall survival when compared with docetaxel alone (105392).
• Psoriasis. Evidence is limited to one small study of topical use in patients with scalp psoriasis. Details: Preliminary clinical research in adults with scalp psoriasis shows that applying a tonic of turmeric to the scalp twice daily for 9 weeks modestly improves overall symptoms and quality of life when compared with a placebo tonic (97429).
• Quality of life. Some preliminary clinical research suggests that oral curcumin might improve quality of life in patients with various chronic conditions. Details: Small or low-quality clinical trials in various patient populations show that taking curcumin improves at least some measures of quality of life when compared with placebo. Research has been conducted in patients with cancer, sulfur mustard-induced chronic pruritus, benign prostatic hyperplasia (BPH), or irritable bowel syndrome (IBS). Studies have evaluated curcumin 2250 mg once daily for 6 months, a specific combination product (C3 Complex, Sami Labs LTD) containing curcumin 500-1000 mg plus piperine (Bioperine) daily for 4-9 weeks, or a combination product (CU-FEO, Alfa Wasserman S.p.A.) containing curcumin 42 mg and fennel essential oil 25 mg per capsule twice daily for 60 days (81120,81176,97422,106799,107109,107111). Also, in patients with scalp psoriasis, applying a tonic of turmeric to the scalp twice daily for 9 weeks modestly improves quality of life when compared with a placebo tonic (97429).
• Radiation dermatitis. It is unclear if oral or topical turmeric is beneficial for reducing the severity of radiation dermatitis. Details: A meta-analysis of 4 clinical studies in patients with breast cancer shows that taking curcumin 500-2000 mg three times daily for 3-7 weeks or applying curcumin gel 500 mg three times daily for 7 weeks reduces the radiation dermatitis severity score by about 0.5 points (on a 4-point scale) when compared with placebo or other control (111354). The validity of this analysis is limited by the heterogeneity of the included studies. However, a small clinical study in patients with breast cancer shows that taking nanocurcumin 80 mg twice daily during and for up to 2 weeks after treatment does not reduce skin reaction severity overall, but does modestly reduce pain, when compared with taking placebo. Also, there was a small reduction in skin reaction severity near the end of the study. All patients also used aloe vera leaf as part of the hospital protocol (109281). Another small preliminary clinical study in head and neck cancer patients shows that a specific cream (Vicco turmeric cream, Vicco Laboratories) containing turmeric and sandalwood oil, applied 5 times daily during radiation therapy, seems to reduce frequency and severity of radiation dermatitis when compared with baby oil (99307).
• Radiation proctopathy. It is unclear if oral turmeric is beneficial for preventing proctitis or cystitis in patients receiving radiotherapy for prostate cancer. Details: A small clinical study in patients with prostate cancer shows that taking a specific nanocurcumin product (SinaCurcumin, ExirNanoSina) 120 mg daily, for 3 days before and also during a course of radiotherapy, does not reduce the occurrence of proctitis or cystitis when compared with placebo (100259). This study may have been underpowered to detect small treatment effects.
• Respiratory tract infections. Although there is interest in using oral turmeric for various respiratory tract infections, including bronchitis and the common cold, it has not been clinically evaluated.
• Rheumatoid arthritis (RA). Small clinical studies suggest that oral curcumin, a constituent of turmeric, may modestly improve some symptoms of RA. Details: Meta-analyses of small clinical trials in patients with RA show that taking curcumin alone or with other treatments modestly reduces overall RA symptoms, pain, and markers of inflammation when compared with control groups, including placebo or other treatments. However, some research shows that there is no beneficial effect on tender or swollen joint count from the limited available clinical research (109280,111358), while other research shows that there is a benefit (112117). Clinical studies have evaluated curcumin 120-1200 mg daily for 2 weeks to 3 months (11149,18205,96129). The validity of these findings is limited by the small size of the studies, and in some cases, the lack of a comparator group.
• Sarcopenia. Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in elderly patients with sarcopenia shows that taking a specific slow-release product containing turmeric, protein, carbohydrate, and fiber (Cureit, Aurea Biolabs), 500 mg orally daily for 3 months, increases handgrip strength by about 1% and distance walked before feeling tired by about 6% when compared with placebo. It also increases weightlifting capacity by about 6% from baseline, compared with a 5% decrease from baseline in those taking placebo (104973). It is unclear whether these small changes are clinically meaningful.
• Schizophrenia. Although there is interest in using oral turmeric for improving cognitive function in patients with schizophrenia, there is insufficient reliable information about the clinical effects of turmeric for this use.
• Sepsis. It is unclear if oral curcumin, a constituent of turmeric, is beneficial in patients with sepsis. Details: A small clinical trial in patients admitted to the intensive care unit (ICU) with sepsis shows that a specific nanoparticle formulation of curcumin (SinaCurcumin, ExirNanoSina), 80 mg dissolved in water and administered via gastric tube following lavage twice daily for 10 days does not affect length of ICU stay, Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, blood pressure, or heart rate when compared with placebo (108873).
