The following correction was printed in the Guardian's Corrections and clarifications column, Thursday October 26 2006
Our statement below that "one unit [of alcohol] is a glass of wine ..." needs qualifying. A so-called standard glass of 12.5cl of 12% wine contains about 1.5 units. The increasingly common 17.5cl glass contains over 2 units, rising to nearly 2.5 at 14%.

Doctors should not encourage men in good health who drink moderately to give up alcohol, according to researchers. Quite the opposite: a 16-year study of nearly 9,000 men in the US found that a regular tipple lowered their risk of heart attack.

Men who drank between one and a half and three units of alcohol a day on average had nearly a third of the risk of suffering heart attacks faced by healthy men who stayed off the booze. One unit is a glass of wine or a half-pint of beer.

"We only looked at really healthy people," said Eric Rimm at Harvard school of medicine in Boston, "but even beyond their already low risk, people who drink moderately can lower their risk of [heart attack] still further. [Doctors] should not tell them to stop drinking."

Dr Rimm's team selected 8,867 of the healthiest men from a study of more than 50,000 healthcare professionals. All were non-smokers with a body mass index of less than 25, who exercised regularly and had a healthy diet. Starting in 1986, the researchers monitored the subjects' self-reported alcohol consumption and whether they suffered a heart attack during the following 16 years. Of the sample, 106 died of a heart attack.

Men who averaged between zero and one unit of alcohol a day suffered a similar risk of heart attack to teetotallers, while those who drank three units a day or more had a slightly reduced risk.

But the most impressive protection from heart attack was in men who drank moderately. An average of 0.5 to 1.5 units a day nearly halved the risk compared with abstainers, while those who drank between 1.5 and 3 units a day suffered nearly a third of the risk. The results appear in the current issue of Archives of Internal Medicine.

Dr Rimm said alcohol increased levels of the "good" cholesterol HDL in the blood and reduced the risk of clotting.