Modest alcohol consumption linked to poorer semen quality

1. Habitual alcohol intake of 5 units/week or more was associated with reduced semen quality.

2. Increased alcohol consumption the week preceding testing was associated with increased serum testosterone levels.

Evidence Rating Level: 3 (Average)

Study Rundown: Excessive alcohol intake is known to have adverse health consequences, but the association between alcohol intake and semen quality is not well understood. The purpose of this study was to determine the impact of alcohol consumption, recent, habitual, and binging, on semen quality and reproductive hormones. This study analyzed semen and blood composition in Danish men aged 18-28 years between 2008 and 2012. Habitual alcohol intake of over 5 units/week (one beer, one glass of wine or 40 mL of spirits equaled 1 unit of alcohol) was associated with a reduction in semen quality, and the effect was most dramatic with weekly alcohol intake above 25 units. In addition, recent alcohol intake the week prior to testing was associated with an increase in serum free testosterone and reduction in sex hormone binding globulin. Binging, defined as consuming 5 or more units of alcohol in a single day, had no independent adverse consequences on semen quality.

This study benefited from utilizing a large national sample of young Danish men who had no knowledge of their fertility potential, thus not affecting their motivation to participate. It was also unique in differentiating recent versus habitual alcohol exposure. Its limitations include its design as a cross-sectional study, precluding assessment of trends. For example, whether men who cut down on alcohol consumption experienced an improvement in semen quality is unknown. Finally, self-reporting of alcohol consumption is often underreported and may have attenuated the association. Overall, this study suggests that even modest alcohol consumption may have consequences on semen quality and reproductive hormone levels and may be a cause of low sperm count in young males.

Click to read the study, published in BMJ Open

Relevant Reading: Effects of alcohol and cigarette consumption on human seminal quality

In-Depth [cross-sectional study]: This study was a cross-sectional population based study of 1,221 Danish men aged 18-28 years who were recruited while receiving compulsory medical examinations for military service from 2008 to 2012. The participants completed questionnaires assessing their alcohol intake recently in the last week, habitually, and binging, and also provided semen and blood samples. The adverse consequences on semen quality, specifically sperm concentration, total sperm count, and percentage of spermatozoa with normal morphology, were most pronounced in men consuming more than 25 units of alcohol/week. In fact, compared to men with an intake of 1-5 units/week, men with a weekly intake greater than 40 units had a 33% (CI_95% 11%-59%) reduction in sperm concentration. Furthermore, recent alcohol intake the week prior to the visit was associated with an increase in serum free testosterone and reduction in sex hormone binding globulin. However, there were no independently associated adverse consequences on semen quality with binging behaviors.

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