It's long been thought that tighty-whiteys and other kinds of snug underwear can be bad for men's semen quality, thanks to the warmer temperatures they can cause down below. And a new study out of Harvard University seems to confirm that suspicion. It found that men attending a fertility centre who regularly wore boxers had higher sperm counts and healthier sperm than everyone else.
The researchers looked at semen samples from more than 600 men who were part of a couple seeking fertility treatment at the Massachusetts General Hospital in Boston. In addition to the samples, collected between 2000 to 2017, the men also disclosed various lifestyle habits, including what type of underwear they usually wore.
Fifty-three per cent of the men typically wore boxers. And these men, the authors found, had a sperm concentration that was on average 25 per cent higher than men who said they stuck to jockeys, briefs, or bikinis. They also had a total sperm count an average 17 per cent higher, as well as more mobile sperm.
And interestingly enough, the boxer men also had lower levels of follicle stimulating hormone (FSH), which helps regulate fertility. These differences were still apparent after accounting for factors like age or their level of physical activity.
The researchers theorise that FSH levels were higher in men who wore close-fitting underwear because their bodies were trying to compensate for the lower sperm count.
"Beyond providing additional evidence that underwear choices may impact fertility, our study provides evidence, for the first time, that a seemingly random lifestyle choice could have profound impacts on hormone production in men at both the level of the testis and the brain", senior author Jorge Chavarro, an associate professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health, said in a statement.
The study, according to Chavarro and his team, is one of the largest of its kind, but there are limitations to the findings, which were published Wednesday in the journal Human Reproduction.
Importantly, they only looked at men who were presumingly already having trouble conceiving with their partners. Most men in the group tended to have good sperm quality, but it doesn't rule out the possibility that these findings might not apply to the general population.
Another possible drawback, common to survey research, is that these men only self-reported their underwear preferences. So there's room for having mistakenly identified the underwear habits of the men. Still, the authors think that's unlikely, for fairly obvious reasons. "While we are unaware of studies evaluating the validity of self-reported type of underwear worn, we have no reason to believe this behaviour would be incorrectly reported by men", they wrote.
Even with these minor caveats, it's not as though temporarily changing to boxers is likely to cause any harm to men who are trying to conceive.
"These results point to a relatively easy change that men can make when they and their partners are seeking to become pregnant", said lead author Lidia Mínguez-Alarcón, a scientist at the Harvard T.H. Chan School of Public Health.
Given that men's sperm counts everywhere are continuing to drop, we might need all the help we can get.