Public Release: 

Soy supplements appear to be safe, beneficial in diabetic men

The Endocrine Society


"Because soy contains phytoestrogens that are similar to the female hormone estrogen, it was not known whether consumption of soy could reduce testosterone levels in men with Type 2 diabetes, who are at increased risk of low testosterone," said the study's lead investigator, Thozhukat Sathyapalan, MD, an endocrinologist researcher at Hull York Medical School, University of Hull, Hull, U.K.


Their study included 210 men ages 55 to 70 who had Type 2 diabetes and a borderline-low total testosterone level: less than or equal to 12 nanomoles per liter (nmol/L) or 345.8 nanograms per deciliter. For three months, the men ate two cereal bars a day, each containing 30 grams of soy protein. The bars in one group of 100 men contained 66 milligrams of soy phytoestrogens, which is equivalent to the amount in soy supplements or in a typical Southeast Asian diet. The second group of 100 men received soy protein bars in which phytoestrogens were removed. Patients were asked to avoid eating foods containing soy.

The men had testosterone blood tests before and after treatment at the same time of day. Both groups experienced an increase in total testosterone level, the investigators reported. On average, testosterone level increased from 9.8 to 11.3 nmol/L in the soy protein-phytoestrogen group and from 9.2 to 10.3 nmol/L in the group receiving only soy protein.



In addition, the phytoestrogen-containing soy protein reportedly led to better improvements in certain cardiovascular risk factors, he said. These included triglycerides--a type of fat in the blood--and high-sensitivity C-reactive protein, which measures inflammation in the body and is a predictor of heart disease risk. Total cholesterol and "bad" (LDL) cholesterol levels rose (worsened) in both groups but not enough to be statistically significant, according to Sathyapalan.

Both soy protein supplements significantly improved diastolic blood pressure (the bottom number in a blood pressure reading) but not systolic blood pressure (the top number).


The study received funding from the Food Standards Agency, which is responsible for food safety in the U.K.

