[Disease prevention by vitamins based on epidemiological investigations in humans]

Epidemiological studies in humans clearly indicate that higher consumption of vegetables and fruits, or a plant based diet, reduce the risk of cancer and coronary heart disease. Antioxidant vitamins or micro-nutrients contained in vegetables and fruits seem to be active components in the prevention of cancer and coronary heart disease. Intervention studies, however, failed to demonstrate protective effects. Further intervention studies with different study design are needed to clarify the role of supplemental vitamins or micro-nutrients in the prevention of cancer and coronary heart disease. The results of a few cohort and intervention studies have provided a good evidence that vitamin E supplement is protective against coronary heart disease.