Antioxidants remove potentially damaging oxidizing agents – known as free radicals – from within the body. Free radicals can damage DNA, as well as proteins and lipids within cells, altering or inhibiting cellular function. They may be generated by strenuous physical activity; physiological processes, especially in defense against microbes and other foreign substances; and especially exposure to harmful environmental factors, such as smog, ozone, chemicals, drugs, smoking and radiation. Dietary antioxidants – which include carotenoids and vitamins E and C – help control or eliminate free radicals by donating electrons to cells throughout the body. This offsets the potential damage caused by free radicals and helps maintain cellular health.
Exogenous antioxidants are available through the diet and include amino acids (N-acetyl-L-cysteine, taurine and L-glutathione), carotenoids (beta-carotene, lycopene, lutein and zeaxanthin), minerals (selenium and zinc) and vitamins C and E. Endogenous antioxidants are produced in the body and include ubiquinone/ubiquinol (CoQ10), alpha lipoic acid, and superoxide dismutase (SOD), the master cellular defense enzyme. However, supplementation of endogenous antioxidants is essential since many factors – the normal aging process, medications and oxidative stress – have been found to compromise their levels in the body.
Carotenoids (or carotenes) are colorful, fat-soluble compounds that occur naturally in many fruits, grains, oils and vegetables – such as apricots, whole grains, palm oil, carrots, sweet potatoes, squash, and spinach. Plants produce carotenoids to attract insects for pollination and animals for seed distribution. These compounds also act as a natural sunscreen, protecting plants from ultraviolet light.
Alpha, beta, and gamma carotene, the most popular carotenoids, are known as provitamins because they can be converted to active vitamin A.
Astaxanthin is a pigment responsible for the pink-to-red colors found in crustaceans, salmonoids and other fish, as well as algae. The antioxidant properties of astaxanthin are more potent than those of ascorbic acid (vitamin C), beta-carotene and d-alpha tocopherol (vitamin E). Astaxanthin is particularly useful in skin and eye health due to its powerful ability to absorb ultraviolet, especially UVB, rays.
Lycopene, the hydrocarbon carotenoid that gives tomatoes their red color, is one of the most potent antioxidants. Clinical studies have shown that lycopene not only supports prostate health, but also helps maintain heart, eye and skin health.
Lutein and zeaxanthin provide the yellow-to-orange pigments found in corn and leafy greens, such as kale and spinach. Both are believed to function as protective antioxidants in the macular region of the human retina. Lutein also plays a key role in maintaining skin and cardiovascular health.
Polyphenols represent a category of more than 8,000 different plant compounds that include simple phenolics, as well as highly polymerized compounds, such as tannins. Bioflavonoids or flavonoids are the best-known polyphenols. Most are derived from citrus fruits and work synergistically with vitamin C and other antioxidants to provide extra protection to the immune system. They also support healthy circulation by helping maintain the walls of small blood vessels. Resveratrol, a bioflavonoid found in more than 70 different plant species including red wine grapes and Japanese knotweed, is known for its heart healthy benefits. Proanthocyanidins and anthocyanidins – bioflavonoids commonly found in red wine and grape seed extracts, as well as in fruits and vegetables commonly found in the Mediterranean diet – have long been known for their capillary and cardio-protective effects. Other common bioflavonoid subclasses are flavones (for example, apigenin and luteolin), flavonols (quercetin, kaempferol and myricetin), isoflavones (genistein, daidzein and glycitein), flavanols (gallic acids, catechins, EGCG and GC), flavanones (naringenin), and glycosides (rutin).