It appears that lignans, found in fruits, vegetables, tea, coffee, and cereal products, are as beneficial as isoflavones, found primarily in soy-based foods, when it comes to reducing the risk of breast cancer.  

Researchers from France looked at the risk of postmenopausal invasive breast cancer associated with the consumption of four plant lignans: pinoresinol, lariciresinol, secoisolariciresinol, and matairesinol, and the estimated exposure to two enterolignans: enterodiol and enterolactone.  

Compared with women in the quartile consuming the least total lignans, those in the quartile with the highest intake (>1,395 μg/day) had a 17% lower risk of breast cancer (RR=0.83, 95% CI=0.71–0.95, P

=0.02). Similarly, those with the highest intake of lariciresinol had an 18% lower risk (RR=0.82, 95% CI=0.71–0.95, P

Touillaud MS, Thiebaut AC, Fournier A, et al. Dietary lignan intake and postmenopausal breast cancer risk by estrogen and progesterone receptor status. 