Vitamin supplements are vitamins sold with specific health claims beyond their usual physiologic function. Vitamins are micronutrients which are required in very small amounts for specific physiologic processes. Since their discovery, there has been great interest in using vitamins not just to treat deficiency diseases but also for medicinal purposes. Like everything else in natural/holistic health, the claims run the gamut in factual, scientific efficacy. A few claims are backed by scientific study, though most are simple salesmanship and even a few have been irresponsibly, dangerously extravagant.
Despite often being touted as being natural, vitamins pill ingredients are actually often synthetic. This is because "our bodies appear to absorb synthetic forms as well as they do natural forms" and because vitamin manufacturers want to add the most stable form of vitamins, and these forms are not always natural.
 Vitamin industry
The dietary supplement industry is quite large, and the biggest part of the industry is vitamin sales. Numbers are difficult to come by, as they are compiled and sold by marketing firms, but an estimate for 2012 was $32 billion dollars annually. There is much misinformation about the benefits of vitamins. This article will strive to help people make better decisions about vitamin supplementation, and help to sort out extravagant claims made by producers and marketers of vitamins.
Because of the great interest in vitamins as medications, a great deal of research has gone into investigating their safety and efficacy. However, in the US, vitamins are regulated as dietary supplements, not medications, and there are no requirement for manufacturers to prove efficacy. By definition, vitamins are needed for health. In most cases, a basic, inexpensive, "general multivitamin supplement" is sufficient for adults to remain healthy. However, there is a growing body of evidence that multivitamins are unnecessary for those without vitamin deficiencies and could even cause harm in some isolated cases. Additionally, they are often marketed for uses far beyond their basic function and in much higher doses than typically needed.
The health claims used on the bottles are intentionally vague and non-specific (phrases such as "helps support", "promotes", or "bolsters"). With further protection from the Quack Miranda Warning, non-specific ailments can be treated in non-specific ways with non-specific results.
 Efficacy and safety
 Vitamin A/beta-carotene
Vitamin A deficiencies can occur in developing nations and can lead to severe visual problems, and other conditions; with 200 million children affected by this deficiency (causing half a million deaths and another half a million cases of permanent blindness), this may be the most widespread deficiency. Beta-carotene (β-carotene), a common precursor to Vitamin A used as a supplement, has been studied as an "antioxidant" and cancer preventative. However, large, well-conducted studies have shown an increase in lung cancer in people taking these supplements. Smokers, and others at increased risk for lung cancer, saw their risk increase even more. Also, a recent study showed an increase in aggressive prostate cancers in men taking beta-carotene.
Since Vitamin A derives from beta-carotene, a carotenoid pigment, massive overdoses of either substances can turn the consumer's skin yellow or orange. Also, both substances are closely related to retinoid pigments such as form the photosensitive component of most animal eyes. Such substances are also used in medicine to treat severe skin diseases such as disfiguring acne and ichthyosis; however, they can be teratogens due to their effect on DNA, requiring careful monitoring, especially in female patients.
Unlike beta-carotene, vitamin A in retinoid form is not water soluble. Thus, serious health complications can arise from taking too much of it (c.f. Hypervitaminosis A). This is why you shouldn't eat polar bear liver.
- Vitamin B9, more commonly known as "folic acid," has been shown in several large well-controlled studies in the U.S. and China to prevent neural tube defects like spina bifida. The effect was greatest when women began taking folic acid before becoming pregnant. This has led to folate supplementation of foods in the U.S. High homocysteine levels in adults is associated with heart disease, and can be reduced by adequate folate intake, although it has not been shown that taking folic acid reduces cardiac risk.
- A deficiency of Vitamin B1, called "thiamine", can result in beriberi. In the developed world this is most commonly seen in people who have a long history of chronic alcohol or other substance abuse, and in places dependent on rice it can be largely prevented by eating it unpolished.
- A deficiency of Vitamin B2, called "riboflavin", can result in ariboflavinosis. However, riboflavin deficiency is always accompanied by deficiency of other vitamins.
