Starting Young With Focus on Fiber May Reduce Breast Cancer Risk Later On

Focusing on a fiber-rich diet at a young age may help lower the risk of developing breast cancer later, according to findings of a new study.

Focusing on a fiber-rich diet at a young age may help lower the risk of developing breast cancer later, according to findings of a new study, which found that among all women, early adulthood dietary fiber intake was associated with significantly lower breast cancer risk.1

Researchers at Brigham and Women’s Hospital and Harvard TH Chan School of Public Health in Boston looked at a group of more than 90,000 women participating in the Nurses’ Health Study II (NHSII), a large, long-running investigation of factors that influence women’s health.

The women filled out a dietary questionnaire in 1991, and after a 20-year follow-up, 2833 cases of invasive breast cancer were documented. Of the original group, about half (44,263 women) filled out a retrospective high school diet questionnaire in 1998. In that group, 1118 cases of invasive breast cancer were reported.

Prior to the study, it was hypothesized that fiber may help reduce the amount of estrogen in the blood, which is strongly linked to the eventual development of breast cancer.

An association between fiber intake and breast cancer in postmenopausal women was also found during the study, though the correlation was not statistically significant. Previous similar studies among older women and their fiber-related breast cancer risks have almost all been nonsignificant, according to this study’s authors.

The findings about younger women, however, are much stronger.

“This work stems from the interest of trying to discover when in a person’s life one is exposed to carcinogens,” explained A. Heather Eliassen, associate professor of epidemiology at the Harvard TH Chan School, in an interview with Oncology Nursing News. “The benefit of a good diet at an early age is really important.”

Breast tissue may be “particularly susceptible to carcinogenic exposure” during childhood and adolescence, according to the study, which cited the atomic bombing of Hiroshima and Nagasaki and radiation treatment of Hodgkin lymphoma as examples.

But that is not to say that there are no dietary changes for older adults that may reduce the risk. A study published in 2015 in JAMA Internal Medical found that a Mediterranean diet supplemented with extra virgin olive oil could reduce breast cancer risk by 68 percent.2

While the results for this fiber study did not show as high a correlation, they still suggested a significant decrease in the chances of developing breast cancer. A recently published meta-analysis of 16 prospective studies showed a 5% lower breast cancer risk for each 10 gram-increase of fiber per day. The doctors conducting the new study had even stronger results, with a 13% lower risk for breast cancer developing in early adults, and a 14% lower risk for adolescents. This proved true for both soluble and insoluble fiber.

“This is a message that women can use, whether it is for themselves or for their kids,” said Eliassen, who also noted that the findings could be a tool for healthcare providers.

The study follows an earlier one involving the NHSII cohort that concluded that fiber intake during adolescence could decrease the risk of proliferative benign breast disease (BBD). Though BBD is noncancerous, it could increase an individual’s risk for developing cancer later on.

Women in the highest quintile of fiber intake proved 25% less likely to get BBD than their counterparts in the bottom quintile. The American Academy of Pediatrics study reported here updated this analysis by using a larger number of cases, a longer follow-up period, and also investigated the association between fiber intake and breast cancer hormone receptor status.

Findings were in line with the American Cancer Society’s guidelines to consume foods rich in fiber, such as fruits, vegetables and whole grains. Further, study authors noted that this kind of diet can also bring about other benefits:

“Fiber intake assessed by this questionnaire has robustly predicted lower risks of coronary heart disease, type 2 diabetes, and constipation.”


  • Farvid MS, Eliasson AH, Cho E, et al. Dietary Fiber Intake in Young Adults and Breast Cancer Risk [published March 2016]. Pediatrics.
  • Toledo E, Salas-Salvadó J, Donat-Vargas C, et al. Mediterranean Diet and Invasive Breast Cancer Risk Among Women at High Cardiovascular Risk in the PREDIMED Trial: A Randomized Clinical Trial [published September 14, 2015]. JAMA Intern Med.