High dietary fiber intake has been associated with reduced breast cancer risk.
However, few studies have explored the impact by breast cancer tumour subtypes or by racial/ethnic groups, who vary in their fiber intake.
In a study conducted by the Cancer Prevention Institute of California, and published ahead of print in Cancer Medicine, researchers compared women with breast cancer to women without breast cancer and found overall breast cancer risk was reduced by 25% with a high intake of bean fiber, total beans, or total grains.
Greater reductions in risk ranging from 28 to 36% were found for women with estrogen receptor and progesterone receptor negative (ER-PR-) breast cancers in comparison to women with receptor positive breast cancer.
For bean fiber, risk of ER-PR- disease was reduced among foreign-born Hispanics only, who had the highest fiber intake, and consumed the largest proportion of fiber from beans.
Researchers did not find fiber intake from fruits and vegetables to reduce breast cancer risk.
For U.S.-born Hispanics, African Americans and whites, fruits and vegetables were the primary source of fiber intake.
High grain intake reduced risk of ER-PR- breast cancer among white women only.
A large proportion of the study participants did not meet the recommendations for daily fiber intake.
African Americans consumed the least fiber amount of fiber of the three racial/ethnic groups studied.
To conduct this study researchers gathered information on fiber intake from 2,135 women diagnosed with breast cancer participating in the San Francisco Bay Area Breast Cancer Study, a population-based study, and 2,571 women without breast cancer.
According to Esther John, the senior researcher of the study, “Most currently known risk factors for breast cancer apply to hormone receptor positive subtypes. This paper adds to the evidence that dietary factors may play a role in ER-PR- breast cancer which is more frequently diagnosed in African American and Hispanic women.”
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