• Smoking cessation. Oral turmeric has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with a history of smoking 5 or more cigarettes daily for at least 3 years shows that taking a specific combination product containing turmeric 50 mg, ashwagandha, Indian gooseberry, tribulus, bacopa, Albizia lebbeck, licorice, clove, ginger, cowhage, and holy basil (Smotect, Smotect India) daily for 3 months reduces the number of cigarettes smoked by approximately 3 per day when compared with placebo. This product also reduces levels of alveolar carbon monoxide and carboxyhemoglobin but does not improve lung capacity (112115). However, only data from patients who completed treatment were analyzed, which limits the validity of this study. It is unclear if these effects are due to turmeric, other ingredients, or the combination.
• Stress. It is unclear if oral turmeric is beneficial for reducing occupational stress in healthy adults. Details: A small clinical trial in healthy adults with occupational stress-related anxiety and fatigue shows that taking a specific type of turmeric (CurQfen, Akay Flavours and Aromatics Pvt Ltd.) that contains fenugreek dietary fiber for improved bioavailability at a dose of 500 mg twice daily for 30 days reduces stress and fatigue and improves quality of life when compared with placebo, and also when compared with a standard curcumin supplement with lower bioavailability (99308).
• Stroke. It is unclear if oral turmeric is beneficial for stroke. Details: A small clinical study conducted in Iran in adults with a recent ischemic stroke shows that taking curcumin 500 mg and piperine, a pepper constituent, 5 mg (Sami Lans, India) daily for 12 weeks reduces carotid intima-media thickness, triglycerides, total cholesterol, and systolic and diastolic blood pressure, but does not improve low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or quality-of-life indicators when compared with placebo (113601). The validity of this study is limited by the lack of statistical adjustment for multiple comparisons which can lead studies to erroneously show differences between treatment groups.
• Systemic lupus erythematosus (SLE). There is limited evidence on the oral use of turmeric in adults with lupus nephritis. Details: Preliminary clinical research in adults with lupus nephritis shows that taking turmeric 1.5 grams daily in three divided doses for 3 months reduces systolic blood pressure and improves kidney function when compared to baseline (81104). The validity of this finding is limited by the lack of a comparator group.
• Tuberculosis. It is unclear if oral turmeric is beneficial in patients receiving treatment for tuberculosis. Details: A small clinical study in adults receiving antituberculosis treatment shows that taking a formulation containing turmeric 0.5 grams and Tinospora cordifolia 0.5 grams twice daily for 4 months can reduce levels of Mycobacterium tuberculosis in the sputum and improve lesion healing when compared with antituberculosis treatment alone. Also, liver toxicity associated with the antituberculosis treatment seems to be reduced when administered with this formulation (80424). It is unclear if these effects are due to turmeric, Tinospora cordifolia, or the combination.
• Ulcerative colitis. It is unclear if oral or rectal turmeric, or its constituent, curcumin, is beneficial in adults with ulcerative colitis. Details: Although two small clinical studies in adults with ulcerative colitis show that taking oral turmeric extract 2-3 grams daily for 1-6 months improves the rate of remission and reduces relapse rate (79966,97423), a meta-analysis of these studies and one additional clinical study shows that turmeric does not improve remission rates when compared with placebo (99000). A specific product (Cur-Cure, Bara Herbs Inc) was used in some of these studies. Reasons for the conflicting findings are unclear, but may be due to small patient populations, concerns about blinding, and the inclusion of patients who were also taking immunomodulating drugs. It may also be due to differences in how a study measures remission. A meta-analysis of small clinical studies in patients with mild to moderate ulcerative colitis shows that adding oral curcumin 0.5-3 grams daily to standard treatment for 1-6 months may improve clinical remission rates, but not endoscopic remission rates, when compared with placebo (108872). However, the validity of this finding is limited by the small number of studies that evaluated endoscopic remission. A small clinical study shows that administering an enema form of turmeric extract (NCB-02, Himalaya Drug Company) as 20 mL, containing turmeric extract 140 mg, daily for 8 weeks increases response rate from 50% to about 93% and increases remission rate from about 31% to 71% when compared with placebo in patients with active ulcerative colitis. However, patients using the turmeric extract enema for shorter durations did not improve when compared with placebo (89729). Turmeric has also been investigated in combination with the Mediterranean diet. A small clinical trial shows that taking curcumin (VeNatura Curcumin Supplement) 800 mg twice daily while following the Mediterranean diet for 8 weeks is no more effective for improving ulcerative colitis symptom severity than following the Mediterranean diet without supplemental curcumin (113339).
• Uveitis. It is unclear if oral curcumin is beneficial for uveitis. Details: Observational research in patients with acute non-infectious uveitic macular edema shows that taking a specific hydrophilic curcumin product (Cucrcuwin, Diabec, Alfa Intes) 60 mg twice daily for 6 months, in conjunction with standard corticosteroid treatment, and then alone for an additional 6 months, modestly improves best corrected visual acuity, but not macular thickness or intraocular pressure, when compared with standard treatment alone for 6 months (107110).
• Wound healing. Although there is interest in using topical turmeric for wound healing, there is insufficient reliable information about the clinical effects of turmeric for this condition. More evidence is needed to rate turmeric for these uses.

