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NMU 87 – Soy Isoflavones Improve Key Aspect of Polycystic Ovarian Syndrome (PCOS)

Nutrition / Natural Medicine Update No. 87

with Dr. James Meschino


Topic: Soy Isoflavones Improve Key Aspect of Polycystic Ovarian Syndrome (PCOS)

Source: Journal of Clinical Endocrinology & Metabolism (August 2016)


You know for many years I have encouraged women who suffer from polycystic ovarian syndrome (PCOS) to incorporate soy foods and even soy isoflavone supplements into their overall management. For the most part these recommendations were based on the biological plausibility that they would be helpful, but no actual studies had been performed to prove that soy isoflavones could make a difference.  Well, an impressive study was published in the Journal of Clinical Endocrinology & Metabolism in August of 2016 that showed that soy isoflavone supplementation improved key parameters in the management of PCOS. The study included 70 women diagnosed with PCOS who were 18-40 years old. Participants were randomly allocated into two groups to take either 50 mg/day of soy isoflavones or a placebo for 12-consecutive weeks. The study showed that women ingesting the soy isoflavones showed a significant reduction in blood levels of insulin and testosterone – two major contributing factors to PCOS.

Women with PCOS typically show higher blood insulin levels and increased insulin resistance, which tends to increase production of ovarian cysts. And women with PCOS tend to have higher levels of male hormones, such as testosterone and dihydrotestosterone, which also increase ovarian cyst production. So, isoflavone supplementation reversed these two important PCOS contributing factors and it also reduced their blood cholesterol and triglyceride levels. Two additional important health benefits.  The mechanism through which soy isoflavones achieved these outcomes is related to evidence from previous studies showing that soy isoflavones increase insulin receptor function, which decreases insulin secretion, and isoflavones block a key enzyme that converts the male hormone androstenedione into testosterone and the hormone that converts testosterone into dihydrotestosterone.

Based on those previous studies, I had made the assumption that soy isoflavones would likely benefit women with PCOS, but the study in the Journal of Clinical Endocrinology & Metabolism is the first to confirm this contention. This is an important study because 5-10% of women 15-45 years old suffer from PCOS. When the cysts burst it can be extremely painful, and the infertility rate with PCOS is also very high.  Anything that can prevent the production of ovarian cysts, and facilitate a normalized ovulatory cycle in these cases is helpful, and thus reducing insulin, testosterone and dihydrotestosterone levels with soy isoflavones should now be strongly considered in the nutritional recommendations for PCOS.

There are other nutritional medicine strategies that can also be helpful including:

  • Weight reduction (if overweight)
  • Aerobic exercise – to increase insulin sensitivity and reduce body fat
  • Frequent consumption of cruciferous vegetables (broccoli, brussels sprouts, cabbage, cauliflower, boy choy) – which help regulate estrogen levels and detoxification
  • Supplements that block the conversion of testosterone to dihydrotestosterone, such as Saw palmetto.
  • Essential Fatty Acids – (fish oil, flaxseed oil borage seed oil) – to help reduce inflammation and slow cell division rates.

Together with the ingestion of soy isoflavones, these nutrition and lifestyle factors can help to rebalance the hormonal cascade, improving PCOS management and reducing secondary factors such as acne, male-patterned hair growth, and blood sugar irregularities that are often found in women with PCOS.

I have included the study referenced in the text below.



Mehri Jamilian, Zatollah Asemi. The Effects of Soy Isoflavones on Metabolic Status of Patients With Polycystic Ovary SyndromeThe Journal of Clinical Endocrinology & Metabolism, 2016; jc.2016-1762

Eat Smart, Live Well, Look Great

Dr. Meschino

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