A new study has warned that frequent visits to the sauna may lower men's sperm count, although the effect appears to be temporary.
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In the study, conducted by researchers at the University of Padova in Italy, healthy Finnish men in their 30s with normal sperm counts spent 15 minutes in a sauna two times a week for three months, after which they stopped visiting the sauna.
The sauna sessions lowered the men's sperm counts, and they remained below normal for three months after the men stopped visiting the sauna, compared with the levels at the study's start. After six months, however, sperm counts returned to normal.
The findings make sense because higher temperatures are known to affect sperm production, said Dr. Andrew Kramer, a urologist at the University of Maryland Medical Center.
The testicles hang down from the body in men to cool them, Kramer said.
Men with undescended testicles can have impaired sperm product and fertility, according to the researchers.
However, the new study did not assess the men's fertility, so it's impossible to know whether their fertility was lower during the period they took saunas. A man's sperm count does not always correspond to his fertility, Kramer said.
The study also found that sauna exposure affected the way DNA was packed into the sperm cells, and impaired the mitochondria, the cell's powerhouse. This might explain why sperm production is less efficient during sauna exposure, the researchers said.
However, Kramer said the study doesn't provide enough evidence to say that healthy men shouldn't visit the sauna. The study was small, with just 10 people, so more research is needed to confirm the results.
Additional studies are also needed to look at the effects of sauna exposure on men whose fertility is already impaired, or on boys who haven't yet gone through puberty, said study researcher Carlo Foresta, a professor of endocrinology at the University of Padova in Italy.
The study was published online Feb. 14 in the journal Human Reproduction.