In general, the vitamin megadoses advocated by orthomolecular medicine are unsupported by scientific consensus.[31] Some vitamins are toxic in high doses,[64] including niacin (B3),[65] cholecalciferol (D)[66] and tocopherol (E).[67] Evidence does not support the efficacy of orthomolecular medicine in treating cancer or psychological health[68][69] and its claims have been criticized by most medical organizations, including the American Cancer Society, the American Psychiatric Association, the National Institute of Mental Health,[50] the American Academy of Pediatrics,[70] CHAMPUS, and the Canadian Paediatric Society. The American Medical Association describes as "myths" the ideas that adequate nutrition is not readily achievable with normal food, all food grown with pesticide is poisonous, all food additives are poisonous, vitamin and mineral deficiencies are common, that the cause of most disease is poor diet, which can be prevented by nutritional supplements. [71]
Similarly, the American Cancer Society comments that the current scientific evidence does not "support use of orthomolecular therapy for most of the conditions for which it is promoted." Some supplements have exhibited benefits for specific conditions, while a few have been confirmed to be harmful; the consumption of nutritious foods is the best recognized method to obtain vitamins, minerals, and nutrients crucial for good health.[31] Barrie Cassileth, an adviser on alternative medicine to the National Institutes of Health, stated that "scientific research has found no benefit from orthomolecular therapy for any disease,"[52] and medical textbooks also report that there is "no evidence that megavitamin or orthomolecular therapy is effective in treating any disease."[72]
A 1973 task force of the American Psychiatric Association unanimously concluded:
This review and critique has carefully examined the literature produced by megavitamin proponents and by those who have attempted to replicate their basic and clinical work. It concludes in this regard that the credibility of the megavitamin proponents is low. Their credibility is further diminished by a consistent refusal over the past decade to perform controlled experiments and to report their new results in a scientifically acceptable fashion. Under these circumstances this Task Force considers the massive publicity which they promulgate via radio, the lay press and popular books, using catch phrases which are really misnomers like "megavitamin therapy" and "orthomolecular treatment," to be deplorable.[73]
In response to claims that orthomolecular medicine could cure childhood psychoses and learning disorders, the American Academy of Pediatrics labelled orthomolecular medicine a "cult" in 1976.[74]
Proponents of orthomolecular medicine counter that some vitamins and nutrients are now used in medicine as treatments for specific diseases, such as megadose niacin and fish oil for dyslipidemias, and megavitamin therapies for a group of rare inborn errors of metabolism.[20] A review in the Annals of Internal Medicine concluded that while some therapies might be beneficial, others might be harmful or interfere with effective medical therapy.[75] A recent study of over 161,000 individuals 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."[76] A recent meta-analysis in JAMA suggested that supplementation with combinations of antioxidant vitamins (beta-carotene, vitamin A, and vitamin E) may increase mortality, although with respect to beta-carotene this conclusion may be due to the known harmful effect in smokers.[77]
