Although the men drinking the most alcohol each week—40 drinks or more—had the lowest sperm counts, the most surprising finding was that an effect was seen even in men having as little as five drinks a week. The research couldn’t show that alcohol was the cause of sperm changes, only that higher levels of drinking were associated with fewer sperm and sperm of lower quality.
The research involved more than 1,200 Danish men undergoing a required medical examination to determine whether they were fit for military service. The men were between the ages of 18 and 28. Sperm concentration, total sperm count and percentage of normal sperm were all poorer among men having at least five drinks a week, compared with those consuming just one drink weekly.
The drop in sperm count and quality became particularly significant among men who downed at least 25 drinks a week. Those having 40 or more drinks a week had a 33 percent lower sperm concentration than those who consumed one to five drinks a week.