By Rabiya S. Tuma, PhD
WASHINGTON, D.C. -- April 10, 2006 -- Women with the highest intake of dietary flavonoids may be at reduced risk of ovarian cancer, according to a prospective analysis from the Nurses' Health Study.
Margaret A. Gates, a doctoral student at the Harvard School of Public Health, Boston, Massachusetts, United States, reported the results here on April 4th at the 97th Annual Meeting of the American Association for Cancer Research (AACR).
The researchers analyzed food frequency questionnaires from 66,384 participants in the Nurses' Health Study and evaluated the association between flavonoid intake and ovarian cancer risk. Between 1984 and 2002, there were 344 ovarian cancer cases diagnosed in the population.
Overall there was no relationship between ovarian cancer risk and flavonoids intake. However, when the team compared women in the highest and lowest quintiles for total flavonoid intake they found a significant inverse trend toward decreased ovarian cancer risk with increased intake of flavonoids (P for trend =.04). The relative risk was not significantly different for the two groups (RR=0.78, 95% CI, 0.53-1.13).
Individual flavonoids showed different associations with risk, Ms. Gates said. For example, there was a significant risk reduction detected between the highest and lowest quintiles of kaempferol intake (RR =.66, 95% CI, 0.43-0.89, P for trend =.002). By contrast, the data suggested that myricetin (RR =.74, 95% CI, 0.51-1.06, P for trend =.01) and quercetin (RR=0.83, 95% CI, 0.57-1.21, P for trend =.06) may have a protective effect but did not reach statistical significance.
The estimate of flavonoid intake was based on a 126-item food questionnaire that was administered at enrollment in 1984, as well as in 1990, 1994, and 1998.
Flavonoids, occur naturally in plants and protect them from oxidative damage. Flavonoids are abundant in tea, red wine, soybeans, fruits and vegetables.
"In the Nurses' Health Study population, the primary contributors to kaempferol intake, for which we saw the strongest association, were tea, broccoli and kale," said Ms. Gates. "Some other common foods that contain kaempferol include brussel sprouts, strawberries, grape fruit, and various types of greens." For myricetin, commonly consumed foods in the study population included tea, beans, raisins and walnuts.
Currently there is no recommended dietary intake levels for flavonoids, commented Brian N. Fink, MPH, doctoral candidate at the University of North Carolina at Chapel Hill, who has been studying the impact of dietary flavonoids on breast cancer.
[Presentation title: A Prospective Analysis of Dietary Flavonoid Intake and Epithelial Ovarian Cancer Incidence. Abstract 4013]
Source: US National Cancer Institute, Cancer Therapy Evaluation Program. Retrieved, May 22, 2007.