High Fiber Diet While Young May Reduce Breast Cancer Risk

Adolescent and young adult women who eat a diet high in fiber may reduce their risk for developing breast cancer later in life, according to a new study.

Writing in the journal Pediatrics, researchers from the Harvard T.H. Chan School of Public Health, found that women who ate lots of fruits and vegetables when young had a “significantly lower” chance of developing breast cancer.

"Previous studies of fiber intake and breast cancer have almost all been non-significant, and none of them examined diet during adolescence or early adulthood, a period when breast cancer risk factors appear to be particularly important," said Maryam Farvid, visiting scientist at Harvard Chan School and lead author of the study. "This work on the role of nutrition in early life and breast cancer incidence suggests one of the very few potentially modifiable risk factors for pre-menopausal breast cancer."

For the study, the researchers looked at a group of over 90,000 women who were a part of the Nurses’ Health Study II, a long-running study tracking factors that influence women’s health.

In 1991, women who were 27 to 44 answered questions about their diet. In 1998, they were asked again about their diet when they were in high school.

This formed the basis for analyzing their fiber intake, factoring out other variables like race, family history of breast cancer and others.

They found that among the women who had reported having eaten higher amounts of fiber, there was a 12-19 percent less chance of breast cancer risk. Those who reported eating a lot of fiber in adolescence saw a 16 percent reduction in risk of contracting breast cancer and a 24 percent reduction of getting breast cancer before menopause.

“Among all the women, there was a strong inverse association between fiber intake and breast cancer incidence,” according to a news release about the study.

The researchers found that for every additional 10 grams of fiber eaten, “about one apple and two slices of whole wheat bread,” eaten in early adulthood there was a drop of 13 percent of the risk of getting breast cancer.

They said the fiber from fruits and vegetables had “the greatest apparent benefit.”

While the researchers aren’t certain why fiber reduces the risk of breast cancer, they suspect it helps reduce estrogen levels in the blood. High levels of estrogen is “strongly linked with breast cancer development.”

"From many other studies we know that breast tissue is particularly influenced by carcinogens and anti-carcinogens during childhood and adolescence," said Walter Willett, Fredrick John Stare Professor of Epidemiology and Nutrition at Harvard Chan School and senior author of the study. "We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk."