Can eating a diet rich in the antioxidant vitamins reduce your risk of cancer, cardiovascular disease or cataracts? Some scientists say "yes." Oxygen damage (oxidation) to your cells may be partly responsible for the effects of aging and certain diseases. Researchers are studying how antioxidants in food may protect against this damage.
As part of their normal function, cells make toxic molecules, called free radicals. A free radical is a damaged molecule – it's missing an electron. Because the free-radical molecule "wants" its full complement of electrons, it reacts with any molecule from which it can take an electron. By taking an electron from certain key components in the cell, such as fat, protein or DNA molecules, free radicals damage cells. Antioxidants that occur naturally in the body and certain foods may block this damage by donating electrons to stabilize and neutralize the harmful effects of the free radicals.
Even though most free radical damage is repaired, a fraction may still remain. The environment is also a source of free radicals caused by ultraviolet radiation or airborne pollutants, such as cigarette smoke.
Eventually, free radical damage may overwhelm the body's natural defenses. As cell damage accumulates, it may contribute to aging and certain diseases. More antioxidant vitamins from one's diet may help counter some of the damage.
Research designed to study free radicals has shown a relationship to a number of diseases. Scientists theorize that low-density lipoprotein (LDL) cholesterol damages the lining of the arteries when it becomes oxidized. Vitamin C, vitamin E and beta-carotene may help protect against the oxidation of LDL cholesterol by neutralizing free radicals.
Evidence from more than a hundred studies suggests that eating fruits and vegetables rich in vitamin C or beta carotene, or taking antioxidant supplements, is linked with a reduced risk of many all cancers. Moreover, scientists suspect that cataracts develop partly as a result of oxidation of proteins in the lens of the eye.
Despite the support for the health benefits of vitamin C, vitamin E and beta-carotene, there are good reasons for not taking large supplemental doses:
- There is no proof of benefit. The evidence for using antioxidant vitamins to lower the risk of chronic disease is preliminary. It has not yet been proved in clinical trials.
- Nobody knows the right dose and researchers do not know which antioxidant, or combination of antioxidants, offers the greatest potential to prevent disease.
- Nobody knows the long-term risks. Generally, vitamin C, vitamin E and beta-carotene are not toxic, yet controlled studies in people typically last less than six months. There is no proof that a daily supplement of 500 or 1,000 IU of vitamin E, for example, carries no risk over five years or a lifetime.
Vitamin supplements should be used wisely. They may have side effects when large amounts are taken. Immune function and the ability to form blood clots may be impaired. Do not exceed the recommended daily doses. Vitamins cannot undo the damage wrought by bad habits. Men in a Finnish study were longtime smokers. Even the protective effects of vitamins suggested in other studies are outweighed by the increased risk smoking incurs.
Vitamins are no substitute for eating well. Scientists suspect that synergistic interactions of vitamins, minerals, and trace elements contained in fruit, vegetables, and grains may play an important role in preventing heart disease. If this belief is correct, the beta-carotene in a well-balanced diet may go farther than the purified form in a capsule. Until nutrient interactions are better understood, the safest bet is to enjoy vitamin-rich foods in abundance and use supplements in moderation.
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