Key Findings
The 2-OHEstrogen metabolites are proposed to be chemoprotective while 2-OHE1 has been shown to be virtually devoid of uterotropic activity and to suppress growth and proliferation of MCF-7 breast cancer cells. The 16a-OHE1 metabolite is associated with increased breast cancer risk attributable to its significant estrogenic activity. Although lignans and dietary fiber may influence endogenous sex hormone production, little is known about how they interact or whether they affect estrogen metabolism and the urinary 2:16a-OHE1 ratio in premenopausal women. This study determined the effects of flaxseed (F) consumption alone and in combination with wheat bran (WB) in premenopausal women. We hypothesized that consumption of these components would increase urinary 2-OHEstrogen excretion and the urinary 2:16a-OHE1 ratio, thereby possibly offering some chemoprotective benefits. Influencing the hormonal environment in a protective fashion may help prevent cancer initiation. The findings suggest that daily consumption of 10 g of ground F may offer some protection against breast cancer in some premenopausal women by significantly increasing the urinary 2:16a-OHE1 ratio.
ABSTRACT
Estrogen is metabolized along two competing pathways to form the 2-hydroxylated and the 16alpha-hydroxylated metabolites. Based on proposed differences in biological activities, the ratio of these metabolites, 2-hydroxyestrogen:16alpha-hydroxyestrone (2:16alpha-OHE1), has been used as a biomarker for breast cancer risk. Women with an elevated 2:16alpha-OHE1 ratio are hypothesized 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 consumption alone and in combination with wheat bran on urinary estrogen metabolites in premenopausal women. Sixteen premenopausal women were studied for four feeding treatments lasting two menstrual cycles each in a randomized cross-over design. During the four feeding treatments, subjects consumed their usual diets supplemented with baked goods containing no flaxseed or wheat 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 16alpha-hydroxyestrone, as well as their ratio, 2:16alpha-OHE1, were measured by enzyme immunoassay. Flaxseed supplementation significantly increased the urinary 2:16alpha-OHE1 ratio (P = 0.034), but wheat bran had no effect. These results suggest that flaxseed may be chemoprotective in premenopausal women.