True or False: The Style of a Man’s Underwear Affects His Fertility
The style of underwear a man wears may affect his fertility, but to date, studies on the subject have not been conclusive or exhaustive. To cover all their bases, men who are trying to conceive may want to opt for loose-fitting underwear—or even none at all. Male infertility contributes to about half of all cases when a couple can’t conceive. Most often, it is caused by a problem with the sperm itself, such as a low sperm count, poor motility (non-active or slow moving sperm), or abnormally shaped sperm. Factors that negatively affect sperm development and motility include drug and alcohol abuse , diabetes , and bacterial infections. Environmental factors include toxic exposure to chemicals or radiation and overheated testicles. The reasons for many cases of low sperm quality go unresolved. As a matter of routine, many fertility clinics suggest that men trying to conceive should wear boxer shorts instead of briefs or tight-fitting underwear. Why? Briefs position the scrotum closer to the abdominal cavity, which may slightly raise its temperature. Increased scrotal temperature can reduce sperm production and motility. But the evidence supporting the boxers-over-briefs advice is pretty weak.
Evidence for the Health Claim
A few studies have shown a decrease in sperm concentration and motility when subjects wore tight-fitting underwear compared to loose-fitting underwear (such as boxer shorts). It is worth noting that most of these studies were conducted on very small numbers of subjects. One study published in the Lancet
included nine subjects; another published in Reproductive Toxicology
studied only two subjects. However small, both of those studies concluded that wearing tight-fitting underwear does increase scrotal temperature enough to significantly reduce sperm count and motility. Neither of these studies, though, suggested that the deleterious effect on sperm was long-lasting. One of the largest studies supporting the claim was conducted on 50 men at Leibig University in Germany. Its results indicated that high scrotal temperatures (defined as near body core temperature) negatively affected spermatogenesis (the development of mature sperm cells). The German study, published in Human Reproduction
, measured scrotal temperatures on men wearing cotton jockey briefs, cotton boxer shorts, or no underwear, and compared the temperatures after the men completed physical activity (walking for 45 minutes on a treadmill), and after they sat in a fixed position for 45 minutes. The study found significantly higher scrotal temperatures while the subjects wore jockey briefs versus boxers, regardless of activity level, and the lowest scrotal temperatures when the subjects wore no undergarments.