A diet high in fiber may help reduce the risk for breast cancer, researchers report.
The analysis, in the journal Cancer, pooled data from 20 prospective studies of fiber consumption and breast cancer incidence. Some examined total fiber intake; others looked at the varying types of fiber from cereal, fruit, vegetables and legumes; none involved fiber supplements.
Compared with women with the lowest overall fiber intake, those with the highest had an 8 percent reduced risk for breast cancer.
The researchers also found that it was only soluble fiber, the kind that predominates in foods like oatmeal, nuts, beans, peas and lentils, that had a statistically significant association with reduced breast cancer incidence. There was a suggestion that insoluble fiber — the kind found in whole grains and that adds bulk to stool — also reduced the risk, but the effect was not statistically significant. (Both soluble and insoluble fiber are found in varying proportions in most fiber-containing foods.)
Most of the studies concerned postmenopausal breast cancer, but in five reports that examined premenopausal cancer, the effect of fiber was even larger — an 18 percent reduced risk for those who consumed the most.
“These are observational studies that do not prove causation,” said the lead author, Maryam S. Farvid, a research scientist at Harvard. “But there are very few modifiable risk factors for breast cancer, and identifying them, even those that have a small effect, is important.”
