These findings are yet another blow to the belief that drinking small amounts of alcohol can be good for our health.
“There are no protective effects of moderate alcohol intake against stroke,” said Zhengming Chen, one of the study’s authors and an epidemiologist at the University of Oxford, in a released statement. “Even moderate alcohol consumption increases the chances of having a stroke.”
As I’ve explained here before, the idea that having a beer or glass of wine each day provides a health benefit is primarily based on studies that have suggested alcohol’s relationship to mortality has a J-shaped curve: light to moderate drinkers (up to two drinks per day) have a lower risk of premature death (including from stroke and heart attack) than teetotalers, and then, as alcohol consumption increases, the risk of death also climbs.
But the scientific evidence for that idea — that moderate drinking is not only good for us, but better than abstaining — has always been weak because it fails to account for the possibility that many teetotalers may have stopped drinking alcohol because of existing medical problems. This new study shows just how weak those previous studies may have been.
A unique control group
For the study, Chen and his colleagues at the University of Oxford collaborated with researchers at Peking University and the Chinese Academy of Medical Sciences in Beijing, China. They analyzed 10 years of data collected from more than 500,000 men and women in China who were participants in a larger health-related research project. The participants lived in both urban and rural areas of China, and their mean age at the start of the study (between 2004 and 2008) was 52.
A third (33 percent) of the men and 2 percent of the women reported drinking at least some alcohol — mostly spirits — weekly. (As the study’s authors point out, due to cultural reasons, few women in China drink alcohol.)
The researchers focused their study on a Chinese population because many people of East Asian descent have a genetic variant that causes them to be intolerant to alcohol. When people with this variant have an alcoholic drink, they experience an extremely unpleasant flushing reaction.
The variant does not affect other factors that raise or lower the risk of stroke, such as diet, smoking, physical activity and socioeconomic status, so it provided a unique non-alcohol-consuming “control group” for the study. Of the 500,000 people followed in the current study, about 160,000 had this variant.
The participants’ health was followed for about 10 years, until the beginning of 2017. During that time, about 10,000 of the men had a stroke. When the researchers compared the rate of stroke in men based on their alcohol consumption, they found that consuming one to two alcoholic drinks per day increased the risk by 10 to 15 percent, while consuming the equivalent of four drinks a day increased the risk by 35 percent.
A drink in the study was the equivalent of a small glass of wine, a bottle of beer or a single measure of spirits (hard liquor).
The study found no evidence that consuming one or two alcoholic drinks daily had any protective effect.
Backing up those findings is the fact that the women in the study with the gene variant were not at lower risk of having a stroke than those without the variant — presumably because neither group drank alcohol.
Based on the study’s results, Chen and his colleagues estimate that alcohol is responsible for 8 percent of all ischemic strokes (ones caused by a blood clot in the brain) and 16 percent of all hemorrhagic strokes (ones caused by bleeding in the brain) in men in China.
The study also looked at the effect of alcohol consumption on heart attack risk, but only 2,000 of the men in the study had a heart attack, which is too small a number to make any finding statistically significant, the researchers say.
‘Too good to be true’
Despite its rather unique approach, the study is still observational, which means it can’t prove that alcohol was the direct cause of the higher risk of stroke observed among the drinkers in the study.
The study also relied on the participants self-reporting how much alcohol they drank, and such reports can be inaccurate.
Furthermore, most of the alcohol consumed by the study’s participants was hard liquor. The findings may or may not apply to the alcohol found in beer or wine.
Evidence from other research suggests they do, however. A study published last year in The Lancet, for example, found that no amount of wine, beer or hard liquor was safe for people’s overall health. And just last month, U.S. researchers reported that moderate alcohol consumption of any kind (seven to 13 drinks per week) substantially raised the risk of high blood pressure.
As Dr. Tim Chico, a cardiologist at the University of Sheffield who wasn’t involved in the study, told Guardian reporter Nicola Davis yesterday, alcohol’s impact on the risk of stroke will likely vary from individual to individual, based on each person’s underlying risk — their age, weight, and lifestyle factors such as smoking and exercise levels.
But that doesn’t mean that drinking alcohol is risk-free for anyone. Nor does it mean that consuming it is beneficial.
“Unfortunately, when something sounds too good to be true it usually is, and this study finds little evidence that alcohol is protective,” Chico added.
For more information: You’ll find the study on The Lancet’s website.