- A deficiency of Vitamin B3, called "niacin", can result in pellagra (the first disease described using the modern scientific method, although it wasn't until later that they got to the cause). A lack of tryptophan, which the body converts to niacin, can have the same effect, and there is one known genetic disorder that somewhat (though not entirely) inhibits the conversion of tryptophan to niacin. Pellagra was rampant in the South well into the 20th century, but is now exceedingly rare in the developed world thanks to vitamin fortifications (a.k.a., supplementation) in food (in the US, bread and enriched rice/flour). Although the US RDA of niacin is 20 mg per day, niacin is increasingly being prescribed at therapeutic dosage levels (upwards of 1000 mg per day) as a treatment for elevated blood triglycerides. Unfortunately, large doses of niacin can result in uncomfortable flushing episodes; these can be managed by taking aspirin half an hour before taking niacin or sometimes by just eating a meal first. "No flush" versions of niacin exist, but these have been demonstrated not to have an effect on blood triglycerides and thus kinda defeat their own purpose.
- Vitamin B12 deficiency, usually from an improperly managed vegetarian or vegan diet, certain intestinal diseases, or pernicious anemia, is fairly rare, and when it exists, it must be treated (hence the word pernicious). Supplementing this vitamin in non-deficient people has not shown to have any benefit, but oral supplementation as part of a daily multivitamin may have a small effect of reducing cardiac risk in some people. "Because 10 to 30 percent of older people may malabsorb food-bound B12, it is advisable for those older than 50 years to meet their RDA mainly by consuming foods fortified with B12 or a supplement containing B12." 
- Folate, B12, and B6 are sometimes recommended for memory, but studies have failed to show any benefit in non-deficient individuals. "In view of evidence linking folate intake with neural tube defects in the fetus, it is recommended that all women capable of becoming pregnant consume 400μg from supplements or fortified foods in addition to intake of food folate from a varied diet."
- Vitamin B6 very rarely requires supplementation in the typical American diet.
 Vitamin C
Vitamin C may have the most notoriety of the commonly available vitamin supplements due to Nobel Prized-winning biochemist Linus Pauling's controversial assertions that large doses of vitamin C can prevent the common cold, a position that a) showed that even Nobel Prize winners can be wrong, egregiously wrong and b) proved to be not terribly accurate when studied, but very persistent in the journals of public opinion probably due to a lack of peer review in that forum.
Vitamin C deficiency leads to scurvy (from which the name ascorbic acid derives), which was a massive problem for early sailors. In the developed world this still needs to be accounted for when planning extended trips without access to fresh food, such as long-term submarine missions. In addition to its usual function, vitamin C is also used as a preservative for fresh fruit (especially apples, where it prevents enzymatic browning after the fruit is cut). In addition, food scientist and cookbook author Shirley Corriher, in her 1997 kitchen science book Cookwise, recommends adding vitamin C to some bread recipes to enhance gluten development.
Like vitamin E and beta-carotene, vitamin C is an antioxidant.
 Vitamin D
Vitamin D is especially important for bones. There is evidence that people who live in cooler, cloudier climates, where sun exposure is less, benefit from some supplementation.
Recent studies have also shown that Vitamin D also works as a hormone to help regulate important functions of the body. One study showed an association between excessive daytime sleepiness and low levels of Vitamin D.
 Vitamin E
According to the first edition of Harold McGee's seminal kitchen-science book On Food and Cooking, Vitamin E deficiencies are not especially common in the Western diet. Almost all cases in the developed world are completely unrelated to quality of food intake and mostly occur in very small and premature infants, in people with a specific genetic disorder that severely inhibits Vitamin E absorption, and in people who have various metabolic or gastrointestinal disorders (e.g. Crohn's disease) which result in difficulty absorbing fat from their diets. However, supplements are sold and sometimes used as skin care lotions. Vitamin E is also sometimes used as a preservative for whole grain products.
Note: "… researchers from the Cleveland Clinic found that men who took vitamin E had an increased risk of prostate cancer."
