This new study used a mouse model to demonstrate that the dietary phytoestrogen enterolactone inhibits estrogen-induced cancer growth and new blood cell formation while genistein does not. Formation of new blood vessels is an important element of cancer progression. Enterolactone, a metabolite of plant lignans, is derived from foods such as flaxseed, whole rye, wheat bran, sesame seeds, and a variety of fruits and vegetables, whereas the isoflavone genistein is found in primarily in soybeans. In the study, breast cancer tumors were induced in mice by transplanting estrogen receptor positive (ER+) breast cancer cells into them. The mice were supplemented with estrogen (estradiol (E2)) to promote tumor growth and fed diets containing enterolactone, genistein, their combination, or a control diet. Both the enterolactone and the combination enterolactone plus genistein diets were found to inhibit estrogen-induced cancer growth and angiogenesis while genistein alone did not. The authors conclude that dietary enterolactone has powerful anti-estrogenic effects on breast cancer growth (even in combination with genistein) while genistein does not.

Enterolactone reduces risk of breast cancer

This study helps explain the mechanism of action by which dietary enterolactone may reduce the risk of breast cancer, especially in postmenopausal women. The role of dietary genistein is less clear (please see our web page on genistein, as well as soy products such as tofu and soy protein isolate). While not entirely consistent, most population studies that have examined the question have found that diets rich in enterlactone are associated with reduced risk of breast cancer.