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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)

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

POSSIBLY SAFE ...when black pepper oil is applied topically. Black pepper oil is nonirritating to the skin and is generally well tolerated (11). ...when black pepper oil is inhaled through the nose or as a vapor through the mouth, short-term. Black pepper oil as a vapor or as an olfactory stimulant has been used with apparent safety in clinical studies for up to 3 days and 30 days, respectively (29159,29160,29161,90502). There is insufficient reliable information available about the safety of black pepper when used orally in medicinal amounts.

CHILDREN: LIKELY SAFE
when used orally in amounts commonly found in foods (11).

CHILDREN: POSSIBLY UNSAFE
when used orally in large amounts. Fatal cases of pepper aspiration have been reported in some patients (5619,5620). There is insufficient reliable information available about the safety of topical pepper oil when used in children.

PREGNANCY: LIKELY SAFE
when used orally in amounts commonly found in foods (11).

PREGNANCY: LIKELY UNSAFE
when used orally in large amounts. Black pepper might have abortifacient effects (11,19); contraindicated. There is insufficient reliable information available about the safety of topical pepper when used during pregnancy.

LACTATION: LIKELY SAFE
when used orally in amounts commonly found in foods (11). There is insufficient reliable information available about the safety of black pepper when used in medicinal amounts during breast-feeding.

(Read more about BLACK PEPPER)

LIKELY SAFE ...when used in food amounts. Cucumbers are a common food source (103382,103385). ...when the extract, fruit, fruit extract, fruit water, juice, seed extract, and seed oil are used topically and appropriately. These ingredients have been shown to be safely used in cosmetic products in levels of 0.4% to 3% (103382,103395).

POSSIBLY SAFE ...when cucumber extract or cucumber seed extract is used orally and appropriately. A specific cucumber extract (Q-Actin) has been used with apparent safety in doses of up to 10 mg twice daily for 6 months (103385). Cucumber seed extract has been used with apparent safety in doses of up to 500 mg daily for 6 weeks (103386). There isn't enough reliable information to know if other cucumber products are safe to use in amounts greater than those found in food.

PREGNANCY AND LACTATION:
There is insufficient reliable information available about the safety of cucumber in amounts greater than those found in foods; avoid using.

(Read more about CUCUMBER)

LIKELY SAFE ...when consumed in amounts commonly found in foods. Hops extract and hops oil have Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when hops extract and hops-derived bitter acids are used orally and appropriately for medicinal purposes, short-term. Hops extract has been used with apparent safety in doses of up to 300 mg daily for 2-3 months. Hops-derived bitter acids have been used with apparent safety at a dose of 35 mg daily for 3 months (12,55338,55370,102899,105953,107813).

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

(Read more about HOPS)

LIKELY SAFE ...when used orally and appropriately, short-term. Turmeric products providing up to 8 grams of curcumin have been safely used for up to 2 months (10453,11144,11150,17953,79085,89720,89721,89724,89728,101347)(81036,101349,107110,107116,107117,107118,107121,109278,109283). Turmeric in doses up to 3 grams daily has been used with apparent safety for up to 3 months (102350,104146,104148,113357). ...when used topically and appropriately (11148).

POSSIBLY SAFE ...when used as an enema, short-term. Turmeric extract in water has been used as a daily enema for up to 8 weeks (89729). ...when used topically as a mouthwash, short-term. A mouthwash containing 0.05% turmeric extract and 0.05% eugenol has been used safely twice daily for up to 21 days (89723).

PREGNANCY: LIKELY SAFE
when used orally in amounts commonly found in food.

PREGNANCY: LIKELY UNSAFE
when used orally in medicinal amounts; turmeric might stimulate the uterus and increase menstrual flow (12).

LACTATION: LIKELY SAFE
when used orally in amounts commonly found in food. There is insufficient reliable information available about the safety of using turmeric in medicinal amounts during lactation.

(Read more about TURMERIC)

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)

AMOXICILLIN (Amoxil, Trimox) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase the effects and side effects of amoxicillin.  Details Animal research shows that taking piperine, a constituent of black pepper, with amoxicillin increases plasma levels of amoxicillin (29269). This has not been reported in humans.

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase the risk of bleeding when taken with antiplatelet or anticoagulant drugs.  Details In vitro research shows that piperine, a constituent of black pepper, seems to inhibit platelet aggregation (29206). This has not been reported in humans.

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase the risk of hypoglycemia when taken with antidiabetes drugs.  Details Animal research shows that piperine, a constituent of black pepper, can reduce blood glucose levels (29225). Monitor blood glucose levels closely. Dose adjustments might be necessary.

ATORVASTATIN (Lipitor) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase blood levels of atorvastatin.  Details Animal research shows that taking piperine, a constituent of black pepper, 35 mg/kg can increase the maximum serum concentration of atorvastatin three-fold (104188). This has not been reported in humans.

CARBAMAZEPINE (Tegretol) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, black pepper might increase blood levels of carbamazepine, potentially increasing the effects and side effects of carbamazepine.  Details One clinical study in patients taking carbamazepine 300 mg or 500 mg twice daily shows that taking a single 20 mg dose of purified piperine, a constituent of black pepper, increases carbamazepine levels. Piperine may increase carbamazepine absorption by increasing blood flow to the GI tract, increasing the surface area of the small intestine, or inhibiting cytochrome P450 3A4 (CYP3A4) in the gut wall. Absorption was significantly increased by 7-10 mcg/mL/hour. The time to eliminate carbamazepine was also increased by 4-8 hours. Although carbamazepine levels were increased, this did not appear to increase side effects (16833). In vitro research also shows that piperine can increase carbamazepine levels by 11% in a time-dependent manner (103819).

CYCLOSPORINE (Neoral, Sandimmune) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase the effects and side effects of cyclosporine.  Details In vitro research shows that piperine, a constituent of black pepper, increases the bioavailability of cyclosporine (29282). This has not been reported in humans.

CYTOCHROME P450 1A1 (CYP1A1) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase levels of drugs metabolized by CYP1A1.  Details In vitro research suggests that piperine, a constituent of black pepper, inhibits CYP1A1 (29213). This has not been reported in humans.

CYTOCHROME P450 2B1 (CYP2B1) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase levels of drugs metabolized by CYP2B1.  Details In vitro research suggests that piperine, a constituent of black pepper, inhibits CYP2B1 (29332). This has not been reported in humans.

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase levels of drugs metabolized by CYP2D6.  Details In vitro research suggests that some constituents of black pepper inhibit CYP2D6 (29207,29212,38375). This has not been reported in humans.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase levels of drugs metabolized by CYP3A4.  Details In vitro research shows that piperine, a constituent of black pepper, as well as the pepper fruit seem to inhibit CYP3A4 (14375,29212). This has not been reported in humans.

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, black pepper might increase blood levels of lithium due to its diuretic effects. The dose of lithium might need to be reduced.  Details Black pepper is thought to have diuretic properties (11).

NEVIRAPINE (Viramune) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = D Black pepper might increase blood levels of nevirapine.  Details Clinical research shows that piperine, a constituent of black pepper, increases the plasma concentration of nevirapine. However, no adverse effects were observed in this study (29209).

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase levels of P-glycoprotein substrates.  Details In vitro research shows that piperine, a constituent of black pepper, seems to inhibit P-glycoprotein (14375,29281,29283).

PENTOBARBITAL (Nembutal) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, black pepper might increase the sedative effects of pentobarbital.  Details Animal research shows that piperine, a constituent of black pepper, increases pentobarbital-induced sleeping time (29214).

PHENYTOIN (Dilantin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Black pepper might increase blood levels of phenytoin.  Details Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption, slow elimination, and increase levels of phenytoin (537,14442). Taking a single dose of black pepper 1 gram along with phenytoin seems to double the serum concentration of phenytoin (14375). Consuming a soup with black pepper providing piperine 44 mg/200 mL of soup along with phenytoin also seems to increase phenytoin levels when compared with consuming the same soup without black pepper (14442).

PROPRANOLOL (Inderal) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Black pepper might increase blood levels of propranolol.  Details Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of propranolol (538).

RIFAMPIN (Rifadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Black pepper might increase blood levels of rifampin.  Details Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and serum levels of rifampin (14375,29284).

THEOPHYLLINE Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Black pepper might increase blood levels of theophylline.  Details Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of theophylline (538).

(Read more about BLACK PEPPER)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, cucumber seed might have additive effects with antidiabetes drugs and may increase the risk of hypoglycemia.  Details Animal research shows that cucumber seed extract can decrease blood glucose levels (103391). Monitor blood glucose levels closely.

(Read more about CUCUMBER)

CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of hops with sedative drugs might cause additive sedation.  Details Some animal research shows that hops has sedative effects (55415,55340,105930).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Hops extract does not seem to affect the metabolism of CYP1A2 substrates.  Details In vitro research suggests that flavonoid constituents of hops inhibit CYP1A2 enzyme activity (10686). However, a pharmacokinetic study in healthy postmenopausal patients shows that taking a standardized extract of spent hops containing prenylated phenols, as 59.5 mg twice daily for 2 weeks, does not affect levels of caffeine, a CYP1A2 probe substrate (105954).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, hops extract might alter metabolism of CYP3A4 substrates; however, this effect may not be clinically significant.  Details Animal research suggests that specific constituents of hops, called lupulones, can induce hepatic CYP3A4 enzyme activity (55325). However, a pharmacokinetic study in healthy postmenopausal patients with normal metabolism shows that taking a standardized extract of spent hops containing prenylated phenols, as 59.5 mg twice daily for 2 weeks, decreases the concentration of alprazolam, a CYP3A4 probe substrate, by 7.6%. This reduction is unlikely to be clinically relevant (105954).

