Antioxidants
Preliminary studies have suggested that antioxidants are useful in a number of ways in regards to cancer. For instance, they may improve the effectiveness of chemotherapy, decrease side effects of chemotherapy and radiotherapy, and prevent some types of cancer. Sufficient epidemiological studies have shown that ingesting foods high in antioxidants, such as fruits and vegetables, can decrease the risk of many types of cancer. Studies also found that cancer patients have lower levels of anti-oxidants in their blood.
In early 2004, the National Cancer Institute (NCI) released a new fact sheet concerning cancer prevention and antioxidants. Fruits and vegetables are high in anti-oxidants and evidence continued to support the role of vitamins C, E, and A, as well as lycopene and beta-carotene in helping to prevent cancer. However, clinical trial results have not been consistent. The NCI reported that three large clinical trials were trying to better answer the role of antioxidants in cancer prevention.
Free radicals are naturally produced in the body through the normal metabolism of amino acids and fats. These free radicals are unstable molecules that can freely react with and destroy healthy cells. They can bind to and alter the structure of DNA thus leading to mutations and eventually to cancer. Besides cancer, this oxidative stress on the cells can lead to heart, eye, and neurological diseases.
Glutathione, lipoic acid, and CoQ10 are antioxidants formed naturally by the body but their levels decline with age. Vitamins C and E are necessary anti-oxidants but not produced by the body and must be obtained from the diet. The most common antioxidants are the vitamins A, C, and E. Additional antioxidants are natrol, found in grapes and wine; selenium; and melatonin. Flavonoids consist of a large family of antioxidant compounds found in fruits and vegetables. Among the well-studied flavonoids in terms of cancer prevention are catechins from green tea, genistein from soy, curcumin from turmeric, anthocyanosides from blueberries, and quercetin from yellow vegetables. More recent studies have added clack beans to the list of foods high in antioxidants and a 2003 study in Rome reported that women who ate dark chocolate showed some antioxidant benefits.
Although controversy will surround the topic of supplemental antioxidants for some time, there is little if any controversy that dietary levels of antioxidants are useful in preventing cancer. Because of this evidence, the American Cancer Society suggests five servings of fruits and vegetables each day.
Antioxidants in foods are a valuable addition to a healthy diet and steps can be taken to preserve the antioxidant content of foods until they are ready to be ingested. Keeping fruits and vegetables refrigerated or in a cool, dry place helps to slow down the natural breakdown by enzymes that begins to occur as soon as the foods are picked. Fruits and vegetables should not be trimmed or cut until they are ready to be consumed to prevent unnecessary exposure to oxygen. Cooking by steaming, microwaving, or stir-frying in small amounts of fat for short amounts of time also helps to preserve the vitamin content of foods. If liquids are used to cook fruits or vegetables, do not add fat while cooking if you are planning to discard the liquid before eating the fruits or vegetables, to avoid losing the fat-soluble vitamins that may be in the liquids. Finally, it is important to remember that the skin of some fruits and vegetables contains a higher vitamin content than the inner parts, such as the skin of an apple (Wardlaw and Kessel).
Research suggests that consumption of antioxidant-rich foods reduces damage to cells and biochemicals from free radicals. This may slow down, prevent, or even reverse certain diseases that result from cellular damage, and perhaps even slow down the natural aging process. This is the basis for the free-radical theory of aging.
High doses of vitamins and minerals can be toxic. The National Academy of Sciences has suggested safe upper intake levels for adults for some antioxidants. These limits are 2,000 milligrams of vitamin C per day from both foods and supplements combined, 1,000 milligrams of vitamin E per day, and 400 micrograms per day of selenium from both supplements and foods. It is not known how higher levels than these will affect healthy persons.