Dietary Flavonoids May Reduce Breast Cancer Risk
Behind the Cancer Headlines®
April 17, 2006
Flavonoids, a class of antioxidants found in green tea, red wine, soybeans, fruit and vegetables, are associated with a reduced risk of breast cancer among post-menopausal women, according to results of the Long Island breast cancer study project. The results are one of the first epidemiologic studies to suggest that these compounds could have a chemoprotective effect among women.
Brian Fink, Susan Steck and Marilie Gammon of the University of North Carolina, Chapel Hill, and other colleagues studied data from a large study of breast cancer incidence and risk factors conducted among women living during the mid-1990s on Long Island, N.Y.
Breast cancer risk was reduced for the highest percentages of total flavonoid intake, compared to the lowest intake of the plant antioxidants. The decreased risk was about 45 percent among post-menopausal women. Risk decreases were not seen in pre-menopausal women. Specific flavonoids – including flavones, flavan-3-ols and lignans – were associated with reduced cancer risks ranging from 26 to 39 percent; other flavonoids, such as flavanones, isoflavones and anthocyanidins, showed no relationship with reduced cancer risk.
"These results are consistent with other studies conducted among Mediterranean women," said Fink. "Few epidemiologic studies have examined whether there is a relationship between breast cancer and dietary flavonoids. Our study proposes that dietary flavonoids can help American post-menopausal women reduce their risk of breast cancer."
The researchers examined data from the Long Island study, which was conducted by Gammon and colleagues between August 1996 and July 1997. The team compared data from 1,434 women with breast cancer to data from 1,440 women who were not diagnosed with the disease.
Flavonols, flavones, lignans and anthocyanidins are all flavonoids, molecules that give plants protection from oxidative damage due to disease and environmental stresses. Flavonoids are classified according to chemical structure, and have been studied for their varying degrees of effectiveness against human diseases, both in treatment and prevention.
"There are no recommended dietary standards for ingestion of flavonoids, and we do not know exactly how these chemicals may work on a cellular level," said Fink, whose work was supported with funding from the National Institutes of Health and the Lance Armstrong Foundation. "Minute differences in chemical structure could determine how a certain natural antioxidant may work to prevent disease, including cancer. More study is needed to determine why certain flavonoids appear to be effective at reducing cancer risk, and others do not appear to have these properties."
Annual Meeting of the American Association for Cancer Research, April 4, 2006, Washington, DC
American Association for Cancer Research (http://www.aacr.org)