Virginia Nicholls: Science around potential benefits of moderate alcohol drinking still undisputed

A Canadian study, funded by the Canadian Centre on Substance Use and Addiction, was set up to find flaws in other alcohol studies. And that it did. Photo / Tony Cenicola, The New York Times, File

OPINION

It’s a well-established fact that all things being equal, those that drink lightly to moderately live longer than those that do not drink at all. Yet every so often a “new” study makes headlines by calling this well-researched point into question.

A recent Canadian study purported to debunk long-established science around the potential health benefits of moderate alcohol consumption, sending waves around the world.

In the wake of the study’s publication, the story ran with a headline suggesting the study had refuted “decades of research”.

But the hoop-la has proven somewhat premature, because shortly after the hue and cry a volley of criticisms of the study came from various highly reputable quarters and called the study’s findings into question.

So, in the immortal words of Marvin Gaye, what’s going on?

Let’s start with the Canadian study, which was funded by the Canadian Centre on Substance Use and Addiction and, by its own admission, was set up to find flaws in other alcohol studies.

This fault-finding exercise involved a desk-based review of 107 published and peer-reviewed studies on alcohol consumption. These were all recent additions to an extensive field of research that stretches back decades and which has resulted in the well-established science around the potential benefits of moderate drinking – science that underpins alcohol guidelines in countries around the world such as ours.

Here in New Zealand, the Ministry of Health guidelines for safe drinking are two standard drinks a day for women, and three standard drinks a day for men, with at least two alcohol-free days each week.

These guidelines reflect the extensive research which indicates that moderate alcohol consumption, such as that suggested by our guidelines, does not negatively impact life span. Further, moderate alcohol consumption appears to have health benefits in relation to preventing cardiovascular disease and type 2 diabetes. For this reason, moderate drinkers (in general) have been found to live longer than abstainers.

These findings, confirmed by thousands of studies over the years, have led to the widespread endorsement of the existence of a “J-curve”, which represents the health risks associated with drinking falling with light or moderate consumption and then steadily rising in proportion to consumption of alcohol.

In other words, if we plot the lifespans of a population on a line across a horizontal axis, with those who don’t drink at all on the left, and those who drink more heavily to the right, there is a dip shortly after the beginning of the line which represents those who drink moderately because they live, on average, a little longer than non-drinkers. This is according to the vast majority of research which has been conducted now for decades.

It was this well-documented trend – the J-curve – that the Canadian research was looking to challenge.

And hey presto – after “moderating” the 107 studies claimed to find no evidence of the health benefits, even suggesting those who abstained from drinking enjoyed longer lifespans.

This is the kind of catchy headline material that appeals to news organisations because it claims to turn long-held science on its head. But the problem is that the catchy conclusion wasn’t supported by the findings.

Virginia Nicholls. Photo / Linda Robertson, Otago Daily Times, File

Members of the International Scientific Forum on Alcohol Research released a critique that showed the Canadian researchers were demonstrably biased in their approach, and pointed out that the data still showed a J-shaped relationship between alcohol consumption and all-cause mortality which was at odds with their claims.

British author Christopher Snowdon waded in, pointing out that the study ultimately relied on just a handful of the 107 studies it had reviewed to support its conclusion. He joined the abovementioned experts to decry the researchers’ subjectivity, accusing them of cherry-picking from hundreds of published papers to rely only on those that confirmed its bias – and then not very clearly.

It goes to show that sometimes nothing gets in the way of a good story, least of all the evidence. But if you enjoy the occasional alcoholic beverage responsibly and your consumption is within guidelines, you can still enjoy your drink knowing that you are not necessarily putting your health at risk and may even be lengthening your life a little in the process.

- Virginia Nicholls is the executive director of the NZ Alcohol Beverages Council.