From NewScientist:

Men might want to remember a new rhyme: a drink a day keeps erectile dysfunction away.

Despite traditional views about the effects of booze on male performance, new research suggests that moderate drinking actually protects against impotence in the long term – perhaps for the same reason a glass or two of wine a day cuts the odds of suffering from heart disease.

There is good evidence that excessive drinking can hinder sexual performance after a night out – a phenomenon sometimes called “brewer’s droop”. The effect has been noted for many years: “[Drink] provokes the desire, but it takes away the performance,” Shakespeare reminds us in Macbeth.

But over longer periods, moderate drinking doesn’t seem to be linked to erectile dysfunction, says Kew-Kim Chew, an epidemiologist at the University of West Australia in Nedlands, whose team conducted an anonymous postal survey of 1770 West Australian men.

After accounting for differences due to age, smoking and heart disease – all risk factors for ED – Chew and colleagues found that drinkers experienced rates of impotence 25% to 30% below those of teetotallers.