Flaxseed intervention and reproductive endocrine profiles in patients with polycystic ovary syndrome: an open-labeled randomized controlled clinical trial.

The short version

This 12-week open-label randomized controlled trial with 70 women explored whether daily flaxseed intake could shift reproductive hormone patterns in polycystic ovary syndrome (PCOS), a common endocrine condition affecting 6 to 15 percent of women of reproductive age. PCOS involves hyperandrogenism (elevated androgen hormones) and disrupted ovulation, often accompanied by a low or borderline follicle-stimulating hormone (FSH) that limits egg follicles from fully maturing. Flaxseed is a plant-based food rich in phytoestrogenic lignans (plant compounds structurally similar to estrogen) and omega-3 fatty acids, both proposed to influence the hormone pathways governing follicle development and gonadotropin balance. Seventy women diagnosed with PCOS at a clinic in Ahvaz, Iran were randomly assigned to 12 weeks of either 30 grams of daily milled flaxseed added to salads, yogurt, or cold drinks, combined with standard diet and exercise guidance, or the same lifestyle guidance without flaxseed. Blood tests measuring FSH, luteinizing hormone (LH), anti-Mullerian hormone, estradiol, DHEAS, and androstenedione were drawn at baseline and after 12 weeks using enzyme immunoassays and chemiluminescent assays, timed to each participant's menstrual cycle phase where applicable. FSH rose significantly more in the flaxseed group than in controls (treatment effect 0.87, 95% CI 0.086-1.75, p=0.027), meaning flaxseed users saw a measurably larger increase in this follicle-stimulating hormone than those on lifestyle changes alone. The ratio of LH to FSH also dropped significantly with flaxseed (treatment effect -0.341, 95% CI -0.63 to -0.08, p=0.031), a lower ratio pointing toward more balanced gonadotropin secretion, since an elevated LH/FSH ratio is a hallmark of PCOS. No significant between-group changes appeared for AMH, LH alone, estradiol, DHEAS, or androstenedione, indicating flaxseed's measured effect was specific to FSH and its ratio to LH rather than the broader hormone panel. Weight, BMI, lipids, and blood sugar stayed similar between groups, and no adverse events were reported, suggesting the 30-gram daily dose was well tolerated over the 12 weeks. The authors propose that flaxseed's omega-3 fatty acids and lignans may support follicle-stimulating hormone receptor activity and gonadotropin regulation, though this mechanism was not directly tested in the trial. The open-label design, unavoidable for a dietary intervention, the single-center setting, and the absence of testosterone and insulin measurements limit how broadly the results extend. The authors identify larger, longer randomized trials incorporating androgen and insulin outcomes as the needed next step for confirming flaxseed's role in PCOS management.

Key findings

• In a 12-week trial of 70 women with polycystic ovary syndrome (PCOS, a hormonal condition marked by irregular ovulation and elevated androgen hormones), daily consumption of 30 grams of milled flaxseed alongside lifestyle guidance was associated with a small but statistically significant rise in follicle-stimulating hormone (FSH, the hormone that stimulates egg follicle development) compared with lifestyle guidance alone (p=0.027).
• The ratio of luteinizing hormone to FSH (LH/FSH ratio, a marker often elevated in PCOS) also decreased significantly with flaxseed (p=0.031), suggesting a shift toward more typical gonadotropin hormone balance.
• Other reproductive hormones measured, including anti-Mullerian hormone (AMH), LH alone, estradiol, DHEAS, and androstenedione, did not change significantly between the flaxseed and control groups.
• No adverse events were reported over the 12-week intervention, and body weight, cholesterol, and blood sugar remained similar between groups.
• The trial's open-label design, single-center setting, and modest sample size mean the findings need confirmation in larger, blinded studies that also measure testosterone and insulin.

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