The role of vegetables and fruits is now well established in preventing all types of cancer; beta-carotene and vitamin C are considered supporting players. However, use of whole fruits and vegetables rather than their extracts or pills derived from them work better because there are yet unknown cancer preventing mechanisms which can not be provided in the isolated components. Relative merit of different types of fruits and vegetables in preventive disease is not yet established. Our best bet is to select them on the basis of total calories; lesser the better.

Dietary fiber lowers blood pressure and reduces risk of CHD. Vitamins B-6 and folic acid are now known to reduce risk of CHD by a unique mechanism of lowering a specific factor, homocysteine, in the blood.

Vegetarians and non-vegetarians who consume large quantities of vegetables and fruits have generally lower blood pressure. Dietary antioxidants, carotenoids and vitamin C, reduce the risk of cataracts by reducing accumulation of oxidized and denatured proteins in the lens.