A University of Birmingham survey has found that most men are unaware that protein supplements for muscle growth can increase estrogen levels in the body. The study is published in Reproductive BioMedicine Online.
Researchers surveyed 152 gym-goers. 79% of the men used protein supplements, 52% thought about their fertility (ability to conceive), but only 14% thought about how working out at the gym or taking supplements might affect fertility. Interestingly, the women surveyed appeared to be more aware of the effects of exercise and supplements on male fertility.
As the scientists explained, both whey and soy protein can increase men's levels of the female hormone estrogen. Many protein supplements have been found to contain anabolic steroids, which can impair male fertility.
"According to the World Health Organization, infertility is a growing concern: it affects one in six people in the world. Yet there is limited global awareness of the fact that men are responsible for half of these infertility cases," the scientists said.
The authors concluded that people should try to learn more about the effects of the supplements they take. In addition, most evidence suggests that natural food sources of protein, such as chicken meat, are safer than protein supplements.