Can eating a diet rich in the antioxidant vitamins reduce your risk of cancer, cardiovascular disease or cataracts? Some scientists say "yes." although this is an area that is likely to be controversial for some time to come. 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 like cardiovascular disease and some cancers. 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 carotenoids may help protect against the oxidation of LDL cholesterol by neutralizing free radicals. Scientists suspect that cataracts develop partly as a result of oxidation of proteins in the lens of the eye, and some studies have shown that antioxidants might be effective in reducing age-related macular degeneration and the resulting vision loss.
Evidence from more than a hundred studies suggests that eating fruits and vegetables rich in vitamin C or carotenoids is linked with a reduced risk of many cancers. Despite the support for the health benefits of vitamin C, vitamin E and carotenoids, 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. The AHA still does not recommend using antioxidant supplements until there is more complete data. They do, however, recommend eating a daily diet that contains a variety of foods from all the basic food groups (and low in saturated fat and cholesterol) which will provide a rich natural source of these vitamins.
- 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 carotenoids are not toxic, yet controlled studies in people typically last less than six months.