Flaxseed and Breast Cancer: What Should We Tell Our Patients?

This review summarizes the authors observations regarding the use of flaxseed to stem breast cancer. Dietary lignans have been identified as potentially protective against breast cancer via estrogen-dependent and independent anticarcinogenic activity. In humans, lignans are metabolized by the gut microflora into enterolignans; enterolactone is the main metabolite. Enterolactone concentrations in serum, plasma, and urine have been used as biomarkers of dietary lignans. Enterolactone levels are negatively associated with breast cancer outcomes. A recent meta-analysis that indicates that enterolactone biomarkers are associated with a statistically significant 28% reduced risk of incident breast cancer. The author suggests that until further information is available, lignan consumption should not be recommended to breast cancer survivors. More data is required regarding the degree to which serum enterolactone concentrations reflect dietary intake of lignans. The bioavailability of lignans from various food sources is not well understood, the colonic environment affects the conversion of dietary lignans to enterolactone, other factors (e.g., smoking, alcohol intake) affect serum concentrations, and the potential effect of endogenous and exogenous hormones on lignan metabolism and excretion has not been fully established. (Editors review)