Large-scale population studies show that diets right in lignans are associated with a reduced risk of breast cancer. Flax and its lignans help protect against breast cancer by altering the metabolism of estrogen and by decreasing cell proliferation, according to findings from a small number of clinical studies. The animal data is strong- flax and its main lignans interfere with cancer processes and inhibit metastasis of mammary (breast) tumors to the lungs and other organs. One animal study found that the combination of flax and tamoxifen was better at decreasing tumor size in mice than tamoxifen alone. Eating flax regularly may reduce breast cancer risk and improve the clinical prognosis for women with breast cancer.

Whole flax seeds and milled flax are excellent sources of lignans. Indeed, flax is the richest known dietary source of lignans. Lignans are phytoestrogens- plant compounds that can affect estrogen metabolism in animals and humans. The main flax lignan is secoisolariciresinol diglucoside (SDG). SDG is converted to the enterolignans or mammalian lignans- namely, enterodiol and enterolactone- by the action of bacteria in the colon. Human and animal studies support a role for flax and its lignans in breast cancer prevention and control.

Dr. Diane H. Morris

Thompson LU, et al. Nutr Cancer. 2006; 54:184-201
Morris DM Flax- A Heath and Nutrition Primer. Winnipeg, MB: Flax Council of Canada, 2007.