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Health: Men who wear boxer shorts produce more sperm

Loose-fitting underwear may benefit sperm production in men. At least one study by Jorge E. Chavarro from Harvard T.H. Chan School of Public Health in Boston now published in the journal "Human Reproduction". The scientists analyzed blood and semen samples from 656 men between the ages of 32 and 39 who had visited Massachusetts General Hospital with their partner for fertility treatment. In addition, the test subjects were asked to indicate which type of underwear they had preferred to wear in the past three months.

Men who preferred to dress in boxer shorts - this applied to about half of the test subjects - had an average of 25 percent higher sperm concentration than the other participants. They also had 33 percent more floating sperm in their ejaculate, and they had a higher total sperm count. This difference was particularly pronounced compared to men who preferred tight-fitting shorts or briefs.

In return, the scientists found higher concentrations of the follicle-stimulating hormone (FSH) in the blood of those participants who apparently couldn't win that much boxer shorts. The sex hormone is produced in the pituitary gland and stimulates the production of sperm in the testes. The researchers suspect that the body of men in tight underpants tries in this way to compensate for the lower sperm count.

The study cannot answer the question of why boxer shorts apparently have an advantage in terms of sperm production. However, earlier studies have found indications that tight underwear could increase the temperature in the testicles and thus impair the formation of sperm.

However, it remains unclear whether the relationship observed by Chavarro and his colleagues is actually a cause-and-effect relationship. Although the scientists checked their data for various factors that could also influence semen formation, such as the weight of the test subjects or the frequency of sauna visits or hot baths, it is hardly possible to rule out all conceivable influencing variables. If men like to wear particularly tight-fitting jeans, this could also play a role in the eyes of the researchers, as well as the material from which the pants and underpants are made.

In addition, due to the very special sample, the researchers only examined men who already had difficulties having a child with their partner. It remains to be seen whether the result can also be transferred to other men. So far, the findings of similar studies have been inconsistent, explain the researchers. However, her investigation is the first to also examine the level of sex hormones in a large number of men and look for possible damage to the sperm DNA. Incidentally, the latter did not occur more frequently among those who wear tight underpants.