Experts agree that high alcohol consumption is harmful to your health. However, according to a popular page on alcohol from the Department of Nutrition at the Harvard School of Public Health, more than a hundred studies have shown that the risk of cardiovascular disease is slightly higher in people who do not do not drink at all compared to those who drink “in moderation”. On a graph, this translates into a “J” curve, it was explained in 2023 on the website of the Montreal Heart Institute: the risk would decrease when we stick to a few drinks per week, but would increase quickly when consumption increases.
Uncertain profits
These benefits of alcohol for the heart have, however, been called into question in recent years, noted for example, in 2022, an article published by the World Heart Federation – an organization dedicated to the fight against heart disease and stroke. cerebral.
Indeed, some studies were unable to observe the famous J-curve, particularly among black (2015) and Chinese (2008) participants. In its report published in 2023, the Canadian Center on Substance Use and Addiction (CCSA) also mentions that its analysis did not confirm the existence of such a J-shaped curve. Their report had ‘elsewhere caused a lot of debate (see this article by our colleague Jean-François Cliche).
Biased studies?
Most of what is known about the effects of alcohol comes from observational studies, which means that in many cases they do not take into account other factors that could confound the results, as noted in 2023 the CCDUS. However, alcohol consumption often comes hand in hand with other behaviors that can impact heart health.
For example, according to an American study in 2022, people who drink moderately have better lifestyle habits than those who abstain: less smoking, lower body mass index, more physically active, greater consumption of vegetables. A systematic review published the same year by another team of American researchers reported that wine drinkers had a better diet than beer or spirits drinkers.
Furthermore, people may have cultural, religious or medical reasons not to drink, the World Heart Foundation noted in 2022. A good analysis must therefore consider such factors.
Abstainers or former drinkers?
Another criticism of alcohol studies is that the abstainer group often includes former heavy drinkers who have reduced or stopped their drinking. This was the case for 86 studies out of the 107 analyzed in 2023 by Canadian researchers associated with the CCSA. However, these people may have changed their habits for health reasons, the authors wrote in a commentary published in 2024. This poor state of health of a high proportion of non-drinkers could explain why people who do not drink at all have more heart problems than moderate drinkers.
In their 2023 paper, the Canadian scientists analyzed 107 observational studies and adjusted their calculations to account for bias and confounding factors. They then observed no protective effect of alcohol. In other words, observational studies may overestimate the benefits of alcohol. This is also what American researchers concluded in 2022 in their systematic review.
Studies selected on dubious grounds
Since studies do not agree, the criteria for selecting them in a meta-analysis (i.e., a synthesis of studies) could influence the recommendations made to the public. For example, in another text published in 2024, Canadian researchers asserted that several guidelines are based on biased data. According to them, the International Scientific Forum on Alcohol Research, an organization which presents itself as a group of experts seeking to produce balanced analyses, applauds studies concluding the benefits of alcohol, but harshly criticizes those which show skepticism . They also criticize him for simply listing studies without mentioning their biases.
That said, the same criticism was leveled at the CCSA report. For example, the Heart Institute criticized the authors for choosing, in their meta-analysis, only 16 studies out of more than 5,000 available. The Canadian researchers were also criticized for bias in the selection of the 107 long-term follow-up studies that they then analyzed. They defend their decision by specifying that the studies included were those which contained the least bias.
(Archives AFP, BERTRAND GUAY/Archives AFP, BERTRAND GUAY)
Industry-funded studies
The World Heart Federation also highlighted, in 2022, that several studies on alcohol were obviously financed by the industry. For example, in 2018, the MACH study (Moderate Alcohol and Cardiovascular Health), established to study the beneficial effects of alcohol on the heart, was halted when the US National Institutes of Health (NIH) confirmed that two-thirds of the funding came from industry. In a review addressed to the journal of the American Public Health Association in 2020, British researchers revealed that MACH researchers had even approached alcohol producers by assuring them that their goal was to demonstrate the famous J-curve.
A simple consultation of the conflict of interest declaration of the International Scientific Forum on Alcohol Research (ISFAR) reveals that its members receive funding from the Australian wine industry, Brasseurs d’Europe and the Academy Dutch oenologists.
According to last October’s survey of Dutythe authors of the CCUS report were also accused of conflicts of interest by ISFAR, which accused them of their links with Movendi International, a movement advocating an alcohol-free lifestyle. However, journalists reported, a conflict of interest monitoring committee found nothing of concern.
Verdict
Several factors can influence the results of studies on the beneficial effects of alcohol on the heart, and several studies have failed to take these factors into account. Research therefore does not reach a consensus for the moment, but doubts about a beneficial effect require caution.
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