Lignans are naturally occurring plant compounds with antioxidant activity that also have mild estrogen-like effects in the body. They are found in foods such as flaxseed, sesame seeds, whole grains, rye, broccoli, soybeans, pumpkin seeds, and some berries.
A large prospective study published in the Journal of the National Cancer Institute (2007;99:475-486) followed more than 58,000 postmenopausal French women and found that those with the highest dietary intake of lignans had a 17% lower risk of breast cancer than women with the lowest intake. The participants were not taking soy isoflavone supplements, and lignan intake was estimated using a detailed dietary questionnaire.
Another study published in Cancer Causes & Control (2006;17:1253-1261) compared the diets of more than 3,000 women with breast cancer to over 3,400 women without the disease. The researchers found that women who reported eating more lignan- and isoflavone-rich foods during adolescence had a lower risk of developing breast cancer later in life.
These studies were observational, so they cannot prove that lignans prevent breast cancer. However, they add to the evidence that diets rich in whole plant foods may contribute to better long-term breast health.
