Which Underwear Is Best for Sperm Count? Study Offers New Answer

Wearing loose underwear could boost a man's sperm count, according to Harvard researchers.

Tight underwear has the opposite effect, the study indicated.

Scientific evidence already suggests that the scrotum being subjected to high temperatures could negatively affect a man's reproductive organs, so the team wanted to understand if underwear had a similar effect.

Researchers recruited 656 men aged between 32 to 39 who were members of couples seeking fertility treatment at the Fertility Clinic at Massachusetts General Hospital.

The participants donated samples of sperm, blood, and provided information including the style of underwear they had worn most often in the past three months, picking from either boxers, jockeys, briefs or 'other'.

Of the 53 percent who said they wore boxers, their semen samples had 25 percent higher concentrations of sperm and 17 percent higher total sperm counts when compared to men who wore other styles of underwear. Their sperm also appeared to be better at swimming. The biggest difference was found in men who wore jockeys or briefs versus boxers.

Further analysis of the blood from 304 participants showed men who primarily wore boxers had lower levels of follicle stimulating hormone (FSH)—which is linked to male fertility and sperm production. This suggests the bodies of men who wore tight pants were creating more FSH to try to make the testicles work harder at producing sperm. That's what Dr. Allan Pacey, professor of andrology at the University of Sheffield, who was not involved in the study, told Newsweek.

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Lidia Mínguez-Alarcón, research scientist at Harvard T.H. Chan School of Public Health and author of the paper published in the journal Human Reproduction, told Newsweek: "We found that men who wear tight underwear have lower sperm counts, which was consistent with previous literature."

Wearing looser underwear could therefore help boost the sperm counts of men, argued Mínguez-Alarcón, as sperm takes around 90 days to grow.

Dr. Channa Jayasena, lecturer in reproductive endocrinology at Imperial College London, told Newsweek fertility is steadily declining for reasons that are unclear, and there are currently no treatment for boosting sperm counts.

"For the first time, they have shown that men wearing boxer shorts have healthier sperm quality, and lower levels of a hormone [FSH]; low FSH is a good thing because it means the body is making enough sperm. This reinforces the view that men with fertility problems should avoid tight underwear."

But others were less convinced by the findings. Dr. Eric A Widra, a chief medical officer at Shady Grove Fertility who was not involved in the study, told Newsweek: "Although this study shows differences in sperm count and hormone function between men wearing boxers and briefs, it is critically important to note that both groups had normal sperm counts and hormone values.

"Their numbers are about average for fertile males, and we would not expect different pregnancy rates from men in boxers or briefs. It does suggest that men who have borderline sperm numbers and who wear briefs may see a small improvement with these lifestyle changes."

Dr. Peter N. Schlegel, professor of urology at Weill Cornell Medicine, who did not work on the research, commented the study was limited by the fact the subjects were all from a male fertility clinic rather than the general population.

"It is not clear that the underwear caused the lower sperm production, but the lack of confounding factors [differences in the two study groups] suggests the effect may be real," he said.

Pacey said the results mirror the findings of a study his team published in 2012. That investigation showed men who wore boxer shorts were significantly less likely to have low motile sperm counts.

"And in a further paper in 2014, we showed that type of underwear was unrelated to sperm morphology [a measure of sperm size and shape], which the authors also confirm in this study," he said.

He flagged the study was not a randomized controlled trial, meaning there is therefore no proof a man's underwear would affect his fertility.

"It's also important to note the study is not implying underpants are a major cause of infertility–in fact, fertility has not been measured," he said. "There is a big difference between measuring aspects of sperm quality (as done in this study) and measuring fertility."

"However, I think it is a reasonable low cost and low risk lifestyle change that men with poor sperm quality can undertake to potentially improve their semen quality," he said.