Since humans began drinking alcohol about 10,000 years ago, the benefits and risks have been debated over many a glass of wine.
Associated with more than 200 types of disease and injuries, alcohol is linked with 3.3 million deaths around the world every year.
Then we hear about the protective effects of moderate drinking – from stress relief to to reduced risk of type 2 diabetes, gallstones and heart disease.
Alcohol is both a tonic and a poison, according to Harvard. "The difference lies mostly in the dose."
Now a new analysis of 45 studies and more than 2.9 million people on the potential protective effects of moderate drinking on the heart has exposed flaws in the research design.
For example, when "non-drinkers" are compared with moderate drinkers, the moderate drinkers have reduced risk of heart disease.
But, researchers from Canada's Centre for Addictions Research (CARBC) at the University of Victoria said many of these studies (75 per cent) failed to account for "non-drinkers" who stopped because of alcohol-related health problems.
Naturally, those who have only ever consumed at a very moderate level are likely to have better health outcomes.
"Former drinkers have a significantly increased CHD [Coronary heart disease] risk compared with lifetime abstainers, especially among men," the paper's authors explain.
"These results confirm that former drinkers should not be included in the abstainer reference group because this will artificially suppress CHD risk estimates for all current drinkers."
Drinking alcohol is associated with a risk of developing health problems such as mental and behavioural disorders, including alcohol dependence, major noncommunicable diseases such as liver cirrhosis, some cancers and cardiovascular diseases, as well as injuries resulting from violence and road crashes.
"The study provides grounds for a healthy scepticism around the idea that moderate drinking is good for you," says CARBC director Tim Stockwell.
"We know that people generally cut down on drinking as they age, especially if they have health problems. People who continue to be moderate drinkers later in life tend to be the healthier seniors. They're not sick, or taking medications that can interact with alcohol."
The findings of Stockwell and his colleagues are in contrast to those of another new study, by researchers from Cambridge University, published in the British Medical Journal.
"Our findings, from the most comprehensive study to date of the relation between alcohol consumption and risk of cardiovascular disease, indicate that moderate alcohol consumption is associated with a lower risk of initially presenting with several, but not all, cardiovascular diseases," the authors said.
Stockwell said it was a "great study" but it was flawed.
"But it has a huge weakness unfortunately," he said. "They did not use research protocols to assess drinking but relied on coding of clinical notes by health practitioners who are notoriously bad at recording alcohol histories. Because no standard protocol was used actual meanings of terms like 'non-drinker' will have been all over the place. As a result, they would not have been able to adequately account for former and occasional drinker biases."
Stockwell said that while the risks of low to moderate drinking were small, people should not raise a glass and think it was good for them.
"The notion that one or two drinks a day is doing us good may just be wishful thinking," he said.
What constitutes low-to moderate drinking is another story, as there is no universal consensus.
In Australia, the Department of Health provided the following guidelines:
"For healthy men and women, drinking no more than two standard drinks on any day reduces your risk of harm from alcohol-related disease or injury over a lifetime.
"Drinking no more than four standard drinks on a single occasion reduces the risk of alcohol-related injury arising from that occasion."