How much drinking is healthy?

People who have a few drinks a week tend to live a bit longer than teetotallers, but even moderate drinking may raise the risk of certain cancers, a large, new study finds.

The research is the latest to look at the question: What level of drinking might be "healthy"?

Drink in moderation

It's a complicated issue to study, and that's led to some confusing public health messages, the researchers noted. The new report does not put those questions to rest. But experts said it does suggest that if people already drink, they would be wise to minimise it.

The findings were published online in the journal PLOS Medicine.

According to The Heart and Stroke Foundation South Africa, if you drink alcohol, you should do so in moderation. They recommend not more than two drinks per day for men and one drink per day for women.

It also suggests people shouldn't seek health benefits by having that second glass of wine each night, said lead researcher Andrew Kunzmann, of Queens University Belfast, in Northern Ireland.

The study, of nearly 100 000 older US adults, found that lifelong light drinkers were somewhat less likely to die over the next nine years. That was in comparison to both non-drinkers and heavier drinkers.

"Light" drinking was defined as one to three drinks per week for both men and women, a drink being a 12-ounce (340mg) beer or a five-ounce (142mg) glass of wine, for example.

Kunzmann stressed that the results do not prove that light drinking, itself, brings any health benefits.

"We urge caution in interpreting these results," he said.

Studies contain flaws

There could be many other things about light drinkers, higher incomes, better diets or higher exercise levels, for example, that explain their greater longevity. Kunzmann said his team tried to account for as many of those factors as possible, but couldn't weigh everything.

A researcher not involved in the study was more blunt. "It's probably not the light drinking," said Timothy Stockwell, who directs the Canadian Institute for Substance Use Research at the University of Victoria. "It's probably something else about those people."

But what about the evidence tying light to moderate drinking to a lower risk of heart disease?

Over the years, many studies have suggested that benefit, but they've had flaws, Stockwell said. One major issue, he explained, is that former drinkers are often lumped in with "non-drinkers" and some of those former drinkers may have quit for health reasons or concerns about their drinking. In his own research, Stockwell has found that when you account for those study flaws, the "benefits" of moderate drinking disappear.

Kunzmann agreed that the former-drinker issue is a problem in many studies. But older adults in this study were asked about their lifetime drinking habits and death risk was lowest among people who'd been, on average, light drinkers their whole adult life. Over nine years, nearly 10% of the study participants died, while almost 13% developed cancer, the findings showed.

No consensus on 'low risk'

Compared with light drinkers, lifelong non-drinkers were about one-quarter more likely to die. Meanwhile, the risk was 19% and 38% higher, respectively, among men and women who drank heavily. ("Heavy" was defined as two to three drinks per day, for both sexes.) On the other hand, the risk of developing cancer tended to inch up the more often people drank – especially for alcohol-related types, such as cancers of the throat, mouth, oesophagus and liver.

So, when the researchers looked at the combined risk of developing cancer or dying, light drinkers still came out on top, but not by much: Non-drinkers were 7% more likely to develop cancer or die than light drinkers were. That risk was 10% higher among heavy drinkers, and 21% higher among "very" heavy drinkers (three drinks or more per day). 

For now, Stockwell said, there is no scientific consensus on what a "low-risk" level of drinking might be. But he agreed with Kunzmann on the bottom-line message: If you already drink, minimise it and don't start drinking more because you think alcohol is good for you. "It's unlikely you'll become less healthy by cutting down on your drinking," Stockwell said.

Take this quiz to find out if your drinking can be affecting your health. 

Image credit: iStock

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