Wearing polyester underwear lowers testosterone levels.
"Do you do you believe in the whole like you can't wear a certain type of underwear type thing that it lowers test? I was going to ask like there's like a certain material people avoid like polyester." (said at 0:48:28)
There is no evidence in human clinical trials demonstrating that wearing polyester underwear lowers serum testosterone levels. In the primary experimental study investigating the effects of continuous wearing of polyester versus cotton undergarments over 24 months (conducted in dogs), polyester fabric caused reductions in sperm count and motility, but serum hormone levels (including testosterone, LH, FSH, and prolactin) showed no significant changes (P > 0.05).
- contradicts: Effect of different types of textile fabric on spermatogenesis: an experimental study. (Urological research 1993)
"There were insignificant changes (P > 0.05) in hormones during the study." (abstract, results, passage verified)
pubmedfull study (doi)