> Food and Nutrition > Vitamins > vitamin E

Anti-Cancer Antioxidants
by author Carmia Borek, PhD

Imagine the cells in your body turning brown just like an apple does when exposed to the oxygen in the air. Not a very glamorous picture, is it? But that’s what happens when the body’s cells are damaged by free radicals.

Free radicals are produced by normal body metabolism and by factors such as exposure to radiation and environmental pollutants. A high-fat diet increases free-radical reactions, as does eating heated and processed oils. However, antioxidants, both made in the body and supplied by the diet, prevent oxidative damage and protect the body from the harmful effects of free radicals.

Powerful antioxidants include vitamins C and E, beta-carotene, selenium and garlic. Nutritional antioxidants have a role in any healthy diet. Green and yellow vegetables, fruits, nuts and seeds all contain antioxidants. A healthy body will produce healthy cells, which is the best strategy for protection against free-radical damage and one more way to help prevent cancer.

Vitamin C

Vitamin C is richest in citrus fruit, the cabbage family, tomatoes, peppers and greens. This important vitamin attacks free radicals, including those from overexposure to sunlight. Vitamin C also boosts immunity and helps produce anti-inflammatory steroids, which adds to its cancer-preventive role.

Diets high in vitamin C-containing fruits and vegetables have been found to cut in half the risk of oral, larynx, esophagus and stomach cancer, and to a lesser extent protect against cervical and breast cancer. One of the dangers of smoking is that smokers rapidly deplete their levels of vitamin C, reducing antioxidant defences while increasing their free-radical burden and cancer risks.

Vitamin E

Vitamin E’s richest natural sources are vegetable oils, nuts and grains. Vitamin E is found in eight forms, and of these, d-alpha tocopherol has the highest antioxidant activity and cancer-preventive potential. Epidemiological studies show that high levels of dietary vitamin E protect against cancer of the larynx, colon, breast, stomach and esophagus.

Selenium

Low intake of the mineral selenium has been linked to higher rates of colon, breast, ovary, prostate, lung and skin cancer. For example, Finnish women with low serum levels of selenium showed a 10-fold higher rate of breast cancer compared with women whose serum levels were high. Diets high in selenium-containing food protected against prostate cancer, and in one multicentre clinical trial, patients who received supplements of 200 micrograms a day had lower incidences of prostate, colon and lung cancer.

Beta-Carotene

Carotenoids are the fat-soluble pigments that give plants their orange/yellow/red colours. Beta-carotene, familiar to us in its orange hue from its high concentrations in carrots and other orange/yellow vegetables and fruit, is a powerful antioxidant; its ability to convert to vitamin A, when this essential vitamin is in short supply in the body, adds to its importance. Other carotenoids found in human tissues are alpha-carotene, from dietary sources such as orange/green vegetables and fruit; lycopene, the red colour in tomatoes; and lutein, abundant in green leafy vegetables. Of the carotenoids, lycopene has the highest antioxidant activity.

In most cases it is best to get antioxidants from food; a diet rich in fruits and vegetables will provide a varied and ample source of beta-carotene, vitamin C and phytochemicals that may reduce cancer risk. It’s possible, but more difficult to obtain vitamin E from the diet in amounts shown to reduce cancer risk. So be sure to take vitamin E supplements in addition to following a cancer-preventive diet.

Garlic’s Cancer-Fighting Potential

Used since antiquity as a medicinal herb, garlic is being validated by modern science as a rich source of antioxidants with anti-cancer activity. Garlic is unique in its wealth of sulphur-containing compounds, which are largely responsible for its health benefits. Other antioxidants in garlic such as flavonoids and small amounts of selenium add to the cancer-fighting capabilities of this herb.

Supportive evidence for garlic’s protective effects keeps coming in. Garlic lovers in Italy and China who consumed a few cloves a day (about 20 grams) reduced the frequency of stomach cancer by close to 50 per cent compared to those who shunned the herb. A US study of 41,000 women showed that a weekly serving of garlic decreased colon cancer rates by 35 per cent. A French study of 345 women reported that a reduced risk of breast cancer was related to the amounts of garlic consumed; the higher the intake, the lower the incidence of the disease.

Conclusion

Antioxidants provide a source of protection against cancer-causing free radicals. As we age, free radical levels in the body rise so that a continuous intake of antioxidants is important to assure our protection. Taken together, antioxidants are helpful but are not a magic bullet against cancer. Along with exercise, a positive attitude and an overall healthful, whole food diet, antioxidants are invaluable tools to defend against cancer-causing cell damage and prolong a healthy life.

Carmia Borek is a research professor at Tufts University School of Medicine in Boston and the author of Maximize our Healthspan With Antioxidants: The Baby Boomer’s Guide (Keats Publishing, 1995).

Source: alive #234, April 2002