Claims | Health effects from very high doses of vitamins. |
---|---|
Related scientific disciplines | vitamins, dietary supplements |
Year proposed | 1930s |
Notable proponents | Frederick Klenner, Linus Pauling |
(Overview of pseudoscientific concepts) |
This article is part of a series on |
Alternative medicine |
---|
Megavitamin therapy is the use of large doses of vitamins, often many times greater than the recommended dietary allowance (RDA) in the attempt to prevent or treat diseases. Megavitamin therapy is typically used in alternative medicine by practitioners who call their approach orthomolecular medicine. [1] Vitamins are useful in preventing and treating illnesses specifically associated with dietary vitamin shortfalls, but the conclusions of medical research are that the broad claims of disease treatment by advocates of megavitamin therapy are unsubstantiated by the available evidence. [2] [3] It is generally accepted that doses of any vitamin greatly in excess of nutritional requirements will result either in toxicity (vitamins A and D) or in the excess simply being metabolised; thus evidence in favour of vitamin supplementation supports only doses in the normal range. [4] [5] [6] Critics have described some aspects of orthomolecular medicine as food faddism or even quackery. [7] [8] [9] Research on nutrient supplementation in general suggests that some nutritional supplements might be beneficial, and that others might be harmful; [10] [11] [12] several specific nutritional therapies are associated with an increased likelihood of the condition they are meant to prevent. [13]
Megavitamin therapy must be distinguished from the usual "vitamin supplementation" approach of traditional multivitamin pills. Megavitamin doses are far higher than the levels of vitamins ordinarily available through western diets. A study of 161,000 individuals (post-menopausal women) provided, in the words of the authors, "convincing evidence that multivitamin use has little or no influence on the risk of common cancers, cardiovascular disease, or total mortality in postmenopausal women". [14]
In the 1930s and 1940s, some scientific and clinical evidence suggested that there might be beneficial uses of vitamins C, E, and niacin in large doses. Beginning in the 1930s in Canada, a megadose vitamin E therapy for cardiovascular and circulatory complaints was developed by Evan Shute and colleagues, named the "Shute protocol". [15] Tentative experiments in the 1930s by Claus W. Jungeblut [16] with larger doses of vitamin C led to Frederick Klenner's development of megadose intravenous vitamin C treatments for polio and other viruses in the 1940s. [17] William Kaufman published articles in the 1940s that detailed his treatment of arthritis with frequent, high doses of niacinamide. [18] Rudolf Altschul and Abram Hoffer applied large doses of the immediate release form of niacin (Vitamin B3) to treat hypercholesterolemia. [19] [20] In a 1956 publication entitled Biochemical Individuality, Roger J. Williams introduced concepts for individualized megavitamins and nutrients. [21] Megavitamin therapies were also publicly advocated by Linus Pauling in the late 1960s. [22]
Although megavitamin therapies still largely remain outside of the structure of evidence-based medicine, they are increasingly used by patients, with or without the approval of their treating physicians, often after recommendations by practitioners of orthomolecular and naturopathic medicine. [23] The proposed efficacy of various megavitamin therapies to reduce cancer risk has been contradicted by results of one clinical trial. [24]
The US Recommended Dietary Allowance for vitamin C for adult women is 76 mg/day and for adult men 90 mg/day. Although Linus Pauling was known for highly respectable research in chemistry and biochemistry, he was also known for promoting the consumption of vitamin C in large doses. [25] Although he claimed and stood firm in his claim that consuming over 1,000 mg is helpful for one’s immune system when fighting a head cold, the results of empirical research do not align with this view. A meta-analysis concluded that supplementary vitamin C significantly lowered serum uric acid, considered a risk factor for gout. [26] One population study reported an inverse correlation between dietary vitamin C and risk of gout. [27] A review of clinical trials in the treatment of colds with small and large doses of Vitamin C has established that there is no evidence that it decreases the incidence of common colds. [28] After 33 years of research, it is still not established whether vitamin C can be used as a treatment for cancer. [29]
The US Recommended Dietary Allowance for vitamin E for adult women and men is 15 mg/day. The US Food and Nutrition Board set a tolerable upper intake level (UL) at 1,000 mg (1,500 IU) per day derived from animal models that demonstrated bleeding at high doses. [30] In the US, the popularity for vitamin E as a dietary supplement peaked around 2000, with popular doses of 400, 800 and 1000 IU/day. Declines in usage were attributed to publications of meta-analyses that showed either no benefits or negative consequences from vitamin E supplements. [31] [32] [33] [34] [35] [36]
The US Recommended Dietary Allowance for niacin for adult women is 14 mg/day and for adult men 16 mg/day. Niacin is available as a prescription product, either immediate release (500 mg tablets; prescribed up to 3,000 mg/day) or extended release (500 and 1,000 mg tablets; prescribed up to 2,000 mg/day). In the US, niacin is also available as a dietary supplement at 500 to 1,000 mg/tablet. Niacin has sometimes been used in combination with other lipid-lowering medications. [37] Systematic reviews found no effect of niacin on cardiovascular disease or death, in spite of raising high-density lipoprotein (HDL) cholesterol. Reported side effects include an increased risk of diabetes. [38] [39] [40]
Related topics
Vitamin topics
Vitamin C is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription dietary supplement. As a therapy, it is used to prevent and treat scurvy, a disease caused by vitamin C deficiency.
