Nutritional interventions in cancer prevention.

The first generation of phase III nutritional intervention studies to prevent cancer has been completed. Nearly 150,000 total participants were studied in nine different interventions using randomized, double-blind, placebo-controlled designs that tested whether vitamins and/or minerals, given singly or in combination, could prevent total or site-specific cancer. The primary agents tested include beta-carotene, alpha-tocopherol, selenium, and retinol. This review summarizes the findings from the first generation of human experimental studies that tested micronutrients in the prevention of cancer, discusses lessons learned from these studies, identifies the most promising leads, and describes future prospects in nutritional intervention research.