Scientists Warn Men Over Forgotten Risk of Protein Supplements

Protein powder has become almost ubiquitous with the fitness lifestyle, with roughly 25 percent of gym users using the supplements. However, many of us are not aware of the impacts these supplements can have on our health, particularly on male fertility.

As reported by the World Health Organization, infertility affects roughly 1 in 6 people worldwide, with male infertility accounting for up to half of these cases. However, many of us—particularly men—are unaware of how our lifestyles can influence our reproductive health.

"In the context of male fertility, the concern is over the increasing use of protein supplements," Meurig Gallagher, an assistant professor at the Institute of Metabolism and Systems Research at the University of Birmingham in the U.K., told Newsweek. "The main concern is the high levels of the female hormone estrogen that comes from both whey and soy protein supplements.

"Too much female hormone can cause problems with the amount and quality of sperm that a man can produce. Many protein supplements that can be bought have been found to be contaminated by anabolic steroids, which can cause reduced sperm count, shrunken testicles, and erectile dysfunction, among other things."

In a recent study, published in the journal Reproductive BioMedicine Online, Gallagher and his team investigated whether young adults were aware of the potential impacts of supplementation on infertility.

"In our study the majority of people were young adults aged 18 to 25 attending university," Gallagher said. "The widespread use of protein supplement use—79 percent of men, 56 percent of women surveyed—in this population is particularly concerning in the context of fertility."

The team found there was a significant lack of awareness around male reproductive health in general in the population of young adults surveyed. "While people were aware of the problems associated with anabolic steroid use, very few understood that gym protein supplementation can have negative effects," Gallagher said.

While the majority of research has focused on how protein supplements impact men, women may also be impacted by the hormonal changes brought on by having too much protein powder.

"Just like for men, anything that changes the natural hormone rhythms of the body can have negative impacts such as weight gain, changes in insulin levels, or other side effects," Gallagher said. "It is unclear as of yet how protein supplementation impacts women's fertility as little research has been done. As with any dietary supplement it is important to speak with a healthcare professional before starting, particularly if you are trying to conceive."

However, the impact of these plant-based hormones on the human body is still up for debate. "The review paper [itself] admits that there are very few studies," Jose Antonio, CEO of the International Society of Sports Nutrition and professor of exercise science at Nova Southeastern University, in Florida, told Newsweek. "The treatment duration in the four human trials [is] akin to watching the first pitch of a baseball game and then making a judgement about [how] they pitch in the ninth inning.

"The fact that up to 70 percent of the population in the USA is overweight or obese is probably the better thing to study vis a vis fertility."

Therefore, it is important not to be put off going to the gym because of this data. The concern here is specifically over protein supplementation taken in excess. "People should try and educate themselves about any form of supplementation they take, whether that is protein, vitamins or anything else," Gallagher said. "In general, most data would suggest it's better to eat unconcentrated natural food sources of protein, as these are also less likely to be contaminated at a high level with any environmental pollutants. For example, if you are eating a routine diet, roast chicken would be a good source of protein as opposed to a concentrated protein bar or shake."

The study highlights the need for more awareness and conversation around male fertility, as well as further research into the impacts of eating too much protein powder for both men and women.

"In the meantime, there is a real and immediate need to educate all people, but particularly young men, about male fertility and potential negative effects," Gallagher said.

Update 11/24/2023, 5:06 a.m. ET: This article was updated to include comments from Jose Antonio.