What are Antioxidants?
Antioxidants are a diverse group of chemicals that can be naturally found in vegetables, fruits and plants in general. Antioxidants are also synthesized in our body.
Examples of dietary antioxidants are vitamin E, C, A, phenolic acids, selenium, chlorophyll and cholorphyll derivatives, carotenoids, flavonoids, glutathione, coenzyme Q 10, melatonin, and lycopene. Synthetic dietary antioxidants include butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT).
Chemicals produced in human body that have antioxidant capacity are uric acid, high density lipo-protein (HDL), and amino acids such as arginine.
Health Benefits of Antioxidants
Antioxidants are suggested to have anti-aging effect because they are scavengers of free radicals (and other reactive oxygen species). Free radicals are associated with human diseases including cancer, cardiovascular disease, and with aging. They are also associated with other aging-related diseases such as Alzheimer’s disease and Parkinson’s disease.
Antioxidants protect the body from oxidative damage induced by free radicals and reactive oxygen species by (1) suppressing their formation; (2) acting as scavengers; and (3) acting as their substrate.
Antioxidant and Immune System
Antioixdants are essential for proper function of the immune system. This is partly because immune cells produce free-radicals for normal defense functions. If the level of free radicals in the immune cells surpasses beyond the normal level, they negatively affect the immune system. On the other hand, antioxidants act as scavengers of the free radicals in cells and there fore promote our immunity. Imbalance between free radical and antioxidants in cells, due to deficiency in single or multiple antioxidants has been reported to result in weakness of immunity function.
Antioxidants boost immunity system also by playing other important roles such as in cellular metabolism, signal transduction, gene activation, and transcription. High density lipo-protein (HDL) cholesterol has inhibitory effect against oxidation of low density lipo-protein, which is implicated with development of atherosclerosis and cardiovascular diseases. High density lipo-protein (HDL) also prevents endothelial cell dysfunction and activation, maintain the integrity of the endothelial cell lining, and reduce the deleterious effect of oxidized low density lipo-protein (LDL) cholesterol and the levels of thrombogenic factors.
Antioxidant Diet
There is no such a definite antioxidant diet or formula. What is known is that a diet rich in fruits, vegetables, and whole grain foods provides high amount and a variety of antioxidants.
An example of high fiber foods and high in antioxidants is traditional Mediterranean diet. It is rich in vegetables, fruits, legumes, and whole grain foods. Multiple studies have been conducted on Mediterranean populations, their diet and mortality due to diseases that are associated with free radicals. There is strong evidence that indicates Mediterranean diet is associated with the lower mortality caused by cardiovascular disease and cancer in the Mediterranean populations. And, its health benefit is explained partly by its high content of antioxidants.
Natural Food Sources High in Antioxidant
A variety of fruits, vegetables, nuts, whole grain cereals and legumes, tea, red wine, and herbs (eg. rosemary extract) are rich sources of natural antioxidants. The benefit of eating whole fruits, vegetables, and whole grain foods, in contrast to antioxidant supplements, is that they contain a variety of natural antioxidants. A combination of multiple antioxidants has greater health benefit than when an antioxidant is taken individually. Furthermore, the antioxidant content tends to be high on their outer layer of the plant products. For example, in cereals, the bran is richer in antioxidants such as phenolic acids, and phytic acid than the inner part of the grain. A study comparing high bran, whole grain cereals and refined wheat cereals documented that the high bran and whole grain cereals contained higher antioxidants content than the refined wheat cereal.
Food high in antioxidants include fruits such as apple, grape, grapefruit, crane berry, black berry and blueberry. Even though, comprehensive studies on antioxidant content of foods are yet to come, among the best antioxidant sources are crane berry, black berry and blue berry. Vegetables are also rich antioxidant sources. Red bean, pinto bean, kidney bean, carrot, tomato, garlic and Russet potato are among the vegetables high in antioxidant content and categorized among the best antioxidant sources. Other important sources of antioxidants are green tea, black tea, herbal tea, spices, red wine, ginger, and garlic.
References:
Salvayre, A.N, Nicole Dousset, Gianna Ferretti, Tiziana Bacchetti, Giovanna Curatola and Robert Salvayre. 2006. Antioxidant and cytoprotective properties of high-density lipoproteins in vascular cells Free Radical Biology and Medicine, Vol. 41(7): 1031-1040.
Papas, A. 1999. Diet and Antioxidants Status: In Antioxidant Status, Diet, Nutrition and Health. ed. Andreas M. Papas. pp. 89-106. CRC Press, New York.
Wu, D. and Simin N. Meydini. 1999. Antioxidants and Immune Function: In Antioxidant Status, Diet, Nutrition and Health. ed. Andreas M. Papas. pp. 371 - 400. CRC Press, New York.