Alcohol has long been linked to low sperm quality, in fact, new evidence suggests that as little as 5 alcoholic drinks a week could negatively affect sperm count. Those men drinking more than 25 units of alcohol a week may have even more trouble keeping their sperm cells alive and kicking. Sperm appears to have an inverse dose- response relationship with alcohol, in other words, if alcohol intake goes up then sperm count goes down!
So aim to keep alcohol to a minimum if you value the integrity of your swimmers. However, it is still worth noting that this is one study in isolation, it is not a meta- analysis (a study that looks at all of the research on a particular subject) and therefore does not mean this finding is 100% conclusiv
Medscape, (2014). Alcohol intake tied to low sperm quality, high testosterone. Retrieved 22nd October, 2014, from discount supplements