Like vitamin C and beta-carotene, vitamin E is an antioxidant.
 Vitamin K
Vitamin K (from the German Koagulationsvitamin) is used in the human body's blood clotting system. Most people get a sufficient amount of it from bacteria in the colon and from virtually any leafy vegetable such as spinach or kale, and it is not widely available as a supplement. It is contra-indicated for those on long-term anti-coagulant therapy (warfarin or similar drugs) and is useful in the treatment of ingestion of rat poison (warfarin).
Dietary minerals, such as phosphorus, magnesium, zinc, and kryptoniteDo You Believe That?, aren't classified as vitamins. However, many multivitamin supplements also include some minerals.
Several snake oil salesmen over the years have pushed mineral supplements. Sales pitches such as the audio/video/book Dead Doctors Don't Lie, colloidal silver, and more recently, Miracle Mineral Supplement, tout their mineral supplements as the cure for everything from aging to prostate cancer. Generally these high-priced mineral supplements are in some form you can't get from your local drugstore, such as colloidal suspensions, accompanied by claims that their form is much better absorbed than the normal pills are. At best, these mineral supplements will give you very expensive urine. At worst, they can cause serious side effects in sufficient quantities. For example, colloidal silver can cause the skin to become blue-gray, and excessive zinc supplementation can cause copper deficiency.
A number of substances are sold claiming to be vitamins but are not. These are often named using the "vitamin" naming convention, as in "Vitamin B17" (which is actually laetrile). A number of other substances were also once thought to be vitamins but later reclassified out of the vitamin category; occasionally one will run across these still being referred to using their old (generally pre-World War II) vitamin name, such as "Vitamin F" and "Vitamin B4". "Vitamin F" was the old name for essential fatty acids, which are essential for human nutrition but do not meet the definition of a vitamin any more than water does. "Vitamin B4" is adenine, which is no longer considered a vitamin as it is not necessary for human nutrition, although it is synthesized in the body and binds with other B vitamins. Taking any of these supplements is a waste of money, and in the case of "B17"/laetrile, can be hazardous to your health.
 National bans on vitamin supplements
 Megavitamin therapy
Megavitamin therapy is the use of large doses of vitamins, exceeding the recommended dose range, and even exceeding maximum safe dose, dose levels that have been created by scientific consensus. As such megavitamin therapy falls into the realm of quackery and alternative medicine. Megavitamin therapy is common in orthomolecular medicine and naturopathy, but is only rarely used in regular medicine for unusual genetic diseases.
The Dietary Reference Intakes (DRIs) and Tolerable Upper Intake Level (ULs) below are per day for adult males (M) and non-pregnant, non-lactating adult females (F). These values and adverse effects are taken from the Nutrient Recommendations: Dietary Reference Intakes See the original document for children's and other adult females' levels.
Depending on the vitamin, DRIs are either Recommended Dietary Allowances (RDAs) or Adequate Intakes (AIs). RDAs are the "average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%-98%) healthy people." AIs are "established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy." The Tolerable Upper Intake Level (UL) "is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects in almost all individuals." It should be noted that these levels are the total intake from all sources: dietary, Sun exposure (for vitamin D), and nutritional supplements.
It should also be noted that just because there is a UL for a given nutrient, it does not mean that there is necessarily any benefit in consuming at or near that amount. High dose antioxidant pills appear to be worse than useless (and some vitamins are antioxidants). Yes, that's right, antioxidants can hinder muscle strength. This appears to be because muscles require a certain level of oxidative stress in order to build over time.
