Fiber Intake Reduces Breast Cancer Risk in Young Adults and Adolescents

Young women and adolescents may be able to decrease their risk of developing breast cancer by maintaining a diet rich in fiber, according to a study published by the American Academy of Pediatrics in February 2016.

Among all women, early adulthood dietary fiber intake was associated with significantly lower breast cancer risk,” the study reads.

The Human Subjects Committee at Brigham and Women’s Hospital and Harvard T.H. Chan School of Public Health in Boston had more than 90,000 premenopausal women fill out a dietary questionnaire in 1991. After 20-year follow-up, 2,833 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, 1,118 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 post-menopausal 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,” said A. Heather Eliassen, associate professor of Epidemiology at the Harvard T.H. Chan School of Public Health, in an interview with CURE. “The benefit of good diet at 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 the journal 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 proved a significant decrease in the chances of developing breast cancer. A recently published meta-analysis of 16 prospective studies showed a five percent lower breast cancer risk for each 10 grams increase of fiber per day. The doctors conducting the new study had even stronger results, with a 13 percent lower risk for breast cancer developing in early adults, and a 14 percent 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 also be a tool for health care providers.

“In terms of providers, this provides more evidence that diet early on is really important,” she said. “One thing is really important is that this provides more evidence how important early exposures are.”

This study comes after an earlier one, the Nurses’ Health Study II (NHSII) cohort, that concluded that fiber intake during adolescence could decrease the risk of proliferative benign breast disease (BBD). Though BBD is non-cancerous, it could increase an individual’s risk for developing cancer later on. The women in the highest quintile of fiber intake proved 25 percent less likely to get BBD than their counterparts in the bottom quintile. The American Academy of Pediatrics study updated this analysis by using a larger number of cases, a longer follow-up period, and also investigating the association between fiber intake and breast cancer hormone receptor status.

The 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, authors on the study said that this kind of diet can also bring about other benefits.
 
“Also, fiber intake assessed by this questionnaire has robustly predicted lower risks of coronary heart disease, type 2 diabetes and constipation,” the study reads.


References

  1. Farvid MS, Eliasson AH, Cho E, et al. Dietary Fiber Intake in Young Adults and Breast Cancer Risk [published March 2016]. Pediatrics.
  2. 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.
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