Do Antioxidants Really Protect against Breast Cancer?
High amounts of dietary antioxidants may protect women against developing breast cancer, according to a study published this month in the Journal of Nutrition.1
In this new study, researchers obtained blood samples from 150 women newly diagnosed with breast cancer and 150 women with no history of breast cancer. When they compared the two groups, they found that high amounts of total antioxidants in the blood stream were much more common in women without breast cancer. High concentrations of beta-carotene appeared particularly protective.
Results of this type should be interpreted with caution, however, because they cannot determine whether the reduction in antioxidant levels was a cause or an effect of breast cancer. More pertinent information relating to cause-and-effect can be obtained by measuring antioxidant levels in women who do not have breast cancer, and then observing them for a number of years to see who develops the disease and who does not.
Thus far, studies using this more sophisticated design have revealed no clear association between antioxidant levels and risk of breast cancer. While a deficiency of certain antioxidants may predispose women to breast cancer, there doesn’t appear to be one specific antioxidant that is protective in high amounts.2 3 4 If a woman does develop breast cancer, however, she may have a better prognosis if her diet prior to diagnosis is high in vitamin C and beta-carotene.5
Antioxidants are chemicals that eliminate reactive molecules called free radicals. Free radical damage to DNA is thought to be one of the mechanisms by which cancers develop. The major dietary antioxidants are vitamins C, E, and A, selenium, and the carotenes. While there is little research demonstrating that taking these nutrients in supplement form will prevent cancer, one study did show a strong protective effect of 200 mcg of supplemental selenium per day, in the form of high-selenium yeast.6 Fruits and vegetables are the best dietary sources of antioxidants.
Breast cancer is the most common cancer type and the second leading cause of cancer death in American women.
Unfortunately, there is no clear message to give women who want to eat for the most effective breast cancer prevention. While some studies show a benefit from diets containing high amounts of fiber or fruits and vegetables,7 others do not. Perhaps the best long-term strategy for women would be to get regular exercise and to eat a diet low in saturated fat and alcohol, and high in fruits, vegetables, and fiber. Although it is still debated whether this lifestyle and diet will prevent breast cancer, it is likely to reduce risk of heart disease, diabetes, and osteoporosis.
1. Ching S, Ingram D, Hahnel R, et al. Serum levels of micronutrients, antioxidants and total antioxidant status predict risk of breast cancer in a case control study. J Nutr 2002;132:303–6.
2. Michels KB, Holmberg L, Bergkvist L, et al. Dietary antioxidant vitamins, retinol, and breast cancer incidence in a cohort of Swedish women. Int J Cancer 2001;91:563-7.
3. Verhoeven DT, Assen N, Goldbohm RA, et al. Vitamins C and E, retinol, beta-carotene and dietary fibre in relation to breast cancer risk: a prospective cohort study. Br J Cancer 1997;75:149-55.
4. Hunter DJ, Manson JE, Colditz GA, et al. A prospective study of the intake of vitamins C, E, and A and the risk of breast cancer. N Engl J Med 1993;329:234–40.
5. Jain M, Miller AB, To T. Premorbid diet and the prognosis of women with breast cancer. J Natl Cancer Inst 1994;86:1390-7.
6. Clark LC, Combs GF, Turnbull BW, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 1996;276:1957–63.
7. Challier B, Perarnau JM, Viel JF. Garlic, onion and cereal fibre as protective factors for breast cancer: a French case-control study. Eur J Epidemiol 1998;14:737–47.
Matt Brignall, ND, is in practice at the Seattle Cancer Treatment and Wellness Center and at the Evergreen Integrative Medicine Clinic in Kirkland, WA. He specializes in integrative treatment of cancer. He is a contributor to Healthnotes and Healthnotes Newswire.
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