Why Canada’s low-risk alcohol use guidelines have been slashed to six drinks per week

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New Canadian guidelines for reducing risks to health from alcohol use were released for public comment this week. Key messages include:

  • drinking less alcohol is better for health;
  • health risks escalate quickly above six standard drinks per week, especially for women;
  • do not exceed two drinks per day to minimize risks;
  • alcohol is a carcinogen;
  • alcohol containers should carry prominent health warnings.

You may be asking, who took it upon themselves to give this advice to the public and upon what basis? I am a scientist at the Canadian Institute for Substance Use Research and was a member of the panel that generated this advice. I have also advised or been a panelist on four previous guideline committees over the past 30 years including for Australia, the United Kingdom and Canada.

I try to explain here some of the underlying science and how it has evolved, principally why drinking guidelines internationally have lowered definitions of “low-risk” alcohol use.

Why have the guidelines changed?

The new guideline development was led by the Ottawa-based Canadian Center on Substance Use and Addiction (CCSA) with funding from Health Canada. The previous 2011 guidelines were far more generous: low-risk drinking was defined as up to 10 standard drinks per week for women and 15 for men.

A standard drink is a mystery to many people, not least because unlike in some other countries (e.g. Australia and New Zealand) alcohol containers here do not state how many standard drinks they contain. In Canada, a standard drink is defined as 13.45 grams of ethanol, which corresponds to typical serve sizes of average strength beer, wine and spirits:

  • 341 milliliters of beer or cider (5% alcohol),
  • 142 milliliters of wine (12% alcohol) or
  • 43 milliliters of spirits (40% alcohol.

What has changed in the past 11 years? Why is an expert committee now recommending much lower guidelines? I was also a member of the panel for the 2011 guidelines, which were based upon the simple idea that low-risk drinking was a level that didn’t increase health risks above that of an abstainer.

Criticism of the old guidelines

In compiling the 2011 guidelines, we looked at comprehensive reviews of the link between alcohol use and risk of premature death. These almost invariably showed that light and moderate drinkers had less risk than abstainers but, above a break-even point, health risks quickly escalated. Many observational studies have suggested low-volume drinkers are “protected” from heart disease, type II diabetes and some kinds of stroke. This evidence is now questioned.

Based on the best quality systematic review available at that time we noted that at two drinks per day for women and three for men, mortality risks were equal to those for abstainers. We recommended at least two days of abstinence a week ending up with the 2011 guideline of 10 drinks per week for women and 15 per week for men.

This approach has been criticized from many angles. Studies in such reviews are from all over the world, albeit with a North American and European bias, but estimates should be tailored more precisely for any specific country. Another criticism is that estimates of the association between level of alcohol use and death from all causes will be heavily confounded by other lifestyle factors.

A better approach, these critics argue, is to estimate risks from alcohol use for a select number of diseases and types of injury known to be caused by alcohol, such as liver disease, breast cancer, road crash injuries, etc.

When such an approach is used, this break-even point (the point at which potential benefits and risks cancel each other out) is at a much lower level than from the all-cause mortality studies. My colleagues and I recently estimated this would be at about one drink per day, even assuming some protection against heart disease.

Risk levels

With the net risk of alcohol-related harm increasing at even low levels of consumption, guideline committees in other countries (such as the U.K. and Australia) have resorted to defining an “acceptable” level of risk from alcohol.

For external risks such as from air pollution or radiation from a nuclear power reactor, acceptable risk is generally taken as being an increase in mortality risk of less than one in a million. If an equivalent risk for external factors was taken for alcohol, I calculate that would mean, on the basis of the new guideline risk estimates, never drinking more than one drink per year!

For personal behaviors such as sexual risk-taking, smoking and alcohol use, people are prepared to accept higher levels of risk, for example, up to one in 100.

New Canadian guidelines

The new Canadian guidelines followed strict procedures for making as impartial and up-to-date an estimate as possible. Committee members were public health, medical and epidemiology experts who had no financial interests in the manufacture or sale of alcohol.

An independent team used strictly defined search criteria to locate the latest high quality published studies on alcohol risks for health conditions specified by the World Health Organization’s Global Burden of Disease study group.

When these risk relationships were collected and applied to Canadian data on causes of death and life expectancy, it was estimated that lifetime mortality risk from alcohol was less than one in 100 for men and women consuming no more than six drinks per week. Risks were elevated even at two drinks per week, at a risk level just under one in 1,000.

These new guidelines are provided on the basis of the latest science, guided by the principle that citizens have a right to know potential health effects of products. This is especially true for products distributed and sold directly by Canadian governments in most provinces and territories.

Alcohol and heart health

The careful review process identified much weaker evidence than before for the hypothesis that low doses of alcohol can protect against heart disease. This finding is also consistent with a World Heart Federation statement released earlier this year, advising that the science underlying this hypothesis is now highly contested and, at best, extremely weak.

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