Drinking three or more cups of coffee could dramatically reduce fertility for men, a new study has indicated.
Researchers at Massachusetts General Hospital in Boston found that men who drank more than 265 milligrams of caffeine per day - about three eight-ounce cups of coffee - were only half as likely to conceive via IVF than couples where the male partner regularly consumed less than 88 milligrams over the same period.
According to the Telegraph, the researchers told an annual meeting of experts in the field of reproductive medicine that caffeine may harm sperm at a molecular level.
The study also indicated that men who drank around a pint and a half of beer a night could see their fertility improve.
Men consuming at least 22g (three units) of alcohol per day were found by researchers to be more than twice as likely to reproduce through IVF as teetotallers.
NHS guidelines indicate that men should drink no more than three-to-four units of alcohol a day. A strong pint of beer or cider (5.2% ABV) measures around three units.
"High male caffeine consumption appears to reduce couples' chance of achieving a clinical pregnancy, while male alcohol consumption appears to enhance their chances," lead author Dr Anatte Karmon said.