'Tighty whities' really do damage men's fertility: Study of 27,000 men confirms tight briefs impact sperm quality and sexual function

Published: 05:46 EDT, 5 November 2026 | Updated: 05:46 EDT, 5 November 2026 The question of 'boxers or briefs' has divided men for decades. Now, a study has finally revealed the best option for men concerned with their fertility. Scientists from the University of Science and Technology of China enlisted almost 27,000 men, who self–reported wearing either loose or tight underwear. An analysis of their semen revealed that both quality and quantity were lower among men who preferred wearing 'tighty whities'. 'TU [tight underwear] was associated with poorer semen quality and a higher prevalence of erectile dysfunction and premature ejaculation,' the team explained. 'Choosing LU [loose underwear] may represent a simple, modifiable approach to help protect semen quality and sexual function.' The question of 'boxers or briefs' has divided men for decades. Now, a study has finally revealed the best option for men concerned with their fertility (stock image) The participants were asked about their underwear preference – including loose boxers, or tight Y–fronts, thongs, or box briefs. Next, the men provided a semen sample for analysisIn recent decades, studies have shown that men's semen quality has significantly declined around the world. Several contributing factors have already been identified – including lifestyle choices, environmental exposures, and occupational hazards. However, until now, whether or not your choice of underwear impacts your fertility and sexual function has remained unclear.'To our knowledge, few large–scale studies have directly tested whether underwear type is associated with scores on questionnaires for ED [erectile dysfunction] or PE [premature ejaculation],' the team explained in their study, published in the Asian Journal of Andrology. To get to the bottom of it, the team enlisted 26,836 men. First, the participants were asked about their underwear preference – including loose boxers, or tight Y–fronts, thongs, or box briefs. Next, the men provided a semen sample for analysis. An analysis of the samples confirmed that tight underwear was associated with poorer semen quality and quantity. As for why this is the case, the researchers explain that tight underwear increases the temperature inside the scrotum – with knock–on effects. 'Compared with looser underwear, tight briefs increase the temperature inside the scrotum by 0.5°C–1°C,' they said. 'This increase is sufficient to impair the storage of sperm in the epididymis and the final stage of sperm development (spermiogenesis), thereby reducing motility and the proportion of sperm with normal morphology.'In addition, the results revealed a link between tight underwear and sexual dysfunction.They explained: 'In addition to heat stress, prolonged use of TU [tight underwear] can reduce testosterone secretion and lead to sexual dysfunction.'Based on the findings, the researchers suggest that men looking to protect their semen quality and sexual function should reconsider their underwear choices.They concluded: 'Taken together, these findings indicate that TU is a readily modifiable lifestyle factor that may negatively affect spermatogenesis, sperm DNA integrity, and male sexual function.'THE CAUSES OF MALE INFERTILITYThe most common cause of infertility in men is poor-quality semen, the fluid containing sperm that's ejaculated during sex.Possible reasons for abnormal semen include:a lack of sperm – you may have a very low sperm count or no sperm at allsperm that aren't moving properly – this will make it harder for sperm to swim to the eggabnormal sperm – sperm can sometimes be an abnormal shape, making it harder for them to move and fertilise an eggMany cases of abnormal semen are unexplained.There's a link between increased temperature of the scrotum and reduced semen quality, but it's uncertain whether wearing loose-fitting underwear improves fertility.TesticlesThe testicles produce and store sperm. If they're damaged, it can seriously affect the quality of your semen.This can happen as a result of:an infection of your testiclestesticular cancertesticular surgerya problem with your testicles you were born with (a congenital defect)when one or both testicles hasn't descended into the scrotum, the loose sac of skin that contains your testicles (undescended testicles)injury to your testiclesSterilisationSome men choose to have a vasectomy if they don't want children or any more children.It involves cutting and sealing off the tubes that carry sperm out of your testicles (the vas deferens) so your semen will no longer contain any sperm.A vasectomy can be reversed, but reversals aren't usually successful. HypogonadismHypogonadism is an abnormally low level of testosterone, the male sex hormone involved in making sperm.It could be caused by a tumour, taking illegal drugs, or Klinefelter syndrome, a rare syndrome where a man is born with an extra female chromosome.Medicines and drugsCertain types of medicines can sometimes cause infertility problems.These medicines are listed below:sulfasalazine – an anti-inflammatory medicine used to treat conditions such as Crohn's disease and rheumatoid arthritis; sulfasalazine can decrease the number of sperm, but its effects are temporary and your sperm count should return to normal when you stop taking itanabolic steroids – are often used illegally to build muscle and improve athletic performance; long-term abuse of anabolic steroids can reduce sperm count and sperm mobilitychemotherapy – medicines used in chemotherapy can sometimes severely reduce sperm productionherbal remedies – some herbal remedies, such as root extracts of the Chinese herb Tripterygium wilfordii, can affect the production of sperm or reduce the size of your testiclesillegal drugs, such as marijuana and cocaine, can also affect semen quality.Source: NHS