Souvenir from Dahab, 2009. Never had the courage to touch the contents.
Is alcohol healthy when consumed in moderate amounts?
The topic is controversial. Observational studies have found light to moderate drinking to be associated with less cardiovascular illness, but a recent research article in BMJ tips the scale in favor of ”probably not”.
In many previous studies, alcohol consumption and mortality have appeared to have a ”J”-shaped relationship: while heavy drinkers have a high risk of cardiovascular illness and mortality, light and moderate drinkers seem to enjoy smaller risk than teetotals (see e.g. these two much-quoted papers, and a more recent meta-analysis).
(The definition of moderate drinking, in case you were wondering, depends on who wrote the recommendations but generally means something like 1 or 2 drinks a day. Contrary to popular belief, red wine has not been proven superior to beer or spirits; in the studies mentioned above, only the amount of pure alcohol had significance.)
The way the J-shaped curve has traditionally been interpreted is that moderate alcohol consumption would prevent cardiovascular illness and prolong one’s life span. Biological mechanisms for how this might take place have also been proposed (see e.g. here).
But in the end it’s a correlation-causation thing: we only know there seems to be a connection but cannot tell if one really causes the other. (For entertaining examples of bizarre correlations, see here – movie appearances by Nicolas Cage vs. drowning deaths is my favorite.) Maybe the teetotals are abstinent because their underlying illnesses keep them from drinking alcohol? Maybe the people with “civilized” drinking patterns also have higher education, better incomes and more healthy behavior in general? The only way to find out for sure would be to run a randomized controlled trial, and this is unlikely to ever happen.
What the BMJ authors Holmes and Dale (and a lengthy list of collaborators) did was to look at a gene (a particular allele of alcohol dehydrogenase) that is known to be associated with lower alcohol consumption. While not a substitute for a clinical trial, this is quite a smart method really: gene alleles are randomly assigned to individuals (kind of), people cannot falsify them (like they might downplay their actual consumption of alcohol) and cannot be changed by lifestyle (so there is no possibility of the causation working two ways).
From the U shaped association seen in observational studies, we would expect that for drinkers below the nadir (12-25 units/week), a reduction of 17.2% in alcohol consumption — would lead to a small increase in the risk of coronary heart disease — Contrary to these expectations, however, we found that individuals below the nadir with a genetic predisposition to consume less alcohol had lower odds of developing coronary heart disease at all categories of alcohol consumption — bringing the hypothesised cardioprotective effect of alcohol into question.
So is moderate drinking healthy or not? The only really accurate answer at present is, we still don’t know. The new BMJ paper does not present definite evidence of alcohol’s causal effect because it uses a gene as a proxy and there may be confounding factors. However, it gets closer to proving causation than the older ”J-curve” studies.
The new study is welcome because it challenges the popular (but scientifically poorly founded) belief that moderate drinking is good for you. We need more info. The health effect of moderate drinking – be it positive or negative – may not be big from individual point of view – but given the very large alcohol-consuming population of the world, knowing the true answer to the question would have great importance to health policy.
Meanwhile, there is a lot we do know about the health effects of too much booze (it remains among the three leading risk factors for death and disability worldwide) and the practical advice regarding drinking stays largely the same.
If you’re an abstainer, there is no reason to start drinking because 1) there is no real proof that alcohol is beneficial; 2) even if it were, the gains would most likely be small, plus 3) you would risk drifting into the “heavy drinker” sector, which is unambiguously harmful. If you’re a moderate drinker, that’s probably OK; what the new BMJ paper hints, though, is that you might still be better off consuming less. I find it credible.