‘Men trying to conceive should wear boxers, sleep naked’

• Loose underwear found to reduce sperm damage by 25% compared to tight pants
Are you firing blanks? Are you unable to get your woman pregnant? Hear this: Men who want to become a father should wear boxer shorts rather than briefs – and go to bed in the nude.

Researchers, in a report published yesterday in DailyMailUK online, have found that a man’s choice of underwear makes a big difference to the quality of their sperm. It seems that airier, cooler underpants help preserve vital reproductive cells. And at night, wearing no underwear at all gives the best results.

Scientists from Stanford University in California, United States (US) and the US National Institute of Child Health and Human Development carried out tests on 501 men who were trying to become fathers.

Of the group, those who wore loose boxer shorts during the day and no underwear in bed had 25 per cent lower levels of damaged genetic material/Deoxyribonucleic Acid (DNA) in their sperm compared to those who wore tight pants both at night and during the day.

The researchers, who will present their findings at this week’s meeting of the American Society for Reproductive Medicine in Baltimore, suspect that heat is the reason for the effect.

The scientists, led by Katherine Sapra of the NICHD, will say: “Among men in the general population attempting pregnancy, type of underwear worn during the day and to bed is associated with semen quality.

“Reducing exposure for bed decreases DNA fragmentation; better semen quality parameters are observed in men wearing boxers during the day and none to bed.”

Previous research has also found that men who sit with laptops on their knees for prolonged periods are more likely to have damaged sperm, an impact also thought to be linked to heat.

Male fertility expert Allan Pacey, professor of andrology at Sheffield University, said that tight underwear is bad for sperm production – and encouraged prospective dads to choose loose undergarments.

“We have known for some time that men who increase the temperature of their testicles, either through the heat exposure at work or by wearing tight underwear, have poorer semen quality compared to men whose testicles are cooler,” he said.

Although there is a clear link between underwear and sperm, Professor Pacey said that as yet there is no definitive proof that it affects birth rate.

“What has never adequately been shown is whether men can improve things by changing the choice of their underwear, but this study – although quite small – goes some way to suggest that is true,” Pacey said.

“What we really need to see is whether switching to looser underwear makes their partners get pregnant more often or quicker than they would have done had the men continued to wear tight underwear.

“Having said that, switching underwear is hardly a risky thing to do, so buying some looser pants might be good advice for would be fathers.”

Meanwhile, the importance of the basic heat factor is perhaps no better conveyed than in a 2012 paper entitled “Mild induced testicular and epididymal hyperthermia alters sperm chromatin integrity in men.” The authors of this paper worked with five 25- to 35-year-old French men who had at least one child to directly test the effect of heat on sperm production and sperm quality.

The five men in the study were asked to wear specially designed underwear for 14 to 16 hours a day for four months. The underwear kept the scrotum and testicles very close to the body (much closer than you’d get with, say, standard boxer briefs) and naturally heated the testicles by a significant amount relative to their normal state.

The men provided a sperm sample at several points leading up to the study, several points during the study and several points after (when they returned to wearing normal underwear). The chart below shows the sperm count and the percent of viable sperm before, during and after the experiment.

By three to four weeks into the experiment, sperm amount and quality had declined significantly. Even more striking, by the end of the study the sperm count for the men in this sample was at virtually zero. By the last visit, only three of the five men had any sperm in their ejaculate.

The good news? Recovery only took a few months: Once the men switched back to cooler underwear, their sperm count and quality returned to normal.

The intervention in this experiment is extreme, and so are the effects. But the general principle seems to carry over to less extreme behaviors. Tight underwear of any type seems to affect sperm count and quality.

One other example comes from a study in the Lancet, a United Kingdom (UK) medical journal, from the late 1990s. It followed 12 men for a year and alternated each of them between tight and loose underwear. The underwear in this case wasn’t anything special — in the loose condition, men wore boxers; in the tight condition, boxer briefs. The researchers could then compare sperm quality for each man across the two underwear types.

During the tight underwear periods, men had sperm counts of only half as much as during the loose underwear periods. Their counts of motile sperm (a measure of quality) were only a third as much during the tight periods. The effects are, of course, much smaller than in the heat-oriented study — these men still had a reasonable amount of sperm at all times — but they’re surprisingly large given the fairly low treatment intensity.