I'm awfully fond of the advice to drink wine in moderation. It introduces us the non-intuitive understanding that many things in nature have an inverted U relationship: A little bit is good, adding some more doesn't improve outcome, but high levels of the same "healthy" substance make it toxic and not healthy at all. Vitamins behave this way, so does homework. Why, even too much honesty can turn you cruel.
So "some is good, more is not better" is a common principle of healthy lifestyle.
Many observational studies show that people who drink alcohol in moderation have lower rates of heart disease. Although there are plausible mechanisms that can explain why wine in moderation can be good for your heart -- antioxidants, effect on cholesterol etc. -- the question remains: Does wine improve health, or is moderate drinking what healthy people do? After all, moderate drinkers of wine do tend to be people who are in a certain socioeconomic group, and moderate wine drinking usually is accompanied by other healthy habits.
Is some better than none?
The classic way to get rid of this kind of bias is to randomly assign similar people to abstinence, light and heavier drinking, control for all else, and follow them for many decades, but since we can't do that, a new study found a clever way to look at the issue in a new way. The study, published in the British Medical Journal included 260,000 people, and used genetic randomization. Most genes are passed on from parents to children randomly, and in the case of alcohol there is a gene variant that is associated with lighter drinking. The variant is in the alcohol dehydrogenase 1B gene, and people who inherit it tend to drink less because their alcohol breakdown enzyme works faster, and they feel alcohol's unpleasant side effects -- such as nausea, headache and flushing -- more readily. This, in effect, randomizes society by genes, and not by socioeconomic influences.
And indeed the people with this gene variant in the study tended to drink less: They drank 17 percent fewer drinks per week, had fewer incidences of binge drinking, and many more of them abstained altogether. There still was a wide variation in drinking among people with the variant, supporting the notion that there are societal influences and drinking culture affects on drinking behavior -- even among people with a genetic predisposition to drink less.
So if a whole subset of the population is randomly assigned by their genetic makeup to drink less, and alcohol in moderation causes better heart health, we'd expect the people with the alcohol dehydrogenase 1B gene variant to show both above average and below average cardiac outcomes: those of them with the lowest consumption should have slightly worse cardiac outcomes.
This is not what the researchers found. Quite the contrary: Those with the gene had 10 percent less coronary heart disease, as well as lower blood pressure, lower BMI, and lower "bad" cholesterol levels across the board. And the researchers conclusion:
These findings suggest that reductions of alcohol consumption, even for light to moderate drinkers, may be beneficial for cardiovascular health. Our results therefore challenge the concept of a cardioprotective effect associated with light to moderate alcohol consumption reported in observational studies and suggest that this effect may have been due to residual confounding or selection bias.
Skip the glass of wine?
What to do with this information? I just read it with interest. I do suggest you take a peek at the paper, and see the list of authors -- two pages long -- and the list of participating institutions -- a page and a half of tiny print long. If you enjoy your daily glass of wine I wouldn't worry about the contradictory findings. On the other hand, if anyone ever suggested you start drinking alcohol for your health, I'd say that advice isn't yet established.
The fact that it's taking so long and so much to get a clear answer suggests that the effects of alcohol in moderation for better or worse heath are relatively minor.