Vitamins in health and aging.

The use of various dietary supplements, including vitamins, to prevent or delay disease or aging rests for the most part on epidemiological associations. It does appear from these data that a diet rich in vitamins is associated with a tendency to improved health; however, the results from controlled trials are dismal. The discrepancy between different types of studies is probably explained by the fact that dietary composition and supplement use is a component in a cluster of healthy behaviors. An alternative hypothesis is that there are as-yet-unknown essential organic compounds in certain foods. The most prudent approach is to recommend a daily intake of fruits and vegetables as a likely source of essential nutrients. Failing compliance with a natural source of essential nutrients, and in populations at high risk of vitamin deficiency, vitamin supplements should be encouraged.