A recent Harvard study found men who wore boxers had about 25% more sperm than those who wore briefs

• The boxers vs. briefs debate may be over. According to experts, wearing tight underwear like briefs creates a temperature increase that prevents sperm from growing and developing properly.
• A recent Harvard study found that men who wore looser underwear, like boxers or boxer-briefs, had about 25% more sperm in their collected samples.
• Researchers believe that tight underwear could jeopardize the fertility of men who already suffer from low sperm counts.
• However, it's possible to reverse damage caused by wearing tight underwear by switching to a less confining option.

Following is a transcript of the video.

Boxer shorts were introduced in the 1920s for, well, boxers. The underwear were loose around the legs, giving boxers the freedom they needed. Then, about a decade later, briefs came into the world,

Offering a sleeker, tighter fitting option, and also launching into effect that age-old question: boxers or briefs? And it turns out, there might be a clear winner, after all.

Yes, wearing tighty-whities can lower your sperm count.

You read that right: wearing tight underwear can lower your sperm count. Turns out, if underwear is too tight, it pushes the testicles closer to the body. Increasing their temperature in the process. And that's bad news for the sperm inside. You see, a man's sperm production is at its best when his testicles are cooler than his core body temperature 2 to 4 degrees Celsius cooler, to be exact.

That's why the testes hang down, away from the body, for most mammals. So when you wear tight underwear, the resulting increase in temperature can damage the sperm, and potentially your fertility as well. Scientists have been studying this link between body heat and fertility for years, several studies show that men who work under hot conditions, like bakers and ceramic oven operators, are more likely to have fertility issues than men who work cooler jobs.

But ovens are much warmer than the human body. So it wasn't until recently that researchers discovered that yes, even a small increase in temperature - from wearing tight underwear - can cause problems In 2018, Harvard researchers released the largest study on the subject to date. They analyzed 656 men seeking treatment at fertility centers and recorded their daily underwear preference: "Boxers" or "non-boxers," like briefs and jockeys.

Sure enough, men who wore boxers had 33% more mobile sperm - the kind that can swim and successfully fertilize an egg. They also just had more sperm in general - about 25% more in their collected samples. But the researchers also found something they weren't expecting. Men in the "non-boxers" group had higher levels of something called a follicle stimulating hormone, or FSH. FSH is released by the pituitary gland to help boost sperm production in the testes. So, researchers think that an increase in FSH levels could be the body's way of compensating for low sperm production.

And while both groups of men still had plenty of sperm needed to conceive a child, researchers found that tight underwear might jeopardize the fertility of men who already suffer from low sperm counts.

Luckily, young, healthy men tend to produce sperm continuously, so it's possible to reverse damage caused by wearing tight underwear, simply by switching to a less confining option.