Men who wear boxer shorts have higher sperm concentrations than men who wear tighter fitting underwear, according to recent research published in the journal Human Reproduction.
You can tell the fertility of a man by the underpants he prefers to wear, as researchers continue to gather data on how the style (and material) of underpants affect testicular function (i.e., sperm production).
The study
Researchers surveyed 656 male partners of couples seeking infertility treatment at a fertility center (this was in Boston, MA, USA, between 2000 and 2017). The men were an average age of 35.5 years old.
They completed a questionnaire on what style of underwear they had most frequently worn during the last 3 months using the following categories: ‘boxers’, ‘jockeys’, ‘bikinis’, ‘briefs’ or ‘other’.
For those of us unfamiliar with men’s fashion, the definitions were: "jockeys are longer than briefs, with length falling right above the knee, briefs generally extend to the middle of the thigh.”
They then analysed the men’s semen samples for reproductive hormone levels and neutral comet assays for sperm DNA damage.
What did the study conclude?
They found the type of underwear worn was significantly associated with sperm concentration, total sperm count and total motile count (Table II).
Compared to men who reported not usually wearing boxers (e.g. wore tighter underwear), men who reported most frequently wearing boxers had 25% (95% CI = 7, 31%) higher sperm concentration, 17% (95% CI = 0, 28) higher total sperm count and 33% (95% CI = 5, 41%) higher total motile count.
Men who reported most frequently wearing boxers also tended to have a higher percentage of motile sperm and a higher sperm count, compared to those who did not, although these differences failed to reach statistical significance (check out Table II in the study).
When all the non-boxer underwear types were examined separately, the largest differences in sperm concentration were found for men who reported wearing jockeys and briefs compared to those wearing most frequently boxers.
The differences were less pronounced with other types of underwear (Supplementary Fig. S1).
Men who reported most frequently wearing boxers had higher sperm concentration and total count, and lower FSH levels, compared to men who did not.
Boxer-wearing men had lower FSH hormones
Boxer shorts-wearing men had lower levels of follicle-stimulating hormone (FSH), compared to men who most frequently wore briefs, "bikinis" (very brief briefs), "jockeys" (underwear that finishes just above the knee) or other tight-fitting underwear.
Though FSH stimulates sperm production, the researchers say that these findings suggest that it kicks into gear when it needs to compensate for testicular damage from increasing scrotal temperatures and decreasing sperm counts and concentration.
The impact of material
It goes without saying that the clothing (shirts, trousers and undertrousers) can effect heat regulation.
The type of material also affects heat regulation, as well as at least one other mechanism: electrostatic regulation. Check out these studies on how polyester underwear reduce sperm health.
Men’s fertility epidemic
Researchers have been raising the alarm on the plummeting sperm levels across Western societies in the last century. Environmental and lifestyle factors have been directly linked to poorer testicular function, such as increased exposure to endocrine disrupting chemicals (Bergman et al., 2013; Hauser et al., 2015), higher prevalence of obesity (Finucane et al., 2011; Sermondade et al., 2013), deteriorating diet quality (Wong et al., 2000; USDA, 2017) and elevated scrotal temperatures (Ahmad et al., 2012; Zhang et al., 2015), among others.
Sperm production takes about three months from start to finish, so take the action to switch out your wardrobe, as it may take that long for your sperm quality to improve. For a long time the spotlight (and burden) lay pretty much on female fertility. However, a male fertility crisis has been looming, perhaps just below sight.
If you found this study interesting, check out my full guide to EMFs and your microbiome. It’s free, and you’ll find facts and resources on how electromagnetic fields can impact very basic cellular functions in your body.
References & Resources:
Link to the study: Lidia Mínguez-Alarcón, Audrey J Gaskins, Yu-Han Chiu, Carmen Messerlian, Paige L Williams, Jennifer B Ford, Irene Souter, Russ Hauser, Jorge E Chavarro, Type of underwear worn and markers of testicular function among men attending a fertility center, Human Reproduction, Volume 33, Issue 9, September 2018, Pages 1749–1756, https://doi.org/10.1093/humrep/dey259
Read how polyester underwear lowers sperm counts https://www.melaniechua.com/blog/2023/study-polyester-underwear-decreases-sperm-count-and-motility