Consuming soy isoflavones may improve cardiovascular and metabolic health in women with polycystic ovary syndrome (PCOS), results from a new study in the Journal of Clinical Endocrinology & Metabolism has found.

Soy isoflavones, the plant-based estrogens found in the soybean plant, are present in foods such as soy milk and supplements. Researchers from Kashan University of Medical Sciences, Iran, set out to determine the effects of isoflavones on the metabolic profile of women with PCOS. 

The randomized, double-blind, placebo-controlled trial (n=70) included women diagnosed with PCOS between the ages of 18 and 40. They were randomized to either soy isoflavones 50mg daily or placebo for 12 weeks. Study authors measured metabolic, endocrine, inflammation, and oxidative stress biomarkers at the start of the study and after the 12-week intervention phase. 

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Compared to placebo, soy isoflavone significantly lowered circulating serum insulin (–1.2 vs. +2.8 μIU/mL; P<0.001) and homeostasis model of assessment-estimated insulin resistance (–0.3 vs. +0.6; P<0.001). Soy isoflavone administration also increased the quantitative insulin sensitivity check index (+0.0009 vs. –0.01; P=0.01). Study authors noted significant reductions in free androgen index (–0.03 vs. +0.02; P<0.001) and serum triglycerides (–13.3 vs. +10.3mg/dL; P=0.04) vs. placebo. 

Further, there was a significant increase in plasma total glutathione (+96.0 vs. 22.7 μmol/L; P=0.04) and a significant decrease in malondialdehyde levels (–0.7 vs. +0.8 μmol/L; P=0.001) with soy isoflavone vs. placebo. 

No significant effect on other lipid profiles and inflammatory and oxidative stress markers were seen with soy isoflavone consumption. 

“There is growing interest in how adding soy to the diet can help address metabolic syndrome and related health conditions,” said the study’s first author, Zatollah Asemi, PhD. “Our findings indicate consuming soy isoflavone regularly may help women with PCOS improve their metabolic and cardiovascular health.” 

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