Soy Isoflavones Tied to Improved Metabolic Markers in PCOS

Marlene Busko

August 04, 2016

Young women with polycystic ovary syndrome (PCOS) who took a 50-mg/day soy isoflavone supplement for 3 months had improved levels of metabolic markers in their blood, from triglycerides to insulin, in a small, randomized, placebo-controlled study.

Specifically, compared with women who received placebo, those who received the soy isoflavone supplement for 12 weeks had significantly improved insulin resistance and significantly reduced levels of serum androgen, triglycerides, and malondialdehyde (a marker of oxidative stress).

The research, by Mehri Jamilian, MD, from the Endocrinology and Metabolism Research Center, Arak University of Medical Sciences, Iran, and Zatollah Asemi, PhD, department of nutrition, Kashan University of Medical Sciences, Iran, was published online August 4 in the Journal of Clinical Endocrinology & Metabolism.

PCOS is common among women of reproductive age and is associated with hyperinsulinemia, impaired glucose metabolism, hyperandrogenism, and dyslipidemia, but this is the first trial to examine the effect of soy isoflavone supplements on these measures in this patient population, according to the authors.

The results hint that consuming the equivalent of 500 mL of soy milk a day could improve metabolic markers that are related to risk of diabetes and cardiovascular disease.

And although this is a preliminary study, it suggests that "clinicians should advise all women with PCOS to include soy isoflavones in their diet" — for example, by drinking a glass of soy milk every day or taking a 30- to 50-mg soy isoflavone supplement daily, Dr Asemi told Medscape Medical News in an email.

PCOS Fairly Common; Soy Might Help

According to the US Endocrine Society, an estimated 5 to 6 million women in the United States have PCOS, which is a common cause of infertility, and Dr Asemi noted that about 15% of women of reproductive age in Iran have PCOS.

A pilot study without a placebo group by Romualdi et al reported that women with PCOS who took 36 mg of genistein a day for 6 months lowered their levels of LDL cholesterol (Fertil Steril. 2008;90:1826–1833).

"Other studies have reported a positive impact of phytoestrogens on the glycoinsulinemic assessment of postmenopausal women, obese subjects, and patients with type 2 diabetes," said Dr Asemi.

Thus, the researchers hypothesized that soy isoflavones would have a beneficial effect on the metabolic status of women with PCOS.

They enrolled 70 women between the ages of 18 to 40 (mean age, 27) who were seen in their clinic in Arak from December 2015 to February 2016 and who met Rotterdam criteria for a diagnosis of PCOS (two out of three of aligo- and/or anovulation, clinical and/or biochemical signs of hyperandrogenism, or polycystic ovaries).

The study participants were randomized to take a 50-mg soy isoflavone capsule (containing 37.5 mg genistein, 10 mg daidzein, and 2.5 mg glycitein; 35 women) or a placebo capsule (35 women), each day for 12 weeks.

The women also took metformin at an initial dose of 500 mg/day, which was increased stepwise to a total of 1500 mg/day, Dr Asemi noted. They were also instructed not to take any other nutritional supplements during the study.

The women completed food records and physical-activity records at baseline, 3, 6, 9, and 12 weeks and had blood tests at baseline and 12 weeks.

Compared with the women who received placebo, those who received the soy isoflavone supplement had significantly improved insulin resistance (a significant decrease in serum insulin levels, homeostasis model of assessment-insulin resistance [HOMA-IR], and HOMA-B cell function [HOMA-B] and a significant increase in quantitative insulin sensitivity check index [QUICKI]), as well as significant increases in serum total testosterone, sex hormone-binding globulin (SHBG), free androgen index (FAI), triglycerides, VLDL cholesterol, glutathione (GSH), and malondialdehyde levels.

Biomarker Change From Baseline to 12 Weeks, Soy vs Placebo Supplement

Biomarker Soy supplement group Placebo group P
Serum insulin, µIU/mL -1.2 +2.8 <0.001
HOMA-IR -0.3 +0.6 <0.001
QUICKI +0.0009 -0.01 0.01
Free androgen index -0.03 +0.02 <0.001
Serum triglyceride, mg/dL -13.3 +10.3 0.04
Plasma total glutathione, µmol/L +96.0 +22.7 0.04
Malondialdehyde, µmol/L -0.7 +0.8 0.001

Growing Interest in Soy for Metabolic Health

"The results of the current study may support a direct pharmacological effect of soy isoflavones on the markers of insulin metabolism," Drs Jamilian and Asemi write.

Soy isoflavones may improve markers of insulin resistance by inhibiting protein tyrosine kinases, which play an important role in the regulation of insulin secretion by pancreatic beta cells, they suggest.

"There is growing interest in how adding soy to the diet can help address metabolic syndrome and related health conditions," Dr Asemi notes in an Endocrine Society statement.

"Our findings indicate consuming soy isoflavone regularly may help women with PCOS improve their metabolic and cardiovascular health."

The research was supported by a grant from the vice chancellor for research, Kashan University of Medical Sciences and Arak University of Medical Sciences, as well as the government of Iran. The authors have no relevant financial relationships.

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J Clin Endocrinol Metab. Published online August 4, 2016. Abstract

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