Adolescent girls may be able to reduce their risk for breast cancer by adding more fiber to their diet, according to an analysis of data from the Nurses’ Health Study II.
Previous studies have found no association between fiber intake and the risk of breast cancer. However, those studies looked at fiber intake during adulthood. This study aimed to determine whether eating high-fiber earlier in life is associated with breast cancer risk. The results are detailed in the report “Dietary Fiber Intake in Young Adults and Breast Cancer Risk” (Farvid MS, et al. Pediatrics. Feb. 1, 2016, http://pediatrics.aappublications.org/content/early/2016/01/28/peds.2015-1226).
The Nurses’ Health Study II enrolled 116,430 female registered nurses between the ages of 25 and 42 in 1989.
In 1991, participants completed a questionnaire about their diets, and data on fiber intake were available for 90,534 nurses. In 1997, the women were surveyed about diet during high school, and data on fiber intake were available from 47,263 participants.
Questionnaires sent to participants every two years were used to identify those who had been diagnosed with breast cancer.
As of June 1, 2011, invasive breast carcinoma was diagnosed in 2,833 of 90,534 women. Among the 44,263 women who also provided data on fiber intake during adolescence, 1,118 were diagnosed with breast cancer.
Prior analyses of the Nurses’ Health Study II data found no association between fiber intake and the risk of breast cancer. This analysis, which included a longer follow-up period and more cases, found that eating a high amount of fiber during early adulthood was associated with a significantly lower risk for breast cancer. High fiber intake during adolescence also was associated with a lower risk for breast cancer. The associations remained after controlling for intake of red meat or animal fat.
The authors found that each increase in total fiber of 10 grams per day during early adulthood was associated with a 13% decrease in breast cancer risk.
“Our findings suggest that higher fiber intakes in adolescence and early adulthood are associated with a reduced BC (breast cancer) incidence in both premenopausal and postmenopausal women,” the authors said in the study. “The associations were apparent for most sources of fiber and were independent of other dietary factors and healthy eating behavior.”
They did note several limitations to their study. First, the population was not a random sample of U.S. women. In addition, participants were asked to recall what they ate during adolescence years later.
In a related commentary “Increased Fiber Intake Decreases Premenopausal Breast Cancer Risk” (Pediatrics. Feb. 1, 2016, http://pediatrics.aappublications.org/content/early/2016/01/28/peds.2015-4376), Kathleen K. Harden, M.D., and Kimberly L. Blackwell, M.D., question the validity of data on adolescent dietary habits collected when the women were in their 30s and 40s. Still, they say, “It is reasonable for pediatricians to encourage a high fiber diet and include decreasing breast cancer risk as one of the potential benefits.”