JAMA 2002 (Jun 19); 287 (23): 3127–3129
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Robert H. Fletcher, MD, MSc; Kathleen M. Fairfield, MD, DrPH
Vitamin deficiency syndromes such as scurvy and beriberi are uncommon in Western societies. However, suboptimal intake of some vitamins, above levels causing classic vitamin deficiency, is a risk factor for chronic diseases and common in the general population, especially the elderly. Suboptimal folic acid levels, along with suboptimal levels of vitamins B6 and B12, are a risk factor for cardiovascular disease, neural tube defects, and colon and breast cancer; low levels of vitamin D contribute to osteopenia and fractures; and low levels of the antioxidant vitamins (vitamins A, E, and C) may increase risk for several chronic diseases. Most people do not consume an optimal amount of all vitamins by diet alone. Pending strong evidence of effectiveness from randomized trials, it appears prudent for all adults to take vitamin supplements. The evidence base for tailoring the contents of multivitamins to specific characteristics of patients such as age, sex, and physical activity and for testing vitamin levels to guide specific supplementation practices is limited. Physicians should make specific efforts to learn about their patients' use of vitamins to ensure that they are taking vitamins they should, such as folate supplementation for women in the childbearing years, and avoiding dangerous practices such as high doses of vitamin A during pregnancy or massive doses of fat-soluble vitamins at any age.
From the FULL TEXT Article:
Vitamins are organic compounds that cannot be synthesized by humans and therefore must be ingested to prevent metabolic disorders. Although classic vitamin deficiency syndromes such as scurvy, beriberi, and pellagra are now uncommon in Western societies, specific clinical subgroups remain at risk (Table 1). For example, elderly patients are particularly at risk for vitamins B12 and D deficiency, alcohol-dependent individuals are at risk for folate, B6, B12, and thiamin deficiency, and hospitalized patients are at risk for deficiencies of folate and other water-soluble vitamins. Inadequate intake or subtle deficiencies in several vitamins are risk factors for chronic diseases such as cardiovascular disease, cancer, and osteoporosis. In addition, pregnancy or alcohol use may increase vitamin requirements. At least 30% of US residents use vitamin supplements regularly, suggesting that physicians need to be informed about available preparations and prepared to counsel patients in this regard.  At a minimum, patients should be queried about their usual diet and use of vitamin supplements.
We searched MEDLINE for English-language articles published from 1966 through January 11, 2002, about vitamins, vitamin deficiencies and toxicity, and specific vitamins in relation to chronic diseases. We paid specific attention to cardiovascular disease, common cancers (lung, colon, breast, and prostate), neural tube defect, and osteoporosis. We reviewed reference lists from retrieved articles for additional pertinent information. The coauthors reviewed the references jointly and attempted to synthesize the material, placing emphasis on randomized trial data where available. Table 2 summarizes the cohort and randomized trial data for the most important vitamin-disease relationships. We reviewed the 9 vitamins that are especially central in the preventive care of adults: folate, vitamins B6 and B12, vitamin D, vitamin E, the provitamin A carotenoids, vitamin A, vitamin C, and vitamin K. We did not include thiamin (vitamin B1) or riboflavin (B2), because of little evidence of their relationship to chronic disease. We include the carotenoid lycopene, although it does not have provitamin A activity and is therefore not a true vitamin. Similarly, vitamin D is not a true vitamin because it can be synthesized by humans, but for the sake of simplicity we use the term vitamin to refer to these compounds.
Current recommendations are expressed as daily values, a new dietary reference term that is made up of reference daily intakes (RDIs) for vitamins and minerals, which has replaced US recommended daily allowance, and daily reference values for fats, protein, fiber, sodium, and potassium. Table 3 summarizes the RDIs for vitamins.
Although the clinical syndromes of vitamin deficiencies are unusual in Western societies, suboptimal vitamin status is not. Because suboptimal vitamin status is associated with many chronic diseases, including cardiovascular disease, cancer, and osteoporosis, it is important for physicians to identify patients with poor nutrition or other reasons for increased vitamin needs. The science of vitamin supplementation for chronic disease prevention is not well developed, and much of the evidence comes from observational studies.