High Feeding Fiber Can Prevent Breast Cancer

Teenagers who eat more high-fiber foods - especially fruits and vegetables - may have a much lower risk of breast cancer than those who eat less dietary fiber, a new large-scale study led by researchers at Harvard T.H. Chan School of Public Health.

High Feeding Fiber Can Prevent Breast Cancer

Teenagers who eat more high-fiber foods - especially fruits and vegetables - may have a much lower risk of breast cancer than those who eat less dietary fiber, a new large-scale study led by researchers at Harvard T.H. Chan School of Public Health.

"Previous studies on fiber intake and breast cancer are almost all insignificant, and none of them examine diet during adolescence or early adulthood, a period when breast cancer risk factors appear to be very important," says Maryam Farvid, a Harvard-visiting scientist Chan School and lead author of the study. "This work on the role of nutrition in early life and the incidence of breast cancer suggests one of the few modifiable risk factors for premenopausal breast cancer."

The researchers looked at a group of 90,534 women who participated in the Nurses' Health Study II, a long-running large study of factors that affect women's health. In 1991, women - ages 27-44 at the time - filled out a questionnaire about their food intake, and did so every four years after that. They also completed a questionnaire in 1998 about their meals during high school. The researchers analyzed female fiber intake while adjusting for several other factors, such as race, family history of breast cancer, body mass index, weight change over time, menstrual history, alcohol use, and other dietary factors.

The risk of breast cancer is 12% -19% lower among women who eat more dietary fiber early in adulthood, depending on how much they eat. High fiber intake during adolescence is also associated with an overall risk of breast cancer 16% lower and 24% lower risk of developing breast cancer before menopause. Among all women, there is a strong inverse relationship between fiber intake and breast cancer incidence. For each additional 10 grams of daily fiber intake - for example, about one apple and two whole wheat buns, or about half a cup of cooked beans and cauliflower or pumpkin - during early adulthood, the risk of breast cancer drops. 13%. The biggest real benefit comes from fruit and vegetable fiber.

The authors speculate that eating fiber-rich foods may reduce the risk of breast cancer in part by helping to reduce high levels of estrogen in the blood, which is strongly associated with the development of breast cancer.

"From many other studies, we know that breast tissue is strongly affected by carcinogens and anticarcinogens 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 give to our children during this period is also an important factor in future cancer risk." The study is published in the journal Pediatrics.