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of large amounts of hops might interfere with hormone replacement therapy due to competition for estrogen receptors.  Details In vitro research suggests that certain hops constituents can competitively bind to estrogen receptors (3701,10684,10685). However, most hops extracts contain very small amounts of these constituents (105930).

(Read more about HOPS)

ALKYLATING AGENTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.  Details In vitro research suggests that curcumin, a constituent of turmeric, inhibits mechlorethamine-induced apoptosis of breast cancer cells by up to 70%. Also, animal research shows that curcumin inhibits cyclophosphamide-induced tumor regression (96126). However, some in vitro research shows that curcumin does not affect the apoptosis capacity of etoposide. Also, other laboratory research suggests that curcumin might augment the cytotoxic effects of alkylating agents. Reasons for the discrepancies may relate to the dose of curcumin and the specific chemotherapeutic agent. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects (96125). More evidence is needed to determine what effect, if any, turmeric might have on alkylating agents.

AMLODIPINE (Norvasc) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Taking turmeric with amlodipine may increase levels of amlodipine.  Details Animal research shows that giving amlodipine 1 mg/kg as a single dose following the use of turmeric extract 200 mg/kg daily for 2 weeks increases the maximum concentration and area under the curve by 53% and 56%, respectively, when compared with amlodipine alone (107113). Additional animal research shows that taking amlodipine 1 mg/kg with a curcumin 2 mg/kg pretreatment for 10 days increases the maximum concentration and area under the curve by about 2-fold when compared with amlodipine alone (103099).

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Turmeric may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs. However, research is conflicting.  Details Curcumin, a constituent of turmeric, has demonstrated antiplatelet effects in vitro (11143,81204,81271). Furthermore, two case reports have found that taking turmeric along with warfarin or fluindione was associated with an increased international normalized ratio (INR) (89718,100906). However, one clinical study in healthy volunteers shows that taking curcumin 500 mg daily for 3 weeks, alone or with aspirin 100 mg, does not increase antiplatelet effects or bleeding risk (96137). It is possible that the dose of turmeric used in this study was too low to produce a notable effect.

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking turmeric with antidiabetes drugs might increase the risk of hypoglycemia.  Details Animal research and case reports suggest that curcumin, a turmeric constituent, can reduce blood glucose levels in patients with diabetes (79692,79984,80155,80313,80315,80476,80553,81048,81219). Furthermore, clinical research in adults with type 2 diabetes shows that taking curcumin 475 mg daily for 10 days prior to taking glyburide 5 mg decreased postprandial glucose levels for up to 24 hours when compared with glyburide alone, despite the lack of a significant pharmacokinetic interaction (96133). Another clinical study in patients with diabetes on hemodialysis shows that taking curcumin 80 mg daily for 12 weeks can reduce blood glucose levels when compared with placebo (104149).

ANTITUMOR ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.  Details In vitro and animal research shows that curcumin, a constituent of turmeric, inhibits doxorubicin-induced apoptosis of breast cancer cells by up to 65% (96126). However, curcumin does not seem to affect the apoptosis capacity of daunorubicin. In fact, some research shows that curcumin might augment the cytotoxic effects of antitumor antibiotics, increasing their effectiveness. Reasons for the discrepancies may relate to the dose of curcumin and the chemotherapeutic agent. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects (96125). More evidence is needed to determine what effects, if any, antioxidants such as turmeric have on antitumor antibiotics.

CYTOCHROME P450 1A1 (CYP1A1) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase or decrease levels of drugs metabolized by CYP1A1. However, research is conflicting.  Details Most in vitro and animal research suggests that the turmeric constituent, curcumin, INHIBITS CYP1A1, primarily in the liver (15823,21495,80876,81411). However, some evidence from in vitro research suggests that curcumin may INDUCE CYP1A1 in the intestines (21500).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase levels of drugs metabolized by CYP1A2. However, research is conflicting.  Details In vitro and animal research show that the turmeric constituent, curcumin, inhibits CYP1A2 (15823,21497,81304). However, other in vitro research suggests that curcumin does not significantly affect CYP1A2 (22000).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric might increase levels of drugs metabolized by CYP3A4.  Details In vitro and animal research show that turmeric and its constituents curcumin and curcuminoids inhibit CYP3A4 (21497,21498,21499). Also, 8 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking turmeric and cancer medications that are CYP3A4 substrates, including everolimus, ruxolitinib, ibrutinib, and palbociclib, and bortezomib (111644). In another case report, a transplant patient presented with acute nephrotoxicity and elevated tacrolimus levels after consuming turmeric powder at a dose of 15 or more spoonfuls daily for ten days prior. It was thought that turmeric increased levels of tacrolimus due to CYP3A4 inhibition (93544). Conversely, other in vitro research suggests that turmeric induces CYP3A4 activity, leading to reduced levels of CYP3A4 substrates (111404). However, this interaction has not been reported in humans.