Vitamins are organic molecules that are essential to an organism in small quantities for proper metabolic function. Essential nutrients cannot be synthesized in the organism in sufficient quantities for survival, and therefore must be obtained through the diet. For example, vitamin C can be synthesized by some species but not by others; it is not considered a vitamin in the first instance but is in the second. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, there are eight vitamers of vitamin E: four tocopherols and four tocotrienols.
Niacin, also known as nicotinic acid, is an organic compound and a vitamer of vitamin B3, an essential human nutrient. It is produced by plants and animals from the amino acid tryptophan. Niacin is obtained in the diet from a variety of whole and processed foods, with highest contents in fortified packaged foods, meat, poultry, red fish such as tuna and salmon, lesser amounts in nuts, legumes and seeds. Niacin as a dietary supplement is used to treat pellagra, a disease caused by niacin deficiency. Signs and symptoms of pellagra include skin and mouth lesions, anemia, headaches, and tiredness. Many countries mandate its addition to wheat flour or other food grains, thereby reducing the risk of pellagra.
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E functions as a fat-soluble antioxidant which may help protect cell membranes from reactive oxygen species. Various government organizations recommend that adults consume between 3 and 15 mg per day, whereas a worldwide review reported a median dietary intake of 6.2 mg per day. Foods rich in vitamin E include seeds, nuts, seed oils, peanut butter, and vitamin E-fortified foods. Symptomatic vitamin E deficiency is rare, is usually caused by an underlying problem with digesting dietary fat rather than from a diet low in vitamin E. Deficiency can cause neurological disorders.
Tocopherols are a class of organic compounds comprising various methylated phenols, many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, it was named tocopherol, from Greek τόκοςtókos 'birth' and φέρεινphérein 'to bear or carry', that is 'to carry a pregnancy', with the ending -ol signifying its status as a chemical alcohol.
Vitamin B6 is one of the B vitamins, and thus an essential nutrient. The term refers to a group of six chemically similar compounds, i.e., "vitamers", which can be interconverted in biological systems. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in more than 140 enzyme reactions in amino acid, glucose, and lipid metabolism.
Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage. Folate is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division and maturation of blood cells. As the human body cannot make folate, it is required in the diet, making it an essential nutrient. It occurs naturally in many foods. The recommended adult daily intake of folate in the U.S. is 400 micrograms from foods or dietary supplements.
A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources, or that are synthetic. The classes of nutrient compounds in supplements include vitamins, minerals, fiber, fatty acids, and amino acids. Dietary supplements can also contain substances that have not been confirmed as being essential to life, and so are not nutrients per se, but are marketed as having a beneficial biological effect, such as plant pigments or polyphenols. Animals can also be a source of supplement ingredients, such as collagen from chickens or fish for example. These are also sold individually and in combination, and may be combined with nutrient ingredients. The European Commission has also established harmonized rules to help insure that food supplements are safe and appropriately labeled.
