Turns out, certain styles of men's underwear may inhibit production of sperm.
According to new research led by Harvard TH Chan School of Public Health, men who most frequently wore boxers had significantly higher sperm concentrations and total sperm counts when compared with men who did not usually wear boxers.
Lead author, Lidia Minguez-Alarcon, said, "These results point to a relatively easy change that men can make when they and their partners are seeking to become pregnant."
For this study, researchers collected information and semen samples from 656 men who were part of couples that were seeking treatment at a fertility centre.
The men, who were between the ages of 32 and 39, completed a survey that included questions about the style of underwear they wore in the previous three months. Options included boxers, jockeys, bikini, briefs, and other.
Men who wore boxers also had higher percentages of motile sperm or sperm that are capable of moving through the female reproductive system and fertilizing an egg. The most significant difference in sperm concentration was seen between men who wore boxers and men who wore jockeys and briefs.
In addition, analysis of blood samples collected from 304 of the study participants showed that men who wore boxers had 14 percent lower levels of follicle stimulating hormone (FSH) compared with men who didn't wear boxers.
FSH is known to play an important role in male fertility and is associated with sperm production.
The simultaneous presence of lower sperm counts and higher FSH among men wearing tight-fitting underwear suggests the presence of a compensatory mechanism. In that, the decreased sperm production among men in tighter underwear signals the brain to boost production of hormones that stimulate the activity of the gonads to try to increase sperm production.
The full findings are present in the journal--Human Reproduction.