Effect of Dietary Flaxseed on Serum Levels of Estrogens and Androgens in Postmenopausal Women

January 1, 2008 Human Health and Nutrition Data 0 Comments

Effect of Dietary Flaxseed on Serum Levels of Estrogens and Androgens in Postmenopausal Women

Year: 2008
Authors: Sturgeon, S.R. Heersink, J.L.
Publication Name: Nutrition and Cancer
Publication Details: Volume 60; Number 5; Pages 612-618.


Flaxseed is a rich source of dietary lignans. Experimental studies suggest lignans may exert breast cancer preventive effects through hormonal mechanisms. Our aim was to study the effects of flaxseed on serum sex hormones implicated in the development of breast cancer. Forty-eight postmenopausal women participated in a 12-wk preintervention postintervention study. Participants consumed 7.5 g/day of ground flaxseed for the first 6 wk and 15.0 grams/day for an additional 6 wk. Non-significant declines were noted over the 12 wk (95% confidence intervals) for estradiol (pg/ml), estrone (pg/ml), and testosterone (pg/ml): 4.4 (12.6 to 3.9), 3.3 (7.7 to 1.2), 4.7 (17.8 to 8.5), respectively. Changes tended to be more pronounced in overweight/obese women, particularly for estrone (6.5, 11.9 to 1.2; P = .02). Our results suggest that dietary flaxseed may modestly lower serum levels of sex steroid hormones, especially in overweight/obese women. (Author's abstract)
Endogenous levels of estrogens and androgens are believed to play a central role in the etiology of breast. Lignans, naturally occurring compounds structurally similar to sex steroid hormones, are found in flaxseed. Studies suggest that lignans exert breast cancer preventive effects through hormonal mechanisms. There is limited information on the effect of plant lignan intake on serum sex hormone levels in humans. To date, three intervention studies have evaluated the impact of dietary flaxseed consumption on serum levels of sex hormones in postmenopausal women yielding inconsistent results. In this study, consuming 7.5 g of flaxseed per day for 6 wk and 15 g of flaxseed for an additional 6 wk resulted in modest, non-statistically significant declines in serum levels of testosterone, estrone, and estradiol but not SHBG in this group of postmenopausal women. In the subset of overweight women, the mean reduction of 6.5 pg/ml for estrone was statistically significant. A decline in testosterone after flaxseed consumption was noted consistent and suggest that lignans can bind and promote excretion of testosterone in the bile. This study has several limitations, in that is was relatively small and thus small changes in serum sex hormones due to flaxseed are difficult to detect. The study lacks a placebo control group. The findings do suggest that consumption of one to two tablespoons of flaxseed per day for 12 wk may favorably influence estrogen and androgen concentrations, particularly in overweight/obese women. The authors stress that additional research focused on clarifying the effects of flaxseed on breast biology is warranted. Such research is important because of the promotion of flaxseed as having breast cancer preventative effects and its increasing widespread availability. (Editor's comments)

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