DOCETAXEL (Taxotere) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase blood levels of oral docetaxel.  Details Animal research suggests that the turmeric constituent, curcumin, enhances the oral bioavailability of docetaxel (80999). However, the significance of this interaction is unclear, as this drug is typically administered intravenously in clinical settings.

ESTROGENS Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, large amounts of turmeric might interfere with hormone replacement therapy through competition for estrogen receptors.  Details In vitro research shows that curcumin, a constituent of turmeric, displaces the binding of estrogen to its receptors (21486).

GLYBURIDE (Diabeta, others) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking turmeric and glyburide in combination might increase the risk of hypoglycemia.  Details Clinical research shows that taking curcumin 475 mg daily for 10 days prior to taking glyburide 5 mg increases blood levels of glyburide by 12% at 2 hours after the dose in patients with type 2 diabetes. While maximal blood concentrations of glyburide were not affected, turmeric modestly decreased postprandial glucose levels for up to 24 hours when compared to glyburide alone, possibly due to the hypoglycemic effect of turmeric demonstrated in animal research (96133).

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase the risk of liver damage when taken with hepatotoxic drugs.  Details There is concern that turmeric might cause hepatotoxicity, especially when highly bioavailable formulations are used in high doses (103633,107122,109288,110221).

LOSARTAN (Cozaar) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase the effects of losartan.  Details Research in hypertensive rats shows that taking turmeric can increase the hypotensive effects of losartan (110897).

METHOTREXATE (Trexall, others) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might have additive effects when used with hepatotoxic drugs such as methotrexate.  Details In one case report, a 39-year-old female taking methotrexate, turmeric, and linseed oil developed hepatotoxicity (111644).

NORFLOXACIN (Noroxin) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase the effects and adverse effects of norfloxacin.  Details Animal research shows that taking curcumin, a turmeric constituent, can increase blood levels of orally administered norfloxacin (80863).

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase blood levels of OATP4C1 substrates.  Details In vitro research shows that the turmeric constituent curcumin competitively inhibits OATP4C1 transport. This transporter is expressed in the kidney and facilitates the renal excretion of certain drugs (113337). Theoretically, taking turmeric might decrease renal excretion of OATP substrates.

P-GLYCOPROTEIN SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might increase the absorption of P-glycoprotein substrates.  Details In vitro and animal research shows that curcuminoids and other constituents found in turmeric can inhibit P-glycoprotein expression and activity (21472,21473,21474,21475,21476,21477,21478,21479,21480)(21482,21484,111644).

PACLITAXEL (Abraxane, Onxol) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, turmeric might alter blood levels of paclitaxel, although any effect may not be clinically relevant.  Details Clinical research in adults with breast cancer receiving intravenous paclitaxel suggests that taking turmeric may modestly alter paclitaxel pharmacokinetics. Patients received paclitaxel on day 1, followed by either no treatment or turmeric 2 grams daily from days 2-22. Pharmacokinetic modeling suggests that turmeric reduces the maximum concentration and area under the curve of paclitaxel by 12.1% and 7.7%, respectively. However, these changes are not likely to be considered clinically relevant (108876). Conversely, animal research suggests that curcumin, a constituent of turmeric, enhances the oral bioavailability of paclitaxel (22005). However, the significance of this interaction is unclear, as this drug is typically administered intravenously in clinical settings.

SULFASALAZINE (Azulfidine) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Turmeric might increase the effects and adverse effects of sulfasalazine.  Details Clinical research shows that taking the turmeric constituent, curcumin, can increase blood levels of sulfasalazine by 3.2-fold (81131).

TACROLIMUS (Prograf) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric might increase the effects and adverse effects of tacrolimus.  Details In one case report, a transplant patient presented with acute nephrotoxicity and elevated tacrolimus levels of 29 ng/mL. The patient previously had tacrolimus levels within the therapeutic range at 9.7 ng/mL. Ten days prior to presenting at the emergency room the patient started consumption of turmeric powder at a dose of 15 or more spoonfuls daily. It was thought that turmeric increased levels of tacrolimus due to cytochrome P450 3A4 (CYP3A4) inhibition (93544). In vitro and animal research show that turmeric and its constituent curcumin inhibit CYP3A4 (21497,21498,21499).

TALINOLOL Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Turmeric may reduce the absorption of talinolol in some situations.  Details Clinical research shows that taking curcumin for 6 days decreases the bioavailability of talinolol when taken together on the seventh day (80079). The clinical significance of this effect is unclear.

