Phytochemicals are protective, disease preventing non-nutritive compounds of plant origin. Studies have shown that these chemicals have various biological effects on the body. Many of them act as antioxidants (delays the process of ageing), some improve functioning of the immune system, and others alter enzymes that metabolize drugs in our system.
However, further studies are still required to assess the efficacy or action of these foods in disease prevention. Until further research uncovers the adequate quantity, American Heart Association (AHA) recommends that eating a balanced meal consisting of a variety of fruits, vegetables and whole grain product ensure optimum intake of Phytochemicals.
Clinical trials have indicated that the beneficial effect of these phytochemicals can be obtained only when they are consumed in the form of a balanced meal and such effects are not demonstrated when individual nutrients are consumed in the form of supplements. Hence, the benefits of phytochemicals can be best achieved by consuming a varied diet that includes a minimum of five servings of fruits and vegetables, rather than in supplement form.
Some rich sources of phytochemicals include tomatoes, citrus fruits, kiwi fruit, spinach, grapes, grapefruit, berries, mango, sweet pepper, cauliflower, broccoli, cabbage, carrot, peas, garlic, onion, soyabean, lentils, beans, buckwheat, nuts, and other whole grains.