WASHINGTON — Postmenopausal women who consumed higher amounts of the types of flavonoids found in tea and strawberries showed a decreased risk of breast cancer, according to data presented at the annual meeting of the American Association for Cancer Research.
Breast cancer risk was significantly reduced among postmenopausal women in the highest quintile of dietary flavonol intake compared with the lowest quintile, reported Brian Fink of the University of North Carolina, Chapel Hill, who analyzed data on 1,508 women who had breast cancer and 1,556 controls in the Long Island Women's Health Study. However, no reductions in breast cancer risk were observed among premenopausal women, he noted.
The population-based study included women aged 20–98 years in Nassau and Suffolk counties on Long Island in New York, and was conducted between Aug. 1, 1996, and July 31, 1997. The women answered questions about their reproductive histories, environment, occupations, and lifestyles, including dietary intake, during the past year.
When the flavonoids were broken down into specific types, the significant reduction in breast cancer risk applied to flavones, flavan-3-ols, and lignans only; it did not apply to flavanones, isoflavones, or anthocyanadins. Tea provided the main source of beneficial flavonoids in the women's diets, but strawberries and apples were among the other often-consumed sources.
In another study presented at the meeting, women who consumed kaempferol, a flavonoid found in tea, broccoli, and kale, had a reduced risk for ovarian cancer, said Margaret Gates, a doctoral candidate at Harvard University.
Ms. Gates and her colleagues reviewed data on 66,384 women from the Nurses' Health Study who completed baseline food frequency questionnaires in 1984, and again in 1990, 1994, and 1998. The study group included 344 cases of ovarian cancer diagnosed between 1984 and 2002.
Although overall flavonoid intake was not significantly associated with a reduction in risk for ovarian cancer, consumption of kaempferol was associated with a significant (38%) reduction in risk, Ms. Gates said.
Possible inverse associations with ovarian cancer risk were observed for two other flavonoids, myricetin and quercetin, but the results for these flavonoids were not conclusive.
No other known prospective analyses of the protective effects of flavonoids against ovarian cancer have been published, but if additional studies confirm these findings, dietary flavonoids could provide a target for disease prevention, Ms. Gates noted.