TAMOXIFEN (Nolvadex) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, turmeric might reduce the levels and clinical effects of tamoxifen.  Details In a small clinical trial in patients with breast cancer taking tamoxifen 20-30 mg daily, adding curcumin 1200 mg plus piperine 10 mg three times daily reduces the 24-hour area under the curve of tamoxifen and the active metabolite endoxifen by 12.8% and 12.4%, respectively, as well as the maximum concentrations of tamoxifen, when compared with tamoxifen alone. However, in the absence of piperine, the area under the curve for endoxifen and the maximum concentration of tamoxifen were not significantly reduced. Effects were most pronounced in patients who were extensive cytochrome P450 (CYP) 2D6 metabolizers (107123).

TOPOISOMERASE I INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric has antioxidant effects. There is some concern that this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.  Details In vitro research shows that curcumin, a constituent of turmeric, inhibits camptothecin-induced apoptosis of breast cancer cells by up to 71% (96126). However, other in vitro research shows that curcumin augments the cytotoxic effects of camptothecin. Reasons for the discrepancies may relate to the dose of curcumin and the chemotherapeutic agents. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects (96125). More evidence is needed to determine what effect, if any, turmeric might have.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Turmeric might increase the risk of bleeding with warfarin.  Details One case of increased international normalized ratio (INR) has been reported for a patient taking warfarin who began taking turmeric. Prior to taking turmeric, the patient had stable INR measurements. Within a few weeks of starting turmeric supplementation, the patient's INR increased to 10 (100906). Additionally, curcumin, the active constituent in turmeric, has demonstrated antiplatelet effects in vitro (11143,81204,81271), which may produce additive effects when taken with warfarin.

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

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

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

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

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

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

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

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

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

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

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

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

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

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General ...Orally, black pepper seems to be well tolerated when used in the amounts found in food or when taken as a medicine as a single dose. Topically and as aromatherapy, black pepper oil seems to be well tolerated.
Most Common Adverse Effects:
Orally: Burning aftertaste, dyspepsia, and reduced taste perception.
Inhalation: Cough.
Serious Adverse Effects (Rare):
Orally: Allergic reaction in sensitive individuals.

Gastrointestinal ...Orally, black pepper can cause a burning aftertaste (5619) and dyspepsia (38061). Single and repeated application of piperine, the active constituent in black pepper, to the tongue and oral cavity can decrease taste perception (29267). By intragastric route, black pepper 1.5 grams has been reported to cause gastrointestinal microbleeds (29164). It is not clear if such an effect would occur with oral administration.

Immunologic ...In one case report, a 17-month-old male developed hives, red eyes, facial swelling, and a severe cough following consumption of a sauce containing multiple ingredients. Allergen skin tests were positive to both black pepper and cayenne, which were found in the sauce (93947).

Ocular/Otic ...Topically, ground black pepper can cause redness of the eyes and swelling of the eyelids (5619).

Pulmonary/Respiratory ...When inhaled through the nose as an olfactory stimulant, black pepper oil has been reported to cause cough in one clinical trial (29162).

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General ...Orally, cucumber is well tolerated in food amounts. Cucumber extract and seed extract also seem to be well tolerated. Topically, the extract, fruit, fruit extract, fruit water, juice, seed extract, and seed oil of cucumber are well tolerated.
Most Common Adverse Effects:
Topically: Allergic eczema, erythema, irritation.
Serious Adverse Effects (Rare):
Orally: Anaphylaxis.

Dermatologic ...Topically, mild redness and irritation have occurred rarely (103382).

Immunologic ...Orally, anaphylaxis with dizziness, vomiting, trouble breathing, and itching, occurring 5 minutes after eating a partially peeled cucumber, has been reported in a 76-year-old woman (103382,103384).
Topically, allergic eczema related to exposure to cucumber leaves and stems has been reported in a greenhouse worker (103382,103393).

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General ...Orally, hops extract and oil are generally well tolerated when used in food amounts. Hops extract also seems to be well tolerated when used in supplemental amounts.
Most Common Adverse Effects:
Orally: Drowsiness, sedation.

Dermatologic ...Topically, allergic reactions have been reported after contact with the fresh hops plant and plant dust. Contact dermatitis is attributed to the pollen (4,12,105930).

Genitourinary ...Orally, supplements containing hops and soy have been associated with 4 cases of postmenopausal bleeding (55404). It is unclear if this effect is due to hops, soy, or the combination. Also, menstrual disturbances have been reported in female workers harvesting hops (10684,55405).

Neurologic/CNS ...Orally, hops might cause drowsiness and sedation. Historically, hops are thought to have sedative effects, since workers harvesting hops were observed to tire easily after oral contact with hop resin. The European Medicines Agency states that hops may have sedative effects; however, there is a lack of clinical research confirming that hops extract causes drowsiness and sedation (105930).

Pulmonary/Respiratory ...Occupational exposure to dust from hops, usually in combination with dust from other products, is associated with chronic respiratory symptoms such as dry cough, dyspnea, chronic bronchitis, and other occupational respiratory diseases (55333,55414).