It should be of particular concern for users of megadose mineral supplements that the consumption of mineral supplements was correlated with higher doses of minerals from food sources, particularly for calcium and magnesium.
|Micronutrient||Dietary Reference Intakes (DRI)[note 1]||Potential adverse effects below DRI[note 2]||Tolerable Upper Intake Level (UL)[note 1]||Potential adverse effects above UL[note 2]||People who have taken more than the UL and/or recommendations at/above the UL|
|Vitamin A||900 µg (M);
700 µg (F)
|Xerophthalmia, impaired embryonic development, follicular hyperkeratosis, increased risk of infectious morbidity and mortality||3000 µg||Bone mineral density loss, teratogenicity, liver abnormalities||
|Vitamin C||90 mg (M);
75 mg (F)
|Scurvy, dyspnea, edema, Sjögren's syndrome, weakness, fatigue, depression||2000 mg||Gastrointestinal disturbances, increased oxalate excretion and kidney stone formation, increased uric acid excretion, excess iron absorption, lowered vitamin B12 levels, systemic conditioning, pro-oxidant effects||
|Vitamin D||15-20 µg (M);
25-20 µg (F)
= 600-800 IU
|Rickets/osteomalacia, bone fracture, inadequate calcium absorption||100 µg (M); 100 µg (F)
|Hypercalcemia||Some supplements are at the UL (e.g., "Carlson® Vitamin D3 — 4000 IU"). Unless one spend one's whole life in a basement, taking this as directed will put one over the UL.|
|Vitamin E||15 mg (M);
15 mg (F)
|Peripheral neuropathy, spinocerebellar ataxia, skeletal myopathy, pigmented & retinopathy, but "overt deficiency symptoms in normal individuals consuming diets low in vitamin E have never been described."||1000 mg||Hemorrhagic toxicity, inhibition of blood platelet effects||Scientology/Narconon's "Purification Rundown" includes of doses of up to 2400 IU of vitamin E. Depending on the form of vitamin E, this would be in the range of 1610-2690 µg.|
|Vitamin K||120 µg (M);
90 µg (F)
|Hypoprothrombinemia, increase in prothrombin time, bleeding||none established|
|Thiamin (B1)||1.2 mg (M);
1.1 mg (F)
|anorexia, weight loss, apathy, decrease in short-term memory, confusion, irritability, muscle weakness, cardiovascular effects such as an enlarged heart||none established|
|Riboflavin (B2)||1.3 mg (M);
1.1 mg (F)
|sore throat, hyperemia, edema of the pharyngeal & oral mucous membranes, cheilosis, angular stomatitis, glossitis (magenta tongue), seborrheic dermatitis, normochromic, anemia||none established|
|Niacin (B3)||16 mg (M);
14 mg (F)
|Pellagra, vomiting, constipation or diarrhea, bright red tongue, neurological symptoms||35 mg||Vasodilatory effects (flushing), gastrointestinal effects, hepatotoxicity, glucose intolerance, ocular effects||Scientology/Narconon's "Purification Rundown" includes of doses of niacin ranging from 100 mg up to 5000 mg.|
|B6||1.3-1.7 mg (M);
1.3-1.5 mg (F)
|Seborrheic dermatitis, microcytic anemia, epileptiform convulsions, depression, confusion||100 mg||Sensory neuropathy||Some supplements are at the UL (e.g., "Nature Made B-6 Vitamin 100 mg"). Unless one's diet is otherwise totally devoid of B6, taking this as directed will push one over the UL.|
|Folate (B9)||400 µg (M);
400 µg (F)
|Neural tube defects, other congenital anomalies, vascular disease; cancer, psychiatric and mental disorders||1000 µg||Neuropathy||Some supplements are at the UL (e.g., "PureFormulas Methyl Folate 1,000 mcg"). Unless one's diet is otherwise totally devoid of B9, taking this as directed will push one over the UL.|
|B12||2.4 µg (M);
2.4 µg (F)
|Pernicious anemia, neurological complications, gastrointestinal complaints||none established|
|Pantothenic acid (B5)||5 mg (M);
5 mg (F)
|Irritability & restlessness; fatigue; apathy; malaise; sleep disturbances; gastrointestinal complaints; neurobiological symptoms; hypoglycemia & increased sensitivity to insulin||none established|
|Biotin (B7)||30 µg (M);
30 µg (F)
|Dermatitis, conjunctivitis, alopecia, central nervous system abnormalities||none established|
