Just how risky is it to drink more alcohol than Canada's new guide advises?

When newly revamped guidelines for low-risk alcohol use were revealed last week, it quickly sparked debate and, in some cases, frustration. Some Canadians were quick to dismiss them, saying the risks felt overblown.

The guidelines, released last Tuesday by the Canadian Centre on Substance Use and Addiction (CCSA), state that no amount of alcohol is safe and recommends no more than two drinks a week for men and women, as alcohol-related deaths soar in Canada.

"My initial impression was, 'You've gotta be kidding!'" said Dan Malleck, a professor of health sciences at Brock University in St. Catharines, Ont., and an internationally recognized historian of alcohol and drug policy.

He suggested that the way the CCSA presented alcohol-cancer risks was overblown, adding that the lack of comparative risks made it difficult for people to absorb. "It was suggesting that somehow we can avoid death," he said.

Other Canadians called for clearer risk comparisons, saying they would like to understand just how dangerous it is to ingest more than the recommended number of glasses per week — and ultimately decide for themselves.

"If it increases an already-low chance of a cancer, by 0.5, or one, or even five per cent, it would take thousands of cases to have any real significance. I believe that this is vital information to enable people to make informed choices," said Bob Burns, a retired doctor from Nanaimo, B.C., who was one of dozens of people who wrote to CBC News to comment after the guide was publicized.

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Burns, who has had breast cancer, wanted to know exactly how much alcohol contributes to each type of cancer. But the authors of the new guidelines say it's scientifically tricky to compare the cancer risks of a few extra shots of tequila to other life-threatening activities.

"It is good that people are grappling with the numbers," said Peter Butt, an associate professor at the College of Medicine at the University of Saskatchewan, and co-chair of Canada's Guidance on Alcohol and Health.

"There is no safe level, so less is always better."

What's an acceptable risk?

The CCSA authors point to a 2019 U.K study that compares the cancer risks of alcohol and tobacco. They say while it's not widely cited, and a bit problematic, due to the more addictive nature of tobacco, it's still an interesting comparison.

That study found that a standard drink is equivalent and comparable to one cigarette for men and two cigarettes for women. The summary explains that one bottle of wine per week is associated with an increase in lifetime cancer risk — the same as five cigarettes a week for men, or 10 for women.

But Malleck says there's nothing that clear in the new moderate alcohol-use guidelines, arguing cancer is being used as a scare tactic. He said the authors of the guidelines showed no evidence of a "radical" risk of cancer, except for people with oral cancers, liver diseases and a few other conditions, creating undue stress in the public.

"If you're creating anxiety and worry in people, you're not really doing anyone any favours, because we know that anxiety and worry have … negative physical health effects," said Malleck.

Butt explained that there are scientific parameters for calculating what is an acceptable risk.

These are based on a set of internationally accepted "mortality risk" standards, he said. For alcohol, people appear willing to accept a higher risk of death associated with consumption as compared with other voluntary activities, Butt said.

In the report on the new guidelines, risk is broken down by the number of drinks per week and specific diseases. It outlines exactly how many years of life — averaged over the lives of 1,000 males and 1,000 females — would be lost, depending on how many drinks they ingested per week and what disease they had.

It is not uncommon for countries — such as Australia, France or the U.K. — to base their alcohol guideline recommendations on a one in 100 mortality risk limit.

The new guidelines determined that in Canada, the limit that aligned with a one in 1,000 chance of premature death related to an alcohol was two standard drinks per week, while the one in 100 risk limit is six standard drinks per week.

"The numbers are sobering when we parse them out this way, but that is the evidence," Butt wrote to CBC in an email.

To determine the risks related to alcohol and cancer, Butt said, they relied on systematic reviews of research of 200 conditions causally associated with alcohol. The research used "robust population health data that must pass an internationally recognized grade analysis and causation proven in animal studies with cellular DNA.

'This isn't going to resonate'

What might have been more helpful is if the guide offered strategies to help individuals assess their personal risks, based on family health history or alcohol-use patterns, said Heidi Tworek, an associate professor of public policy at the University of British Columbia.

That way, she said, the guide could have been made a bit more accessible.

"There are a lot of people for whom this isn't going to resonate or they're never going to hear about it in the first place," said Tworek, a Canada Research Chair in health communication.

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As for complaints the new guidelines ignore alcohol's benefits, experts say Canada has been ignoring the real costs of over-consumption of alcohol for too long.

"Red wine is not good for your heart. Red wine increases your blood pressure. Alcohol, as a rule, just makes you gain weight. There is so much sugar in it. There is a reason we call it a beer belly not celery belly," Montreal cardiologist Christopher Labos told CBC News Network this week.

Some research suggests alcohol can negatively affect mental health conditions or increase the risk of cognitive problems and dementia. And alcohol overuse can interfere with vitamin absorption and sugar processing, leading to memory, movement, vision and co-ordination loss.

"I think that people would be very ill advised if they think there's 'nothing' wrong with alcohol," said Malleck, noting problems like impaired driving and addiction.