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General ...Orally and topically, turmeric is generally well tolerated.
Most Common Adverse Effects:
Orally: Constipation, dyspepsia, diarrhea, distension, gastroesophageal reflux, nausea, and vomiting.
Topically: Curcumin, a constituent of turmeric, can cause contact urticaria and pruritus.

Cardiovascular ...Orally, a higher dose of turmeric in combination with other ingredients has been linked to atrioventricular heart block in one case report. It is unclear if turmeric caused this adverse event or if other ingredients or a contaminant were the cause. The patient had taken a combination supplement containing turmeric 1500-2250 mg, black soybean 600-900 mg, mulberry leaves, garlic, and arrowroot each about 300-450 mg, twice daily for one month before experiencing atrioventricular heart block. Heart rhythm normalized three days after discontinuation of the product. Re-administration of the product resulted in the same adverse effect (17720).

Dermatologic ...Following occupational and/or topical exposure, turmeric or its constituents curcumin, tetrahydrocurcumin, or turmeric oil, can cause allergic contact dermatitis (11146,79270,79470,79934,81410,81195). Topically, curcumin can also cause rash or contact urticaria (79985,97432,112117). In one case, a 60-year-old female, with no prior reactivity to regular oral consumption of turmeric products, developed urticaria after topical application of turmeric massage oil (97432). A case of pruritus has been reported following topical application of curcumin ointment to the scalp for the treatment of melanoma (11148). Yellow discoloration of the skin has been reported rarely in clinical research (113356). Orally, curcumin may cause pruritus, but this appears to be relatively uncommon (81163,97427,104148). Pitting edema may also occur following oral intake of turmeric extract, but the frequency of this adverse event is less common with turmeric than with ibuprofen (89720). A combination of curcumin plus fluoxetine may cause photosensitivity (89728).

Gastrointestinal ...Orally, turmeric can cause gastrointestinal adverse effects (107110,107112,112118), including constipation (81149,81163,96135,113355), flatulence and yellow, hard stools (81106,96135), nausea and vomiting (10453,17952,89720,89728,96127,96131,96135,97430,112117,112118), diarrhea or loose stool (10453,17952,18204,89720,96135,110223,112117,112118), dyspepsia (17952,89720,89721,96161,112118), gastritis (89728), distension and gastroesophageal reflux disease (18204,89720), abdominal fullness and pain (81036,89720,96161,97430), epigastric burning (81444), and tongue staining (89723).

Hepatic ...Orally, turmeric has been associated with liver damage, including non-infectious hepatitis, cholestasis, and hepatocellular liver injury. There have been at least 70 reports of liver damage associated with taking turmeric supplements for at least 2 weeks and for up to 14 months. Most cases of liver damage resolved upon discontinuation of the turmeric supplement. Sometimes, turmeric was used concomitantly with other supplements and medications (99304,102346,103094,103631,103633,103634,107122,109288,110221). The Drug-Induced Liver Injury Network (DILIN) has identified 10 cases of liver injury which were considered to be either definitely, highly likely, or probably associated with turmeric; none of these cases were associated with the use of turmeric in combination with other potentially hepatotoxic supplements. Most patients (90%) presented with hepatocellular pattern of liver injury. The median age of these case reports was 56 years and 90% identified as White. In these case reports, the carrier frequency on HLAB*35:01 was 70%, which is higher than the carrier frequency found in the general population. Of the ten patients, 5 were hospitalized and 1 died from liver injury (109288).
It is not clear if concomitant use with other supplements or medications contributes to the risk for liver damage. Many case reports did not report turmeric formulation, dosing, or duration of use (99304,103094,103631,103634,109288). However, at least 10 cases involved high doses of curcumin (250-1812.5 mg daily) and the use of highly bioavailable formulations such as phytosomal curcumin and formulations containing piperine (102346,103633,107122,109288,110221).

Neurologic/CNS ...Orally, the turmeric constituent curcumin can cause vertigo, but this effect seems to be uncommon (81163).

Psychiatric ...Orally, the turmeric constituent curcumin or a combination of curcumin and fluoxetine can cause giddiness, although this event seems to be uncommon (81206,89728).

Renal ...Orally, turmeric has been linked to one report of kidney failure, although the role of turmeric in this case is unclear. A 69-year-old male developed kidney failure related to calcium oxalate deposits in the renal tubules following supplementation with turmeric 2 grams daily for 2 years as an anti-inflammatory for pelvic pain. While turmeric is a source of dietary oxalates, pre-existing health conditions and/or chronic use of antibiotics may have contributed to the course of disease (113343).

Other ...There is a single case report of death associated with intravenous use of turmeric. However, analysis of the treatment vial suggests that the vial contained only 0.023% of the amount of curcumin listed on the label. Also, the vial had been diluted in a solution of ungraded polyethylene glycol (PEG) 40 castor oil that was contaminated with 1.25% diethylene glycol. Therefore the cause of death is unknown but is unlikely to be related to the turmeric (96136).

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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).

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