New research carried out at the Hull York Medical School (HYMS) has found that phytoestrogens – which are similar to the female hormone oestrogen – appear to be safe and beneficial for men with Type 2 diabetes.
Phytoestrogens are found in a variety of foods including nuts, seeds, soy products and whole grains. Some studies have indicated that countries that consume the highest levels of phytoestrogens have the lowest rates of breast cancer and heart disease. However, due to the similarities between phytoestrogens and the female hormone oestrogen, there has also been concern that they may have a negative impact on male fertility.
The results of this latest study were presented at the joint meeting of the International Society of Endocrinology and The Endocrine Society (ICE/ENDO 2014) in Chicago.
Dr Thozhukat Sathyapalan, a HYMS endocrinology researcher based at the University of Hull, and lead investigator of the study, said:
“Prior studies have found that daily consumption of soy reduces the risk of Type 2 diabetes and heart problems. However, men with Type 2 diabetes are already at increased risk of low testosterone, and it was not known whether consumption of soy could further reduce these levels.
“Not only did our study find that soy protein and phytoestrogen supplementation is safe in diabetic men, it may improve their diabetes control and their risk factors for heart disease.”
The study included 210 men aged 55 to 70 who had Type 2 diabetes and a borderline-low total testosterone level. The men ate two cereal bars a day for three months. For half the men, the bars contained 30 grams of soy protein along with soy phytoestrogens. For the remaining half, the soy phytoestrogens were removed so that the bars contained 30 grams of soy protein only.
The research found that both groups of men experienced an increase in total testosterone level. However, soy protein with phytoestrogens improved diabetes control much better than soy protein alone.
In addition, the phytoestrogen-containing soy protein reportedly led to better improvements in certain cardiovascular risk factors. These included a reduction in triglycerides - a type of fat in the blood – and a lowering of ‘high-sensitivity C-reactive protein’, which is a predictor of heart disease risk.
“We did find that cholesterol levels worsened in both groups, but not enough to be statistically significant,” said Dr Sathyapalan.
“The message is that soy protein supplements are safe and beneficial for men with Type 2 diabetes who already have borderline-low testosterone,” he added.
“We don’t know exactly why we saw testosterone levels rise in both groups of men, but it could be a direct effect of soy. We hope that this study will add to the growing body of research on phytoestrogens and help provide clearer advice for patients.”