No one is quite sure why, but over the past few decades, there has been a major decline in the quality of men’s semen (the fluid that contains the sperm) and fertility rates throughout the industrialized world. 
As you might expect, there’s no shortage of theories, explanations, and proposed solutions. In this article, we’ll look at how sperm may be affected by temperature. In Part II, we’ll explore some other recent discoveries about what lowers sperm quality and quantity, what raises is, and what we can do about it.
- Men who wear kilts have better quality sperm and are more fertile, according to a study published in the Scottish Medical Journal (where else, for a story on kilts?). For a man to produce enough sperm to fertilize an egg, his testicles have to be three degrees (Celsius) cooler than his body. Unfortunately for men, wearing tight pants or underwear increases testicle temperature by as much as 3.5 degrees C, which causes all sorts of problems. Wearing a kilt—especially without underwear—may be the solution, says Dr. Erwin Kompanje, the study’s lead author. “Kilt wearing likely produces an ideal physiological scrotal environment , which in turn helps maintain normal scrotal temperature, which is known to be beneficial for robust spermotaogenesis [sperm production] and good sperm quality.”
- Baby, it’s cold outside. Along similar lines, researchers in Israel found that sperm perform better in the winter and early spring and slow way down as temperatures rise. This increased performance (and faster swimming), increases the chance that the sperm will reach and fertilize the egg, could explain why more babies are born in the fall (the biggest months are September and August, meaning the babies were conceived in November and December). This study was published in the American Journal of Obstetrics and Gynecology.
- Skip the sauna. Italian researchers studied a number of healthy Finnish men in their thirties who all had normal sperm counts. The subjects visited a sauna twice a week for three months, then stopped using the sauna. After the sauna regimen, the men’s sperm counts were low, and stayed that way for as long as six months. The researchers were quick to point out two things: having a low sperm count doesn’t necessarily mean a man isn’t fertile—plenty of men with low sperm counts become dads; and using a sauna should not be used as a method of birth control. The study was published in the journal Human Reproduction.
- We’re surprised that it took so long for someone to try to make money off this, but inventor Josh Shoemaker just created “snowballs,” specially designed underwear that includes pockets for freezable gel packs to keep your boys cool. If you’re having fertility issues, check with your doctor before you put your sex life on ice.
