Researchers poured cold water on the idea that moderate drinking helps prevent heart disease, noting that many studies include teetotalers as a control group but don't ask why they did not drink.

Several major studies have found that light to moderate drinking up to two drinks a day on a regular basis is associated with a lower risk of heart disease. Some have also found a lower risk of some cancers.

When such studies show a higher death rate for abstainers than for moderate drinkers, it may be because of the poor health of some abstainers who recently quit drinking and not because alcohol is good for health, they said.

In the seven studies that included people who have not drunk alcohol for a long time, by choice, there was no difference in rates of heart disease between drinkers and non-drinkers.

"The widely held belief that light or moderate drinking protects against coronary heart disease has had great influence on alcohol policy and clinical advice of doctors to their patients throughout the world," said Tim Stockwell of the Center for Addictions Research at the University of Victoria.

"These findings suggest that caution should be exerted in recommending light drinking to abstainers because of the possibility that this result may be more apparent than real," Stockwell said in a statement.

People may quit drinking for many reasons, including declining health, frailty, medication use or disability.

Writing in the journal Addiction Research and Theory, the researchers said any future studies should be designed to take into account a person's reason for not drinking.

"We know that older people who are light drinkers are usually healthier than their non-drinking peers," said Kaye Fillmore of the UCSF School of Nursing. "Our research suggests light drinking is a sign of good health, not necessarily its cause. Many people reduce their drinking as they get older for a variety of health reasons."