By Will Block
Like rust damaging a car, oxidation can damage our cells, causing disease and accelerating the aging process. Medical research has shown, however, that antioxidants can help our cells defend themselves against such damage. Antioxidants come in different forms: some are familiar vitamins or minerals, but most are nonvitamin phytochemicals—organic compounds found in plants, including foods.
Antioxidants protect our cells by neutralizing free radicals, the highly reactive molecules produced when cellular energy is generated by the reaction of oxygen and glucose. (Other sources of free radicals are compounds that come from smoking, eating fatty foods—especially fried foods—and breathing polluted air.) Free radicals attack the principal components of our cells—lipids, proteins, and nucleic acids—causing cumulative long-term damage.
The Antioxidant Network
Five antioxidants—lipoic acid, vitamin C, vitamin E, coenzyme Q10, and glutathione—are particularly important because they form a unique antioxidant network: they interact with one another so as to regenerate their antioxidant capacities after they have successfully neutralized free radicals. Thus, our bodies can use these molecules again and again (with some inevitable attrition along the way) rather than just once, as with most other antioxidants.
Because lipoic acid is the linchpin of the antioxidant network—it alone can regenerate the other four (and the only one that can do this to itself)—it has been called “the antioxidant’s antioxidant.” Lipoic acid is particularly important as the main regenerator of glutathione, which is by far the most important antioxidant in the human body. (Unfortunately, glutathione itself cannot be taken as a supplement, as it is broken down by the digestive system.)
Most antioxidants come from the class of phytochemicals called flavonoids, of which there are at least 4000. All are antioxidants, and about 50 are found in foods. Many flavonoids are polyphenolic plant pigments that give fruits, vegetables, and berries their bright colors of red, orange, yellow, blue, or purple. These compounds are necessary for the proper functioning of vitamin C, and they are potent antioxidants in their own right.
Among the flavonoids most beneficial to humans is EGCG (epigallocatechin gallate), which is found in green tea; it is among the most promising natural anticancer agents known. Diosmin and hesperidin (found in citrus fruits) and troxerutin (derived from a compound found in buckwheat and the Japanese pagoda tree) are exceptionally effective in combating chronic venous insufficiency. And quercetin (commonly found in rinds and barks) combats allergic reactions and stimulates immune function.
A potent mixture of flavonoids is found in an extract of leaves of the ginkgo tree, Ginkgo biloba. This is one of the most widely prescribed medicinal agents on earth, known for its ability to combat dementia, peripheral arterial disease, vertigo, and tinnitus, among others.
Some phytochemicals called carotenoids are believed to have antioxidant properties, although this is controversial. Carotenoids are plant pigments found in certain red, orange, or yellow fruits and vegetables. The most abundant one is the vitamin A precursor beta-carotene, which occurs predominantly in carrots and other orange and yellow vegetables and fruits, as well as in green leafy vegetables. Two other important carotenoids are lutein (found in dark green leafy vegetables, especially spinach), which protects against eye diseases, and lycopene (found primarily in cooked tomatoes, but also in guavas, papayas, and watermelons), which protects against prostate cancer.
Resveratrol—A Uniquely Important Antioxidant
A very important nonflavonoid, noncarotenoid antioxidant is resveratrol (a stilbene), which is found principally in grape skins and red wine. Resveratrol protects against heart disease (it’s believed to be responsible for the so-called French paradox), and it is probably anticarcinogenic as well. Most importantly, perhaps, is that resveratrol stimulates a biochemical mechanism, called gene silencing, that increases longevity. Resveratrol greatly increases average lifespan in certain lower organisms, and scientists believe that it may hold longevity benefits for humans as well.
The best way to defend yourself against the diseases and aging caused by free radicals is by eating a healthy diet that’s rich in fresh fruits and vegetables—and by supplementing with high-quality antioxidant nutrients, as about 30% of Americans are currently doing. Bear in mind that antioxidants virtually always work better in combination with other antioxidants than they do individually; hence it is best to supplement with multiple antioxidants.
For those who wish to explore this subject in depth, read The Antioxidant Miracle, by Lester Packer and Carol Colman (John Wiley & Sons, New York, 1999). Dr. Packer, a professor of molecular and cell biology at the University of California, Berkeley, is one of the world’s leading authorities on antioxidants.