|Choline||550 mg (M);
425 mg (F)
|Liver dysfunction||3500 mg||Body odor, sweating, and salivation; hypotension; hepatotoxicity|
|Arsenic||none established||no justification for supplementation due to toxicity|
|Boron||none established||20 mg/day (M);
20 mg/day (F)
|General systemic toxicity (implied by animal studies); dermatitis, alopecia, anorexia, indigestion (in humans)|
|Calcium||1000-1200 mg/day (M);1000-1200 mg/day (F)||Reduced bone mass, osteoporosis||2000-2500 mg/day (M);
2000-2500 mg/day (F)
|kidney stone formation, hypercalcemia, renal insufficiency|
|Chromium||30-35 µg/day (M);
20-25 µg/day (F)
|Weight loss, peripheral neuropathy, impairment of glucose utilization||none established|
|Copper||900 µg/day (M);
900 µg/day (F)
|Liver damage||10 mg/day (M);
10 mg/day (F)
|Gastrointestinal illness||Scientology/Narconon's "Purification Rundown" includes of doses of copper up to 12 mg|
|Fluoride||4 mg/day (M);
3 mg/day (F)
|Dental caries||10 mg/day (M);
10 mg/day (F)
|Enamel and skeletal fluorosis|
|Iodine||150 µg/day (M);
150 µg/day (F)
|Mental retardation, hypothyroidism, goiter, cretinism, other growth and developmental abnormalities||1100 µg/day (M);
1100 µg/day (F)
|Burning of the mouth, throat, and stomach, abdominal pain, fever, nausea, vomiting, diarrhea, weak pulse, cardiac irritability, coma, cyanosis, goiter, thyroid cancer|
|Iron||8 mg/day (M);
8-18 mg/day (F)
|Reduced physical work capacity, delayed psychomotor development in infants, impaired cognitive function, anemia||45 mg/day (M);
45 mg/day (M)
|Vomiting, diarrhea, constipation|
|Magnesium||400-420 mg/day (M);
310-320 mg/day (F)
|Hypocalcemia, neuromuscular hyperexcitability||350 mg/day (M);
350 mg/day (F)[note 3]
|Diarrhea, nausea, abdominal cramping|
|Manganese||2.3 mg/day (M);
1.8 mg/day (F)
|Impaired growth, impaired reproductive function, impaired glucose tolerance (based on animal studies)||11 mg/day (M);
11 mg/day (F)
|Neurotoxicity||Scientology/Narconon's "Purification Rundown" includes of doses of manganese up to 24 mg|
|Molybdenum||45 µg/day (M);
45 µg/day (F)
|Molybdenum deficiency has not been observed in healthy people.||2000 µg/day (M);
2000 µg/day (F)
|Reduced growth or weight loss, renal failure, skeletal abnormalities, infertility, anemia, diarrhea, and thyroid injury (based on animal studies)|
|Nickel||none established||1 mg/day (M);
1 mg/day (F)
|Reduced growth, weight loss, renal failure, skeletal abnormalities, infertility, anemia, diarrhea, and thyroid injury|
|Phosphorus||45 mg/day (M);
45 mg/day (F)
|Selenium||55 µg/day (M);
55 µg/day (F)
|Keshan disease, Kashin-Beck disease||400 µg/day (M);
400 µg/day (F)
|Silicon||none established||none established|
|Vanadium||none established||1.8 mg/day (M);
1.8 mg/day (F)
|"Although vanadium in food has not been shown to cause adverse effects in humans, there is no justification for adding vanadium to food, and vanadium supplements should be used with caution."|
|Zinc||11 mg/day (M);
8 mg/day (F)
|Diverse symptoms||40 mg/day (M);
40 mg/day (F)
|Epigastric pain, nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, headaches|
|Potassium||4700 mg/day (M);
4700 mg/day (F)
|Hypokalemia, high blood pressure, cardiovascular disease, bone demineralization, kidney stones||none established|
|Sodium||1300-1500 mg/day (M);
1200-1500 mg/day (F)
|Adverse effects on blood lipids, insulin resistance||2300 mg/day (M);
2300 mg/day (F)
|Increased blood pressure, cardiovascular disease|
|Chloride||1800-2300 mg/day (M);
1800-2300 mg/day (F)
|correlated with sodium||3600 mg/day (M);
3600 mg/day (F)
|correlated with sodium|
If you need to take a vitamin supplement it's worth remembering that there are degrees of how good a product is. So, always err on the side of caution. With that in mind, the following is a list of websites which monitor the quality of supplements (including vitamin supplements) and the claims of their makers.
