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Higher fiber intake reduces risk for breast cancer

Consuming more fiber during adolescence and early adulthood could be an important factor in reducing the risk for breast cancer later in life, according to data published in Pediatrics.

“Sex steroid hormone levels are strongly related to breast cancer development, and a diet high in fiber has been hypothesized to reduce [breast cancer] incidence by inhibiting reabsorption of estrogen, thus decreasing circulating levels,” Maryam S. Farvid, PhD, of the department of nutrition at the Harvard T.H. Chan School of Public Health, in Boston, and colleagues wrote. “In most prospective studies, including the Nurses’ Health Study, no significant associations have been seen between fiber intake and [breast cancer] risk.”

To test the hypothesis that higher fiber intake reduces the risk for breast cancer, the researchers evaluated the Nurse’s Health Study II, an ongoing prospective cohort study of 116,430 women who were registered nurses aged 25 to 42 years at the time of enrollment in 1989. Among the 90,534 premenopausal women who completed the dietary questionnaire during the 1991 follow-up, the researchers noted 2,833 invasive breast cancer cases throughout the following 20 years.

Additionally, in 1998, 44,263 of those women answered a questionnaire regarding their diet during high school. Among them, there were 1,118 cases of breast cancer as of the final follow-up. The researchers used multivariable-adjusted Cox proportional hazards regression to determine relative risks and 95% confidence intervals for breast cancer across categories of dietary fiber.

According to the researchers, total dietary fiber consumption during early adulthood was associated with significantly lower risk for breast cancer among all women (RR = 0.81; 95% CI, 0.72-0.91), as were higher intakes of soluble fiber (RR = 0.86; 95% CI, 0.77-0.97) and insoluble fiber (RR = 0.8; 95% CI, 0.71-0.9). There was also an association between total fiber consumption and lower risk for breast cancer among adolescents (RR = 0.84; 95% CI, 0.7-1.01). The average relative risk of fiber intake during adolescence and early adult life, comparing highest to lowest quintiles, was 0.75 (95% CI, 0.62-0.91).

“The findings in this large prospective study support the hypothesis that consumption of foods high in fiber reduce [breast cancer] risk,” Farvid and colleagues wrote. “These results also suggest that dietary fiber intake during adolescence and early adulthood may be particularly important. Our findings are in line with the American Cancer Society guidelines to consume foods rich in fiber such as fruits, vegetables and whole grains, and indicate the importance of adopting these food choices during childhood and early adult life.” – by Jason Laday

Disclosure: The researchers report no relevant financial disclosures.