Quiet. Warm. Relaxing. Soothing. How can a hot tub or a steaming hot bath possibly be bad for your health? Well they are…for men. They reduce male fertility. Big time.
The History of Heat and Fertility
Elevated temperature has been a recognized cause of impaired sperm production since the time of Hippocrates. Even a simple fever can hurt the sperm factory. In the 1940’s, Dr. Martha Voegeli, a Swiss doctor in India, reported a simple heat regimen for male contraception. Her protocol involved having men sit in a hot bath (116o F) for 45 minutes daily for 3 weeks. Six months of infertility resulted from this exposure, after which normal fertility returned. The most modern example of heat affecting fertility is the postulated heating of the scrotum with laptop computers. Kind of makes you wonder about the effect of the recent triple digit heat wave in the U.S. on nationwide baby making efforts.
Heat: The Real Deal
These stories intrigued me and led me to publish a study on the effects of hot tubs and baths on male fertility. Specifically, we asked whether the withdrawal of such exposures in men with poor semen quality could lead to improvements in semen quality. We also looked for factors that might influence the response to stopping the exposure to heat.
In our study, a series of men were evaluated before and after exposure to wet heat in the form of baths and tubs. Among them, 45% responded favorably to withdrawal to heat exposure with a mean increase in moving sperm counts of almost 500%. If sperm were money, they would be rich! Some men started out with no sperm (azoospermia) and had return of sperm to the ejaculate. The problem is that it took 3 to 6 months to see the change, reflecting the time it takes to make and ejaculate sperm. Among those who didn’t respond, many were tobacco users (makes sense: take a tub, drink wine and light one up).
We concluded that tubs are toxic to semen quality and that the toxicity is reversible in many cases. The reversibility takes time though. The New York Times release of our paper’s findings included a figure of a man in a hot tub thinking about how much better hot tubs are than condoms or birth control pills for contraception.
Although a hot tub or bath may be the last thing on your dehydrated mind as you swelter in the summer heat wave, keep this advice in mind this autumn as you consider romantic ways to make hay.