Dietary fiber in teen years may lower later breast cancer risk

For girls and young women, getting a lot of fiber could pay off decades later with lowered risk of developing breast cancer.

Researchers analyzed data on more than 44,000 women participating in a long-term study and found those who ate the most fiber during high school and early adulthood were about 20 percent less likely to develop breast cancer by middle age than those who ate the least fiber in their youth.

There’s reason to believe that dietary fiber could affect developing breasts in ways that impact long-term cancer risk, but no one has ever followed-up over such a long period, the authors note in the journal Pediatrics.

“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 Farvid of the Harvard T.H. Chan School of Public Health in Boston. “Therefore, it seems high-fiber diet in early life would be important in terms of breast cancer prevention.”

Foods high in fiber contain many other nutrients, which may have played a role, but most known breast cancer risk factors as well as the overall quality of the women’s diets were taken into account, Farvid said. Yet the association with fiber remained.

The researchers used data from the Nurses’ Health Study II, which included more than 90,000 premenopausal women who completed a dietary questionnaire in 1991, when they were 27 to 44 years old. Eight years later, 44,263 of them also completed a questionnaire about their diets when they were in high school.

In early adulthood, women who got the least dietary fiber consumed an average of 12 grams per day, compared to 26 grams per day for those who got the most fiber, and amounts were similar among the teens.

Fiber intake influences circulating hormone levels, and hormone levels during the adolescent period of breast development may impact later breast cancer risk, she said.

Women who get more fiber as young adults also tend to carry healthy eating habits into later life, she noted.

Ideally this fiber comes from fruits and vegetables, but it can also come from cereals or fortified foods, Blackwell said.