- The American Journal of Clinical Nutrition: (http://www.ajcn.org)
- Consumer Lab: (https://www.consumerlab.com)
- Food and Drug Administration: (http://www.fda.gov/Food/DietarySupplements/)
- Institute of Food Technologies: (https://www.ift.org/)
- Medline Database: (https://www.nlm.nih.gov/medlineplus/)
- National Institutes of Health, Office of Dietary Supplements: (https://ods.od.nih.gov/)
- Supplement Watch: (http://www.supplementwatch.info/Vitamins/ListOfVitamins.html)
- Vox's supplement database (http://www.vox.com/a/supplements)
 See also
- Does Vitamin C Really Help Colds? by Lauren Cox (December 21, 2011 10:18am ET) Live Science.
- ↑ 1.0 1.1 When a range of values is given, it means that different DRIs are given for different adult age ranges
- ↑ 2.0 2.1 This is not necessarily an exhaustive list.
- ↑ Unlike the other values in the table, the UL for magnesium is for supplementation only, hence a comparable UL for magnesium would be the DRI plus the stated UL.
- ↑ Do vitamins in pills differ from those in food? by Christine Rosenbloom & Luke Bucci (2003) Scientific American.
- ↑ Nutritional Supplements Flexing Muscles As Growth Industry by David Lariviere (Apr 18, 2013 @ 07:09 PM) Forbes.
- ↑ More evidence that routine multivitamin use should be avoided by Scott Gavura (December 19, 2013) Science-Based Medicine.
- ↑ The Case Against Multivitamins Grows Stronger by Nancy Shute ( December 17, 201312:37 PM ET) NPR.
- ↑ WHO on Vitamin A deficiency
- ↑ Risk Factors for Lung Cancer and for Intervention Effects in CARET, the Beta-Carotene and Retinol Efficacy Trial by Gilbert S. Omenn et al. (1996). Journal of the National Cancer Institute 88(21):1550-1559.
- ↑ Serum Lycopene, Other Carotenoids, and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial by Ulrike Peters et al. (2007) Cancer Epidemiol. Biomarkers Prev. 16: 962-968 doi: 10.1158/1055-9965.EPI-06-0861
- ↑ Knowledge and Use of Folic Acid by Women of Childbearing Age — United States, 1995 MMWR Weekly September 29, 1995 / 44(38);716-8.
- ↑ Homocysteine and atherothrombosis by G.N. Welch & J. Loscalzo (1998) N. Engl. J. Med. 338:1042-1050.
- ↑ Nutritional Biochemistry by Tom Brody (1998). Academic Press, 2nd ed. ISBN 0121348369.
- ↑ Vitamin status and intake as primary determinants of homocysteinemia in an elderly population by J. Selhub et al. JAMA 1993;270:2693-2698
- ↑ 12.0 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 Nutrient Recommendations: Dietary Reference Intakes (DRI) National Institutes of Health Office of Dietary Supplements (2011).
- ↑ Vitamin B6, B12 and folic acid supplementation and cognitive function: a systematic review of randomized trials by E. M. Balk et al. Archives of Internal Medicine. 167(1):21-30, 2007 Jan 8.
- ↑ What Vitamins Should I Be Taking, Doctor? Willett WC, Stampfer MJ. N. Engl. J. Med. 345:1819, December 20, 2001.
- ↑ Thomas MK, Lloyd-Jones DM, Thadhani RI, et al. Hypovitaminosis D in medical inpatients. N. Engl. J. Med. 1998;338:777-783.
