The Effects of Soy Isoflavones on Metabolic Status of Patients With Polycystic Ovary Syndrome.

Randomized, double-blind, placebo-controlled trial in women aged 18 to 40 years with polycystic ovary syndrome diagnosed by Rotterdam criteria. The active soy isoflavone group included 35 participants, with a matched placebo group of 35 women, enrolled at Kosar Clinic in Arak, Iran.

Women received 50 mg/day soy isoflavones orally as capsules for 12 weeks. The supplement provided 37.5 mg genistein, 10 mg daidzein, and 2.5 mg glycitein; the comparator was an identical placebo capsule.

Overall, 12 weeks of soy isoflavone supplementation produced a favorable metabolic, hormonal, and oxidative stress profile in women with PCOS. Insulin resistance markers improved, with significant time-by-group effects for insulin and HOMA-IR both < .001, and hormonal status improved as SHBG increased from 38.0 ± 8.7 to 41.9 ± 7.9 nmol/L, FAI fell from 0.12 ± 0.08 to 0.09 ± 0.06, and mFG scores declined from 14.7 ± 4.6 to 13.5 ± 4.1. Triglycerides also improved relative to placebo (time-by-group = .04), while total cholesterol, LDL-cholesterol, HDL-cholesterol, and hs-CRP showed no consistent between-group benefit. Oxidative stress markers improved, including higher nitric oxide, TAC, and GSH and lower MDA, with no adverse effects reported.

The trial was small, single-center, and short in duration, which limits confidence in durability and generalizability. Findings apply to reproductive-age women with PCOS in one Iranian clinic, and diet and physical activity were monitored rather than tightly controlled, leaving some residual confounding risk.