Study after study has found that vitamin and mineral supplements improve the immune function of elderly Americans. The specific nutrients with the most profound effects on immune function are EFAs, protein, zinc, vitamin A, vitamin B6, folic acid and iron. Among the healthy elderly, immune boosting benefits have been demonstrated for anti-oxidants like zinc, selenium, vitamin E and beta-carotene.
Protection against the effects of environmental pollution, free-radical induced cell damage and cancer is provided by dietary anti-oxidants. Foods that are richest in these anti-oxidants are red, yellow and green vegetables, uncooked nuts and seeds (like almonds and sunflower seeds), and fish.
The appetizing colors of fresh fruits and vegetables derive from the presence of special groups of anti-oxidants. Carotenoids are fat-soluble compounds which range in hue from light yellow to deep orange. The flagship carotenoid is beta-carotene, the orange pigment evident in carrots and cantaloupe. In the body, beta-carotene is converted to vitamin A, but the importance of carotenoids for human health extends far beyond beta-carotene's role as a precursor of vitamin A. Dietary supplements of beta-carotene are ineffective in preventing cancer or heart disease, whereas food that is high in beta-carotene and other carotenoids does confer protection. Scientists have previously paid insufficient attention to these other carotenoids, like alpha-carotene, lutein, lycopene and the xanthins. They do not serve as pre-cursors of vitamin A, yet their consumption may be as effective as consumption of beta-carotene in decreasing the risk of cancer, probably because they exert significant anti-oxidant effects of their own. I do not recommend nutritional supplements containing beta-carotene to my patients. Instead, I recommend a diet high in mixed carotenoids, which includes many different varieties of fruits and vegetables: carrots, broccoli, spinach, tomatoes, winter squash and papaya. Sea vegetables like kelp, wakame, dulse, hiziki and nori are especially rich in mixed carotenoids. They can be quite tasty cooked or raw, along with rice or beans or in salad.
The darker colors of fruits and vegetables are supplied by a group of compounds called bioflavonoids, which typically range from bright yellow to deep purple in hue. There are over four hundred bioflavonoids in the human diet. They are widely distributed in fruits, vegetables, beverages and spices. A typical North American consumes about one gram of bioflavonoids per day; Asians may consume over five grams per day, much of it coming from herbs and spices. Bioflavonoids are potent anti-oxidants that not only contribute to the health benefits of fruits and vegetables but also to the therapeutic effects of many traditional Chinese and Indian herbal remedies. The bioflavonoids which give grapes their purple color are believed responsible for the protection against heart disease which is offered by red wine. Epigallocatechin gallate (EGCG), the bioflavonoid which is the main constituent of green tea, is credited with the protection against cancer that results from drinking green tea.
A number of foods stimulate the body to produce more of the enzymes used for detoxicating the body from cancer-causing chemicals. These foods have been shown to improve liver detoxification and to decrease the risk of developing cancer. They include members of the cabbage family (crucifers), which includes not only cabbage but broccoli, cauliflower, bok choy and brussel sprouts, and also green onions and kale. These vegetables contain compounds called aryl isothiocyanates which directly stimulate the activity of an enzyme, glutathione S-transferase, an important component of the Phase Two system. Activation of liver detoxification probably explains the highly publicized effects of broccoli, brussel sprouts and cabbage in preventing cancer in humans and experimental animals.