But until now research had only looked at the beneficial effects of alcohol on the health of older people.

However, benefits such as better general health and psychological well-being can be linked to moderate drinking from the age of 33, says a report in the Lancet.

Dr Chris Power and colleagues from around the world studied 9,605 33-year-old men and women.

Dr Power said: "It might be that drinking one to two glasses of wine a day does help protect against illness.

"We're talking about a very young age group - 33 - and it could be that drinking up to two glasses of alcohol a day can actually protect them."

Health factors

Ill health was judged on three factors - psychological distress, poor general health and long-term illness.

One unit of alcohol is half a pint of beer ...

Those who drank heavily or not at all reported higher rates of ill health than those who drank moderately.

Moderate drinkers were women who drank between six and 20 units of alcohol per week and men who drank between 11 and 35 units.

Heavy drinkers were those who drank more than these amounts.

... or a glass of wine

A unit is equivalent to half a pint of beer, one measure of spirits or one glass of wine.

Although the 11 to 35 units band sounds like a lot of drink, Dr Power explained that a high level of alcohol consumption was chosen on purpose.

"We did not want to comment on the suggested sensible drinking limits," she said.

"We wanted to set levels that would ensure that the top group were undeniably heavy drinkers."

Possible explanations

No one knows for sure exactly how alcohol in moderate amounts produces a beneficial effect that is absent in heavy drinkers or non-drinkers, although there are plenty of possible explanations.

Dr Power offered four. It could simply be that alcohol causes good health. Alternatively, it could be that poor health causes extremes of drinking.

Another option is that heavy drinkers and non-drinkers are prone to ill health, although not necessarily to the same extent, or that they are vulnerable to particular conditions.

However, Dr Power stressed that the study did not aim to find answers to these questions.

She said that the most significant result was finding that there was a link between alcohol and health, and that this link was evident from an early age.

She now hopes to continue the research with the same subjects to see how they progress as they continue to age.