Higher fiber diets may help reduce circulating estrogen levels, which researchers say is part of the reduction in breast cancer incidence they saw in the new study. Photo by www.BillionPhotos.com/Shutterstock
BOSTON, Feb. 1 (UPI) -- Higher levels of dietary fiber during adolescence and young adulthood was linked to a significantly lower risk of breast cancer, according to a large study.
Most Americans don't get the amount of fiber they should, researchers at Harvard University say, but women should pay particularly more attention.
"From many other studies we know that breast tissue is particularly influenced by carcinogens and anticarcinogens during childhood and adolescence," said Walter Willett, a professor of epidemiology and nutrition at Harvard University, in a press release. "We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk."
For the study, published in the journal Pediatrics, researchers analyzed dietary data from the Nurses' Health Study II collected in 1991 on 90,534 premenopausal women between the ages of 27 and 44, and from follow-up questionnaires completed by 44,263 of the women in 1998 on their high school diets.
The researchers documented 2,833 cases of invasive breast cancer during 20 years of follow-up from the initial questionnaire in 1991. There were 1,118 cases of breast cancer found while following up with the 44,263 women as well.
Risk for breast cancer was found to be between 12 and 19 percent lower among women who ate more fiber in early adulthood. Those who ate more fiber in adolescence saw a 16 percent overall lower risk and 24 percent lower risk of developing the disease before menopause.
For each additional 10 grams of fiber eaten daily during early adulthood, breast cancer risk declined by 13 percent.
"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 Dr. Maryam Farvid, visiting scientist at Harvard Chan School of Public Health. "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 premenopausal breast cancer."