Vitamins: physiology and deficiency states.

Approximately half of the people in the United States take vitamin supplements, and some use alarmingly high doses. In this article, physiological functions of vitamins and the effects of vitamin deficiencies are summarized. Common food sources of vitamins are listed and a suggested daily eating guide is provided to assist in proper food intake. Adding vitamin supplements to a poor diet may alleviate some symptoms of deficiency, but cannot compensate for the lack of other nutrients. For optimum health, balanced, wholesome meals are recommended.