Studies comparing loose vs tight underwear
Loose-fitting underwear gives your body the space it was designed to have.
Harvard Study (2018)
A landmark 2018 study from the Harvard T.H. Chan School of Public Health found that men who wore loose-fitting underwear had up to:
- 25% higher sperm concentration
- 17% higher total sperm count
- Lower levels of follicle-stimulating hormone (a marker associated with impaired sperm production)
compared to men who regularly wore tighter styles.
The Problem
Most men never think twice about their underwear.
Yet research suggests they should.
Tight underwear can:
- restrict natural movement
- increase friction
- trap heat close to the body.
Studies comparing loose vs tight underwear found up to:
The reason? Temperature regulation.
Sperm production is highly sensitive to heat.
An earlier study published in the British Journal of Urology showed that men wearing boxer shorts experienced up to 0.5°C lower deep scrotal temperatures compared to those wearing tighter underwear.
Research suggests that increases in scrotal temperature may affect sperm production.
The body is designed to regulate temperature naturally – but tight underwear may interfere with that process.
Loose-fitting underwear
At Son of John, we use lightweight, shirt-grade cotton that enhances airflow and reduces heat retention. Combined with a relaxed silhouette, this allows for:
- Better ventilation
- Less friction
- Reduced unnecessary pressure
- Natural temperature balance
A small change.
SUPPORTED BY
The studies referenced compare loose- and tight-fitting underwear in general. Individual results may vary.
