A new meta-analysis of 20 prospective studies on the link between fiber and breast cancer risk has shown that consuming a diet high in fiber is associated with a lower likelihood of developing breast cancer in both premenopausal and postmenopausal women. The results of this study have been published in the journal Cancer.

In addition to providing valuable information on the potential for fiber to help mitigate breast cancer risk, this new paper also dove deeper to help clarify what types of fibers are most beneficial. The authors investigated the details of fiber intake across nearly 2 million women, more than 67 thousand of whom had breast cancer.

Women in the study were analyzed based on either their total fiber intake or the level of a certain type of fiber they consumed. The specific types of fibers that were analyzed were soluble fiber, insoluble fiber, legume fiber, and fiber from cereal, fruit, or vegetables.

The most significant findings were that soluble fiber consumption and total fiber consumption were inversely associated with the risk of developing breast cancer. In other words, the more soluble fiber and the more total fiber women consumed, the lower their chance of being diagnosed with breast cancer.

Those consuming the highest levels of total fiber had an 8% lower risk for developing breast cancer. Based on the relevant science, the authors suggested that fiber may achieve this beneficial health effect by lowering levels of problematic hormones in the blood, such as sex hormones, insulin, and insulin-like growth factor 1.

Though no significant correlation between insoluble fiber intake and breast cancer risk was identified, the authors noted that the direction of the relationship mimicked the direction of the relationships between both soluble fiber and breast cancer risk and total fiber intake and breast cancer risk. Thus, though statistically insignificant, a trend could be seen between higher levels of insoluble fiber consumption and lower levels of breast cancer.

Future research on the specific link between different types of fiber and dose and frequency of intake will likely build on our understanding of how dietary fiber can best be used as a safe and effective patient care way to lower breast cancer risk.