Orthomolecular medicine is a form of alternative medicine that claims to maintain human health through nutritional supplementation. It is rejected by evidence-based medicine. The concept builds on the idea of an optimal nutritional environment in the body and suggests that diseases reflect deficiencies in this environment. Treatment for disease, according to this view, involves attempts to correct "imbalances or deficiencies based on individual biochemistry" by use of substances such as vitamins, minerals, amino acids, trace elements and fatty acids. The notions behind orthomolecular medicine are not supported by sound medical evidence, and the therapy is not effective for chronic disease prevention; even the validity of calling the orthomolecular approach a form of medicine has been questioned since the 1970s.
Cholecalciferol, also known as vitamin D3 or colecalciferol, is a type of vitamin D that is produced by the skin when exposed to UVB light; it is found in certain foods and can be taken as a dietary supplement.
Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases, heart failure, hypertensive heart disease, rheumatic heart disease, cardiomyopathy, arrhythmia, congenital heart disease, valvular heart disease, carditis, aortic aneurysms, peripheral artery disease, thromboembolic disease, and venous thrombosis.
β-Carotene (beta-carotene) is an organic, strongly colored red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons.
A multivitamin is a preparation intended to serve as a dietary supplement with vitamins, dietary minerals, and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids, or injectable formulations. Other than injectable formulations, which are only available and administered under medical supervision, multivitamins are recognized by the Codex Alimentarius Commission as a category of food.
Fish oil is oil derived from the tissues of oily fish. Fish oils contain the omega−3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), precursors of certain eicosanoids that are known to reduce inflammation in the body and improve hypertriglyceridemia. There has been a great deal of controversy in the 21st century about the role of fish oil in cardiovascular disease, with recent meta-analyses reaching different conclusions about its potential impact.
The Women's Health Initiative (WHI) was a series of clinical studies initiated by the U.S. National Institutes of Health (NIH) in 1991, to address major health issues causing morbidity and mortality in postmenopausal women. It consisted of three clinical trials (CT) and an observational study (OS). In particular, randomized controlled trials were designed and funded that addressed cardiovascular disease, cancer, and osteoporosis.
Orthomolecular psychiatry is the use of orthomolecular medicine for mental illness. Orthomolecular psychiatry has been rejected by evidence-based medicine and has been called quackery. The approach uses unorthodox forms of individualized testing and diagnosis to attempt to establish an etiology for each patient's specific symptoms, and claims to tailor the treatment accordingly, using a combination of nutrients, dietary changes and medications that are claimed to enhance quality of life and functionality as well as to reduce or eliminate symptoms and the use of xenobiotic drugs. Scientific studies have shown mixed results; although there are some promising results from nutritional psychiatry, some forms of orthomolecular psychiatry are ineffective.
Abram Hoffer was a Canadian biochemist, physician, and psychiatrist known for his "adrenochrome hypothesis" of schizoaffective disorders. According to Hoffer, megavitamin therapy and other nutritional interventions are potentially effective treatments for cancer and schizophrenia. Hoffer was also involved in studies of LSD as an experimental therapy for alcoholism and the discovery that high-dose niacin can be used to treat high cholesterol and other dyslipidemias. Hoffer's ideas about megavitamin therapy to treat mental illness are not accepted by the medical community.
Vitamin C megadosage is a term describing the consumption or injection of vitamin C in doses well beyond the current United States Recommended Dietary Allowance of 90 milligrams per day, and often well beyond the tolerable upper intake level of 2,000 milligrams per day. There is no strong scientific evidence that vitamin C megadosage helps to cure or prevent cancer, the common cold, or some other medical conditions.
Vitamin D deficiency or hypovitaminosis D is a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate exposure to sunlight, particularly sunlight with adequate ultraviolet B rays (UVB). Vitamin D deficiency can also be caused by inadequate nutritional intake of vitamin D; disorders that limit vitamin D absorption; and disorders that impair the conversion of vitamin D to active metabolites, including certain liver, kidney, and hereditary disorders. Deficiency impairs bone mineralization, leading to bone-softening diseases, such as rickets in children. It can also worsen osteomalacia and osteoporosis in adults, increasing the risk of bone fractures. Muscle weakness is also a common symptom of vitamin D deficiency, further increasing the risk of fall and bone fractures in adults. Vitamin D deficiency is associated with the development of schizophrenia.
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, along with numerous other biological functions. In humans, the most significant compounds within this group are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol).