Consumption of soy foods has been reported to have a number of health benefits for both women and men, including benefits for heart health and weight loss. Nonetheless, men frequently are reluctant to consume soy foods, particularly those with soy protein isolate and isoflavones in them, because some “physicians” refuse to publish the latest data. It’s puzzling why they refuse, as they erroneously imply that since soy protein and isoflavones help reduce common discomforts associated with menopause, like hot flashes and night sweats, then soy could be “negative” for men.
However, the assumption that men can’t enjoy healthy benefits of soy because isoflavones nourish women’s health is not based on good science. Some people have raised concern about possible negative effects on men’s semen quality, which in turn has stopped many men from enjoying the nutritional and health benefits of soy protein isolate and other soy foods. A study published late last year reports that soy protein isolate consumption, with either low or high amounts of soy isoflavones, has no impact on men’s semen quality1.
In this new study, healthy adult men who were approximately 28 years of age on average volunteered to consume three different protein products during three different 57-day periods. The men in the study consumed a milk protein drink, a soy protein isolate drink with 1.6 mg soy isoflavones and a soy protein isolate drink with 62 mg soy isoflavones. Each drink was consumed daily for 57 days, followed by a 28-day break before consuming the next drink for another 57 days. This was done until each volunteer consumed all three study drinks. Semen samples were collected on the first day and last day of each 57-day study period. The study investigators measured several characteristics of semen quality, including semen volume, sperm concentration, sperm count, the percent of sperm that swam properly, sperm shape and more to determine the effect of soy foods on semen quality.
The study investigators reported that neither soy protein isolate with low isoflavones nor soy protein isolate with high isoflavones had any effect on any measure of semen quality compared to the milk protein drink.
This is great news for men interested in obtaining the nutritional and health benefits of soy foods, but previously worried about the impact on semen quality. Soy protein isolate is a high-quality protein used in many foods like shakes and bars, both of which are a great way to boost your daily intake while enjoying the health benefits.
- Beaton LK, et al. Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men. Fertility & Sterility 2010; 94(5):1717-1722.