New perspectives on function of vitamins.

Newer aspects of vitamin function are reviewed from a biochemical perspective. Specifically, six themes are developed that include 1) mechanisms and biochemical functions important to oxidant defense, 2) new functions associated with the actions of vitamin D, 3) vitamin K and calcium homeostasis, 4) folic acid and the methylation of DNA, 5) beta-carotene and cellular communication, and 6) newly identified roles for vitamin B6. A decade ago, it was considered highly speculative to propose approaches to disease prevention that involved vitamin supplementation. Nutrition paradigms important to vitamin function, however, have now shifted to include more focus on disease prevention and consideration of supplements. Considerable work has also evolved to provide basic biochemical and physiological mechanisms as bases for the interaction between vitamin status and health.