Australian-led research claiming moderate alcohol intake is associated with a reduced risk of heart disease and death is not based on strong evidence, and fails to take into account recent research findings linking even moderate alcohol intake to cancer, experts say.
A research letter from Monash University reported the results of a survey of 18,000 people in the US and Australia over the age of 70 who were asked about their alcohol consumption.
The researchers followed the participants for almost five years and found a reduced risk of cardiovascular disease in people who consumed between more than five standard drinks a week compared to those who never drank, regardless of gender.
They found consuming five to 10 standard drinks a week was associated with a reduced risk of mortality from all causes. The findings were published in the European Journal of Preventive Cardiology.
Associate Prof Andy Towers, an addiction researcher from the school of health sciences at Massey University in New Zealand, said there had been numerous studies over the years showing an association between moderate drinking and reduced mortality. But the findings of many of those studies had since been called into question with problems in their methodology.
The Monash University study used similarly outdated methods that did not account for the socioeconomic status of participants, Towers argued. Higher socioeconomic status is known to be protective against poor health. Selection bias of participants – which meant they were generally more healthy to begin with – and the limitations of observational studies where participants self-report alcohol intake have been found to artificially show an association between drinking and better health.
On a graph, this association looks like a j-shaped curve, with the lowest point on the curve – light-to-moderate drinking – representing the “ideal” level of exposure to alcohol to offer health benefits.
“This sort of analysis has often been cited as a reason to support moderate drinking as being beneficial for health,” Towers said.
“[But] in our own research, we’ve tried to explain why you cannot make claims about the health benefits of alcohol with exactly this type of graph. We show that this is clearly not a causal relationship and is actually reflective of someone’s socioeconomic status. We show that once you control for how rich or poor someone is the relationship between alcohol and health no longer exists.”
The research letter notes this as a limitation of the study, acknowledging there was “a potential healthy volunteer bias due to the selection process of a clinical trial” and that socioeconomic factors were “unmeasured or underestimated”.
Towers said generally people who drink moderately are also people “who are richer, have better houses, have better jobs, have better education and can – as a result – afford better lifestyles that support better health”.
“Basically, saying that moderate drinking causes better health is just as nonsensical as saying that having a Ferrari causes better health. It’s not the drinking causing better health – both health and the tendency to drink moderate amounts are reflective of middle-class lifestyles.”
The research letter cites just five other research papers and does not include references to recent papers linking even modest alcohol intake to cancer. The researchers were monitoring the health impact of aspirin intake in healthy older people. They asked the same study participants about their alcohol intake to draw their findings.
Towers said he was concerned the public would be left confused and misinformed as a result of the research letter. Media have widely reported on the study.
“The intent of these authors was likely positive and to explore an issue of significant interest to the public,” Towers said. “However, it ignores best-practice and some of the hard-won insights we’ve gained in alcohol research over the past decade.”
The Heart Foundation’s position statement on alcohol recommends that to reduce the risk of harm from alcohol-related disease or injury, healthy men and women drink no more than 10 standard drinks a week and no more than four standard drinks on any one day. The previous weekly guideline was 14 standard drinks a week but that was reduced to reflect the latest evidence.
The Heart Foundation’s manager of clinical evidence and gerontologist, Dr Amanda Buttery, said an observational study “cannot establish a direct cause of the impacts of alcohol on heart health in people aged 70 years and older”.
Buttery said the Heart Foundation recently reviewed the best evidence relating to alcohol and cardiovascular health. The evidence reviewed “presents a clear picture of the harms of alcohol consumption,” Buttery said.
“Alcohol is not a necessary or recommended part of a heart-healthy diet. It contributes unnecessary kilojoules and is of low nutritional value. Alcohol can also have negative impacts on blood pressure, heart rhythm and inflammation.
“The relationship between alcohol and health is becoming clearer. There is strong evidence that consuming alcohol increases the risk of various cancers including mouth, pharynx, larynx, some oesophageal, breast, colorectal, stomach and liver cancers. It can seriously impact on your heart health too, by increasing the risk of heart rhythm disorders like atrial fibrillation, which can lead to stroke.”
Buttery noted that people who had a previous heart attack or stroke were excluded from the Monash University study which might have affected the findings.
“There is not strong enough evidence to recommend a safe level of drinking for cardiovascular health,” Buttery said.
