In a new study published in the Journal Pediatrics, researchers have announced that increasing dietary fiber in young women may help protect them against breast cancer. Researchers from the Harvard T.H. Chan School of Public Health in Boston analyzed data on more than 44,000 women who participated in a long-term study.
Those who ate the most fiber during early adulthood were found to be 16 to 20 percent less likely to develop breast cancer by the time they reached middle age. It was also estimated that the risk of breast cancer decreases by 13 percent for every 10 grams of fiber consumed daily during early adulthood.
While this line of reasoning is not new, this is the first time there has been follow-up of the theory over such a long period. “Most of the studies that evaluated association between dietary fiber intake in midlife or later, have not noted any significant association,” said lead author Maryam Favid. “Therefore, it seems high-fiber diet in early life would be important in terms of breast cancer prevention.”
In addition to high fiber, these foods contain many other nutrients which may play a role. However, even though the overall quality of women’s diets were taken into account the high-fiber connection remained.
Data from the Nurses’ Health Study II was used by the researchers. It included more than 90,000 premenopausal women who completed a questionnaire about their diets when they were between 27 and 44 years old, back in 1991. Eight years later, 44,263 of them completed an additional questionnaire about their diets while in high school.
By 2011, 1,118 cases of invasive breast cancer had been reported among the women for whom there was high school dietary data.
The women were divided into five groups by the study team, ranked from highest to lowest dietary fiber intake. Those consuming the least dietary fiber in early adulthood got an average of 12 grams per day, compared to 26 grams on the other end of the scale.
Beneficial dietary fiber consumed while young included both soluble fiber such as oat bran, that attracts water and slows digestion, and insoluble fiber such as wheat bran, that adds bulk and helps foods pass more quickly through the digestive process.
An accompanying article by Kimbelry Blackwell, MD and Kathleen Harnden, MD, stated that “soluble fibers are believed to decrease intestinal cholesterol absorption,” and that there is evidence that these byproducts may have estrogenic effects. “Dietary fibers may reduce circulating estrogen levels through changes in the gut microbiome and increased excretion of estrogens in the gastrointestinal tract,” they wrote.
Average Americans today eat 10 to 15 grams of fiber on a daily basis. According to the National Library of Medicine, most should be getting 20 to 35 grams daily.