Nutritional approach to cancer prevention with emphasis on vitamins, antioxidants, and carotenoids. The main human cancers are associated with complex life-style related causative, enhancing, and inhibiting factors. Tobacco smoking or chewing exposes humans to genotoxic carcinogens and to promoting substances. Likewise, Western dietary traditions involve certain carcinogens and promoters, whereas Oriental traditions implicate other carcinogens and promoters. Importantly, in virtually all situations regular intake of fruits and vegetables appreciably lowers the risk of cancer. This paper reviews the causes of the main human cancers and analyzes the mechanisms of the protective effects of fruits and vegetables. Prevention of human cancer requires the definition of optimal levels of recommended daily allowances of micronutrients. 