The effect of flaxseed and wheat bran consumption on urinary estrogen metabolites in premenopausal women

Estrogen is metabolized along two competing pathways to form the 2-hydroxyl ated and the 16 alpha-hydroxylated metabolites. Based on proposed differenc es in biological activities, the ratio of these metabolites, 2-hydroxyestro gen:16 alpha-hydroxyestrone (2:16 alpha-OHE1), has been used as a biomarker for breast cancer risk. Women with an elevated 2:16 alpha-OHE1 ratio are h ypothesized to be at a decreased risk of breast cancer. Flaxseed, the most significant-source of plant lignans, and wheat bran, an excellent source of dietary fiber, have both been shown to have chemoprotective benefits. Some of these benefits may be attributable to their influence on endogenous sex hormone production and metabolism. We examined the effect of flaxseed cons umption alone and in combination with wheat bran on urinary estrogen metabo lites in premenopausal women. Sixteen premenopausal women were studied for four feeding treatments lasting two menstrual cycles each in a randomized c ross-over design. During the four feeding treatments, subjects consumed the ir usual diets supplemented with baked goods containing no flaxseed or whea t bran, 10 g of flaxseed, 28 g of wheat bran, or 10 g of flaxseed plus 28 g of wheat bran/day. Urinary excretion of 2-hydroxyestrogen and 16 alpha-hyd roxyestrone, as well as their ratio, 2:16 alpha-OHE1, were measured by enzy me immunoassay, Flaxseed supplementation significantly increased the urinar y 2:16 alpha-OHE1 ratio (P = 0.034), but wheat bran had no effect. These re sults suggest that flaxseed may be chemoprotective in premenopausal women.