- ↑ Vitamin D, Race, and Excessive Daytime Sleepiness by David E. McCarty et al. (2012) Journal of Clinical Sleep Medicine 8(6):693-697.
- ↑ 'On Food and Cooking by Harold McGee (1997). Scribner. 1st ed. ISBN 0684843285. p. 539
- ↑ National Study Finds Vitamin E Supplement May Increase Prostate Cancer Risk (October 11, 2011) Cleveland Clinic.
- ↑ Joel D. Wallach, the "mineral doctor" The Skeptic's Dictionary
- ↑ Dead Doctors Don't Lie by Joel D. Wallach (2004) Wellness Publications, 2nd ed. ISBN 0974858102.
- ↑ Extra Vitamins? A Great Idea, Except in Denmark (Jun 16, 2011) New York Times.
- ↑ Orthomolecular therapy: its history and applicability to psychiatric disorders by F.J. Menolascino et al. (1988). Child Psychiatry Hum. Dev. 18 (3): 133–50. doi:10.1007/BF00709727.
- ↑ High-dose vitamin therapy stimulates variant enzymes with decreased coenzyme binding affinity (increased Km): relevance to genetic disease and polymorphisms1,2,3 by B. N. Ames et al. (2002). Am. J. Clin. Nutr. 75 (4): 616–58. PMID 11916749.
- ↑ For athletes, antioxidant pills may not help performance: Some supplements can blunt the positive effects of exercise training by Laura Beil (February 24, 2015) Science News.
- ↑ Dietary supplement use is associated with higher intakes of minerals from food sources by Regan L. Bailey et al. Am. J. Clin. Nutr. 2011 Nov; 94(5): 1376–1381. Published online 2011 Sep 28. doi: 10.3945/ajcn.111.020289.
- ↑ Vitamin A 10000 IU GNC
- ↑ 27.0 27.1 27.2 RFA Vitamin Conversion Chart Robert Forbes and Associates Regulatory Affairs
- ↑ 28.0 28.1 28.2 28.3 28.4 28.5 28.6 28.7 28.8 28.9 Is Narconon Safe? Dangerous detoxification by Chris Owen (5 November 2002) Narconon Exposed.
- ↑ 29.0 29.1 Overloading on Vitamin C? (March 16, 2009) Weil.
- ↑ The Third Face of Vitamin C by Robert F. Cathcart, Journal of Orthomolecular Medicine, 7:4;197-200, 1993.
- ↑ GNC Vitamin C 2000 MG — Crystals GNC
- ↑ Vitamin C Examine.com
- ↑ 33.0 33.1 33.2 Vitamin C for preventing and treating the common cold by Harri Hemilä & Elizabeth Chalker (2013). Cochrane Database of Systematic Reviews, Issue 1. Art. No.: CD000980. DOI:10.1002/14651858.CD000980.pub4.
- ↑ Carlson® Vitamin D3 — 4000 IU GNC (archived from February 27, 2017)
- ↑ The Rundown on Scientology's Purification Rundown: What Scientologists aren't telling you about their detox program (June 6,2007) New York Press (archived copy from July 12, 2009).
- ↑ Nature Made B-6 Vitamin 100 mg Target
- ↑ PureFormulas Methyl Folate 1,000 mcg PureFormulas
- ↑ Bob's Best Coral Calcium 2000 mg Robert Barefoot (archived from February 26, 2017)
- ↑ High Potency Slow Release Iron 45 mg Puritan's Pride (archived from February 27, 2017)
- ↑ Carlson® Magnesium 350 mg GNC (archived from February 27, 2017)
- ↑ Good State Liquid Ionic Selenium Minerals Supplement Amazon.com (archived from February 27, 2017)
- ↑ Acute Selenium Toxicity Associated With a Dietary Supplement by Jennifer K. MacFarquhar et al. Arch. Intern. Med. 2010 Feb 8; 170(3): 256–261. doi:10.1001/archinternmed.2009.495.
- ↑ Mason Natural Zinc, 100mg, Tablets Amazon.com (archived from February 27, 2017)