The study, published in the journal BMJ Open, examined 1,200 Danish male military recruits between the ages of 18 and 28 years, all of whom underwent a medical examination between 2008 and 2012.
As part of the assessment they were asked about their drinking habits and invited to provide sperm and blood samples.
The researchers found that for men, who habitually drank heavily, there was a clear link between alcohol intake and quality of sperm, reports femalefirst.co.uk.
The research found the effects occurred when more than 7.5 units of alcohol a week were consumed; the average pint of beer contains around 2.3 units, while some lagers are stronger than this.
"This is, to our knowledge, the first study among healthy young men with detailed information on alcohol intake, and given the fact that young men in the western world (drink a lot), this is of public health concern, and could be a contributing factor to the low sperm count reported among (them)," researchers said in the study.
The more a man drank, the less sperm he made and the more abnormal it was in shape and size; the effect was apparent after just 7.5 units a week - although it was particularly strong after 37.5 units a week.
Hence it is advised that men don't regularly consume more than 21 to 28 units of alcohol a week.