Contrary to decades of studies suggesting moderate drinking is better than not drinking at all – and could even promote longevity – recent analysis of more than 40 years of research has concluded that many of those studies were flawed and that the opposite is true.
No amount of booze is good for you, concluded a team of Canadian researchers.
Their review found that the risks of dying prematurely increase significantly for women once they drink 25 grams of alcohol a day, while risks to men increase significantly at 45 grams of alcohol a day, or slightly more than three drinks.
The New York Times notes that the report, which analysed more than 100 studies of almost 5m adults, was not designed to develop drinking recommendations, but to correct for methodological problems that plagued many of the older observational studies. Those reports consistently found that moderate drinkers were less likely to die of all causes, including those not related to alcohol consumption.
Most of those studies were observational, meaning they could identify links or associations but they could be misleading and did not prove cause and effect.
Scientists said that the older studies failed to recognise that light and moderate drinkers had myriad other healthy habits and advantages, and that the abstainers used as a comparison group often included former drinkers who had quit alcohol after developing health problems.
“When you compare this unhealthy group with those who go on drinking, it makes the current drinkers look healthier – as if they have lower mortality,” said Tim Stockwell, a scientist with the Canadian Institute for Substance Use Research and one of the authors of the new report, which was published in JAMA Network Open.
Once he and his colleagues had corrected for these errors and others, he said, “the supposed health benefits of drinking shrink dramatically, and become non-statistically significant”.
The comparisons of moderate drinkers with non-drinkers were flawed for numerous reasons, he added. People who abstain completely from alcohol are a minority, and those who aren’t teetotallers for religious reasons are more likely to have chronic health problems, to have a disability, or to be from lower income backgrounds.
Moderate drinkers tend to be moderate in all ways, tending to be be wealthier, more likely to exercise and to eat a healthy diet, and less likely to be overweight. They even have better teeth, scientists say.
“They have many things going for them that protect their health, and that have nothing to do with their alcohol use,” Stockwell said.
The idea that moderate drinking may be beneficial dates back to 1924, when a Johns Hopkins biologist named Raymond Pearl published a graph with a J-shaped curve, the low point in the middle representing the moderate drinkers, who had the lowest rates of mortality from all causes.
The high point in the J represented the well-known risks of heavy alcohol consumption, such as liver disease and car crashes. The hook on the left represented abstainers.
In more recent decades, wine — and particularly red wine — has developed a reputation for having health benefits after article highlighting its high concentration of a protective antioxidant called resveratrol, which is also found in blueberries and cranberries.
But the moderate alcohol hypothesis has come under increasing criticism over the years as the alcohol industry’s role in funding research has come to light, and newer studies have found that even moderate consumption — including of red wine — might contribute to cancers of the breast, oesophagus and head and neck, high blood pressure and atrial fibrillation.
In January, Canada issued new guidelines warning that no amount of alcohol is healthy, urging people to reduce their drinking as much as possible. Issued by the country’s Centre on Substance Use and Addiction, it was a stark departure from its 2011 guidelines, which recommended women limit themselves to no more than 10 standard drinks a week and men no more than 15.
Now the Canadian agency says that even two standard drinks a week is associated with health risks, and seven or more weekly drinks carry a high level of risk.
Current US dietary guidelines are less strict, recommending men limit themselves to two drinks or less a day and women to one or less.
But guidelines about alcohol consumption issued by numerous health organisations have been amended to include the proviso that people should not drink alcohol for the express purpose of improving their health.
That caveat was repeated by a scientist with the Distilled Spirits Council, though she took issue with the findings of the new report.
Amanda Berger, vice president for science and health with the Distilled Spirits Council, said the new analysis still “suggests that those who moderately live longer than those who do not”, but added, “no one should drink alcohol to obtain potential health benefits and some people should not drink at all”.
The new analysis shows, however, that those who drink moderately have no statistically significant advantage in longevity compared with those who are lifelong abstainers, the study’s authors said.
Study details
Association Between Daily Alcohol Intake and Risk of All-Cause MortalityA Systematic Review and Meta-analyses
Jinhui Zhao, Tim Stockwell, Tim Naimi, et al.
Published in JAMA Network Open on 31 March 2023
Key Points
Question What is the association between mean daily alcohol intake and all-cause mortality?
Findings This systematic review and meta-analysis of 107 cohort studies involving more than 4.8m participants found no significant reductions in risk of all-cause mortality for drinkers who drank less than 25 g of ethanol per day (about two Canadian standard drinks compared with lifetime non-drinkers) after adjustment for key study characteristics such as median age and sex of study cohorts. There was a significantly increased risk of all-cause mortality among female drinkers who drank 25 or more grams per day and among male drinkers who drank 45 or more grams per day.
Meaning Low-volume alcohol drinking was not associated with protection against death from all causes.
Abstract
Importance
A previous meta-analysis of the association between alcohol use and all-cause mortality found no statistically significant reductions in mortality risk at low levels of consumption compared with lifetime non-drinkers. However, the risk estimates may have been affected by the number and quality of studies then available, especially those for women and younger cohorts.
Objective
To investigate the association between alcohol use and all-cause mortality, and how sources of bias may change results.
Data Sources
A systematic search of PubMed and Web of Science was performed to identify studies published between January 1980 and July 2021.
Study Selection
Cohort studies were identified by systematic review to facilitate comparisons of studies with and without some degree of controls for biases affecting distinctions between abstainers and drinkers. The review identified 107 studies of alcohol use and all-cause mortality published from 1980 to July 2021.
Data Extraction and Synthesis
Mixed linear regression models were used to model relative risks, first pooled for all studies and then stratified by cohort median age (<56 vs ≥56 years) and sex (male vs female). Data were analysed from September 2021 to August 2022.
Main Outcomes and Measures
Relative risk estimates for the association between mean daily alcohol intake and all-cause mortality. Results There were 724 risk estimates of all-cause mortality due to alcohol intake from the 107 cohort studies (4 838 825 participants and 425 564 deaths available) for the analysis. In models adjusting for potential confounding effects of sampling variation, former drinker bias, and other prespecified study-level quality criteria, the meta-analysis of all 107 included studies found no significantly reduced risk of all-cause mortality among occasional (>0 to <1.3 g of ethanol per day; relative risk [RR], 0.96; 95% CI, 0.86-1.06; P = .41) or low-volume drinkers (1.3-24.0 g per day; RR, 0.93; P = .07) compared with lifetime non-drinkers. In the fully adjusted model, there was a non-significantly increased risk of all-cause mortality among drinkers who drank 25 to 44 g per day (RR, 1.05; P = .28) and significantly increased risk for drinkers who drank 45 to 64 and 65 or more grams per day (RR, 1.19 and 1.35; P < .001). There were significantly larger risks of mortality among female drinkers compared with female lifetime non-drinkers (RR, 1.22; P = .03).
Conclusions and relevance
In this updated systematic review and meta-analysis, daily low or moderate alcohol intake was not significantly associated with all-cause mortality risk, while increased risk was evident at higher consumption levels, starting at lower levels for women than men.
See more from MedicalBrief archives:
Mixed reaction to Canada’s new two drinks a week only guideline
Moderate alcohol use can be good for the heart if rich, fatal if poor
No amount of alcohol is good for the heart – World Heart Federation
Red wine fights fat and improves memory