Most of us have been warned at one point in our lifetime that drinking brings health risks. But more recent observational studies have led to claims that drinking alcohol in moderate amounts can be beneficial. In men and women of middle age and older, studies have found a reduction in coronary heart disease (CHD) and ischemic stroke incidence.1,2
There does seem to be a threshold level up to which alcohol can reduce cardiovascular mortality. A recent meta-analysis of 19 cohort studies found a J-shaped association between drinking and CHD development. The lowest risk was found in people who consumed 1 or 2 drinks a day.
In other words, the risk can be reduced with a low-to-moderate daily intake, but the benefits disappear with heavier drinking.3,4,5
Protective effects of alcohol have been shown in:
The precise mechanism of alcohol’s positive effect hasn’t yet been defined, but one theory suggests that about half of the protection is attributed to increased high density lipid cholesterol (HDL-C) levels.1,2,4 Some small clinical trials have shown increased HDL-C with moderate alcohol consumption.2,5 HDL is of course the “good” cholesterol, helpful in transporting cholesterol from arterial walls to the liver, thereby reducing the chances of atherosclerosis development.2
There are other mechanisms that could explain alcohol’s protective effects in CHD. Some studies point to blood clotting effects, either through mitigation of platelet levels and coagulation factors (such as fibrinogen), or by directly improving the process of fibrinolysis by which the body breaks down clots.3 In vitro studies have found that alcohol’s inhibitory effect on prostaglandin synthesis decreases platelet aggregation.6 All these effects would tend to reduce clotting.
Despite this appealing observation, light-to-moderate alcohol consumption won’t necessarily be beneficial to everyone who seeks cardioprotection. Some people should not be drinking at all. This includes those who’ve previously been diagnosed with hypertriglyceridemia, pancreatitis, liver disease, hypertension, atrial fibrillation or congestive heart failure.2,5 Pregnant women shouldn’t drink any alcohol. For that matter, an association has been shown between consuming more than 0.5 drinks/day and female breast cancer.
Pinpointing the cause
Evidence gathered by Arthur Klatsky and the Kaiser Permanente Team Medical Care Program in Oakland, California, suggests that ethanol itself is the source of cardioprotection. Their 120,000-participant study revealed no difference between specific types of alcoholic beverage in measured CHD outcomes.2,5 This finding is consistent with a report released earlier by Harvard, though it goes against the popular wisdom, which holds that red wine is especially helpful. It’s true that red wine and beer contain antioxidants not found in other alcoholic drinks, but conclusive comparisons have proved impossible to make, since few people confine themselves to one type of drink. In any case, on this question, the quantity of alcohol is surely more important than the quality.3
Excessive drinking (more than 3 drinks a day) is well known for being toxic to the heart and dangerous to health in general. The body digests ethanol through a series of reduction-oxidation reactions. The by-products of this process place tremendous oxidative stress on the body and can lead to various problems, including inhibition of DNA repair, uric acidosis and ketosis. Ethanol can also influence the heart’s rhythmic beating patterns and increase the risk of dysrhythmias such as ventricular tachycardia.2 Heavy alcohol consumption increases the risk of developing other diseases and complications such as liver cirrhosis, breast and gastrointestinal cancer, pancreatitis, alcoholic cardiomyopathy, hypertension, addiction, accidents, suicides and homicides.2,3
This isn’t a question that’s been thoroughly explored with randomized controlled trials.1,2,4 Many of the existing findings come from short-term observational studies, which may be influenced by lifestyle, diet and cultural factors.5 Even a broken clock is right twice a day, and evidence can be sought to support any observation. The sheer quantity of evidence, however, is becoming hard to ignore. Much of it indicates that one or two drinks per day can benefit your heart.
More controlled, long-term studies are needed to evaluate the true potential benefits and drawbacks of alcohol consumption. The American Heart Association’s nutrition committee has estimated that alcohol consumption in the U.S. prevents 80,000 cardiac deaths each year, mostly in people 45 years or older who have controlled blood pressure and are at risk for cardiovascular disease. These individuals are also characterized by their fitness and low HDL-cholesterol levels. On the other hand, 100,000 non-cardiac deaths are attributed to alcohol in younger age groups.2
The majority who know how to drink sensibly can draw comfort this Christmas from what we do know — that the odd tipple is unlikely to do much more harm than good. That doesn’t mean one should take up a daily routine of drinking for the sake of one’s health, but it does mean one may drink moderately for pleasure, and not feel guilty about it.
Gregory P. Curnew, MD, FRCPC is Associate Professor at McMaster University in Hamilton, ON, and Director of the Coronary Care Unit at Hamilton General Hospital.
Jeffrey Lee is a Bachelor of Health Sciences at McMaster University.