Drinking modest amounts of alcohol may affect the semen quality of young men, according to a new study.
“Young men should try to avoid habitual alcohol intake of more than 5 units weekly and especially more than 25 units weekly, which may be beneficial not only for their general health but their semen quality as well,” Tina Kold Jensen, Professor of Research at the Department of Environmental Medicine, University of Southern Denmark, Copenhagen, Denmark, told ConsultantLive.
One unit of alcohol was defined as the equivalent to 1 beer, 1 glass of wine, or 1 shot of alcohol.
“We also found that increasing alcohol consumption the week preceding the visit was associated with changes in reproductive hormones, especially a significant increase in serum free testosterone and reduction in sex hormone binding globulin,” Dr Jensen said.
The researchers stated that, to their knowledge, this is the first study among healthy young men with detailed information on alcohol intake. Dr Jensen said, “Previous studies have not found adverse effects of low alcohol intake (fewer than 5 units per week), however, they only assessed average intake. We assessed daily intake the week preceding the semen delivery.”
Dr Jensen added: “We think we found a strong association because we asked the men about intake last week and then extrapolated to a normal week. We know that normal sperm take 3 months to mature. Normal consumption is a better marker than just last week’s consumption.”
The cross-sectional, population-based study asked 1221 men to fill out a questionnaire on whether the previous week was a “normal” week of alcohol consumption and then studied the 553 who stated that it was. These men, age 18 to 28 years, all had undergone a medical examination between 2008 and 2012 to assess their fitness for military service, which is compulsory in Denmark.
Sperm concentration, total sperm count, and percentage of spermatozoa with normal morphology were negatively associated with increasing habitual alcohol intake. This association was observed in men reporting at least 5 units in a typical week but was most pronounced for men with a typical intake of more than 25 units per week.
Men who had a typical weekly intake of more than 40 units had a 33% reduction in sperm concentration compared with men who had an intake of 1 to 5 units per week. Binge drinking was not independently associated with semen quality.
“We do not know how much of a direct effect on semen quality was due to the adverse effect of alcohol on spermatogenesis, but we adjusted for other lifestyle factors, such as smoking, diet, and exercise,” said Dr Jensen. “But it may be a certain lifestyle associated with alcohol intake that is harmful to semen quality.”
The researchers think that even moderate alcohol consumption could be a contributing factor in the low sperm counts reported among young men. Whether semen quality is restored if alcohol intake is reduced remains to be seen, they stated.
The researchers reported their results in the October 2, 2014 issue of the British Medical Journal Open.
Jensen TK, Gottschau M, Madsen JOB, et al. Habitual alcohol consumption associated with reduced semen quality and changes in reproductive hormones; a cross-sectional study among 1221 young Danish men. BMJ Open. 2014;4:e005462 doi:10.1136/bmjopen-2014-005462.