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To be at a low risk of suffering negative, acute and/or long-term health outcomes from drinking, the CCSA’s report says a person should consume, on average, zero to two standard drinks each week.

Drinking three beers a week increases your risk of developing breast or colon cancer, while sipping a daily glass of wine can make you more likely to develop heart disease and increases your chance of having a stroke, according to a new report highlighting the health risks of even moderate alcohol consumption.

The report, published on Monday by the Canadian Centre on Substance Use and Addiction (CCSA), examined several studies and said they show strong links between moderate-to-heavy alcohol use and some fatal illnesses, including cardiovascular disease and a number of cancers.

The centre, which advises Parliament on how to deal with addiction, also recommends mandatory labelling of alcoholic beverages that would indicate portion sizes for safe consumption.

“We are coming out with a recommendation where we are sharing with people in Canada a continuum of risk associated with different amounts of alcohol,” said Catherine Paradis, interim associate director of research at the CCSA. The report is open for public consultation until Sept. 23.

Dr. Paradis explained the suggested labeling is meant to show exactly how much alcohol is in any given drink.

Around the world, a standard drink is defined as a unit containing 8 to 20 grams of alcohol – that’s about half a shot to a shot and half of whisky. In Canada, a standard drink contains 13.45g of alcohol, which is the amount in a 30 millilitre shot of hard liquor, or a 354ml bottle of 5 per cent beer.

According to the CCSA’s report, to be at a low risk of suffering negative, acute and/or long-term health outcomes from drinking, a person should consume, on average, just zero to two standard drinks a week. As consumption goes up from there, so do the potential negative outcomes. Three to six drinks per week puts someone at a moderate risk of negative health outcomes. Six or more standard drinks per week puts a person at a high risk.

These numbers change slightly based on body weight and physiology. While men and women showed no overall difference in premature death, men are able to consume more drinks on average than women before suffering other serious health outcomes, including liver damage.

High-risk drinking among women also has a severe effect on reproductive health. Public-health experts have advised for decades against alcohol consumption during pregnancy because adverse effects of fetal exposure include brain injury, behavioural problems and learning disabilities. As well, recent research shows moderate- to high-risk alcohol consumption can affect a woman’s overall fertility and ovulation cycle, potentially complicating the ability to become pregnant.

“The whole philosophy behind this project is that people have a right to know and to make informed decisions,” said Dr. Paradis, who adds that the recommendations on labels are not intended to deter people from drinking.

“It was not so much for the label to work or not, but that if you want to count your drinks, you need to know how many drinks or how many standard drinks there are in a specific alcohol container.”

Some research highlighted in the report has shown that labels have a deterrent effect on high-risk drinking. A study from Whitehorse, Yukon, that surveyed more than 2,000 people who visited a single liquor store where alcohol products had labels for standard drinks and a cancer warning, found sales for the labelled alcohol dropped 6.6 per cent. Other studies have found that alcohol health labels led to a 10-per-cent increase in the ability to recall cancer risks and a 50-per-cent increase in being able to recall low-risk drinking guidelines among consumers.

Alcohol consumption in Canada is associated with steep health and economic costs. In 2017, according to the CCSA report, alcohol contributed to 18,000 deaths in Canada and that same year, $5.4-billion was spent on health care related to alcohol consumption.

Although the CCSA report examines the role of alcohol in issues such as intimate partner violence, one area Dr. Paradis said remains unresolved is how to address its relationship with mental health, which she said is poorly understood.

“Unfortunately, we were unable to find evidence that satisfied the very high quality criteria we set ourselves to use for this project,” Dr. Paradis said, noting that Australia faced a similar problem when reviewing its alcohol guidelines in 2016.

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According to a 2020 report from the National Health and Medical Research Council of Australia (NHRCA), a systematic review of research found “no reliable evidence” to support a causal relationship between alcohol consumption and almost every mental health issue, with “limited evidence of association” between alcohol consumption and worsening bipolar disorder.

Both the CCSA and the NHRCA said they gave poor grades to the state of research on the topic because most studies were limited in scope, difficult to interpret or relied on low-quality data collection. Dr. Paradis said some research would compare non-drinkers and drinkers, yet included former drinkers who were abstinent at the time of data collection in the category of non-drinkers, thus muddying the results.

“That’s definitely a next step for the scientific community, to continue to refine our methodologies and our studies on the association between alcohol and mental health, so that in the future, guidelines can also take into account this very important dimension,” Dr. Paradis said.

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