High fiber intake reduces the risk for breast cancer, according to a systematic review published by the American Cancer Society. Researchers compared fiber consumption and types of fiber intake with breast cancer incidence rates. Those who consumed the most fiber had an 8% reduced risk for premenopausal and postmenopausal cancers when compared to those who consumed the least amount of fiber. Soluble fiber from cereals, fruit, legumes, and vegetables showed the strongest association with reduced risk, with the strongest associations observed in fruit fiber. Several possible mechanisms behind the reduced risk include improved blood glucose control and insulin sensitivity, increased levels of sex hormone-binding globulin, and improved composition of intestinal microbiota. The authors noted that high-fiber diets are associated with increased intakes of vitamins, minerals, phytochemicals, and other compounds that offer protective effects against cancer. These results support the American Cancer Society's dietary guidelines to consume fruits, vegetables, whole grains, and other high-fiber foods to reduce the risk for cancer.
Farvid MS, Spence ND, Holmes MD, Barnett JB. Fiber Consumption and breast cancer incidence: A systematic review and meta-analysis of prospective studies. Cancer. Published online April 6, 2020.