Studies showing that alcohol protects the heart raise questions about drinking.
Does moderate, prudent drinking protect the heart and arteries? Two analyses say — shout, actually — that the answer is yes. But they raise a bigger issue: What should we do with this information? The answer to that question may come as a surprise.
Let's look at the findings first. Researchers from the University of Calgary, University of Texas Health Science Center, and Harvard Medical School scoured the medical literature for long-term studies that compared drinking habits with the development of cardiovascular disease. Of the 4,235 studies they identified, 84 met the researchers' strict criteria. When combined, these studies included more than two million men and women who were followed for an average of 11 years.
Using a technique called meta-analysis, the researchers pooled results from the 84 publications and analyzed the data as if they were from one gigantic study. Compared with no alcohol use, moderate alcohol use (see "What is 'a drink'?") over the average study duration
reduced the risk of a new diagnosis of coronary artery disease by 29%
reduced the risk of dying from any cardiovascular disease by 25%
reduced the risk of dying from a heart attack or coronary artery disease by 25%
reduced the risk of dying from any cause by 13%
reduced the risk of having an ischemic (clot-caused) stroke by 8%
increased the risk of dying from a stroke by 6%
increased the risk of having a hemorrhagic (bleeding) stroke by 14%.
The amount of alcohol consumed influenced the effect. For coronary artery disease and death from it, any amount of alcohol — from just under one-half drink per day on up — reduced heart disease risk by about 25%. But this was offset by stroke risk: at four drinks per day, the risk of having a stroke was 62% higher than it was with no alcohol use, and the risk of dying from a stroke was 44% higher. The lowest risk for any cause of death was at one drink per day (BMJ, Feb. 26, 2011).
A companion article by the same authors summarized the strong evidence for how alcohol might influence cardiovascular disease — by boosting protective HDL and adiponectin (a hormone that has beneficial effects on blood sugar, the breakdown of fats in the bloodstream, and the inner lining of arteries), and reducing levels of fibrinogen (a protein that helps form blood clots). Wine, beer, and spirits appeared to have similar effects.
What is "a drink"?
In the United States, a standard drink contains about 0.6 fluid ounces of alcohol. The drinks shown above contain roughly that amount of alcohol. Moderate drinking is generally defined as no more than two drinks a day for men and no more than one drink a day for women. The National Institute on Alcohol Abuse and Alcoholism defines drinking as low risk, increased risk, and highest risk.
A case for limits
You might expect the authors of this work to conclude that drinking alcohol is good for the heart and arteries and might be recommended to some people. Instead, they concluded that "our findings lend further support for limits on alcohol consumption."
The researchers based this conclusion on the complexity of alcohol's effects on health. Moderate drinking offers some protection against coronary artery disease, but it does just the opposite for hemorrhagic stroke, while heavier drinking significantly increases the risk of having or dying from a stroke. And then there's the rest of the body to consider.
Alcohol's dark side
Alcohol affects every system in the body, from the brain on down. For people who aren't addicted to alcohol, a little bit has no long-lasting ill effects and may, in some instances, be beneficial, as with the heart and arteries. For example, a small amount of alcohol taken with a meal improves tissues' sensitivity to insulin, which may decrease the chances of developing type 2 diabetes.
Excessive consumption of alcohol is only harmful (see "Alcohol and health"). It is a major cause of preventable deaths and contributes to liver disease, a variety of cancers, and other health problems. Too much alcohol can dissolve the best intentions and the closest relationships.
"Few people know what so-called safe drinking is, and many have no idea of the harm alcohol can cause," says Dr. Kenneth J. Mukamal, an author of the two BMJ papers and an internist at Harvard-affiliated Beth Israel Deaconess Medical Center.
Alcohol and health
When it comes to health, alcohol is a sharp, double-edged sword. A little bit of alcohol, in the neighborhood of a drink a day, may be beneficial for the heart and arteries. With excessive drinking, which differs from person to person, the risks or hazards outweigh the benefits. The CDC estimates that excessive alcohol use contributes to almost 80,000 deaths a year in the United States. These come from motor vehicle accidents and violence, liver disease and hemorrhagic stroke, and 50 other causes.
Immediate health risks
Long-term health risks
For some people, having a glass of wine, a beer, or a cocktail is a pleasurable social or relaxing activity. For others, drinking alcohol leads to nothing but problems. There are more people in the latter category than we'd like to think.
A nationwide survey of 43,000 adults conducted by the National Institutes of Health tells a cautionary tale. Among those who said they drink alcohol, four in 10 were heavy drinkers or at risk for becoming one. To look at it another way, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) estimates that nearly 19 million Americans have a problem with alcohol.
Redefining alcohol consumption
The terms "moderate" and "excessive" have long been used to describe drinking habits. The NIAAA now uses more descriptive terms — low risk, increased risk, and highest risk. In this case, risk refers to the chances of developing alcohol-related health problems, alcoholism, or both.
Low-risk drinking. For men, this is no more than four drinks in a single day and no more than 14 drinks in a week; for women, no more than three drinks in a single day and no more than seven drinks in a week. (About 57% of Americans who drink alcohol fall into this category.)
Increased-risk drinking is drinking more than either the single-day limit or the weekly limit (29% of drinkers).
Highest-risk drinking is drinking more than the single-day limit and the weekly limit (14% of drinkers).
How much and how often you drink constitute one way to identify if you have a problem with alcohol. Other measures include the effect that drinking has on you and how you feel about it. These are included in three commonly used tests: the CAGE test, the World Health Organization's AUDIT, and a questionnaire from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). You can take all three of these tests at health.harvard.edu/173.
No prescription for alcohol
Studies supporting the cardiovascular benefits of drinking alcohol have often raised the question of whether some older people should start drinking, or if doctors should sometimes recommend it. "From a health perspective, there are few, if any, situations in which it makes sense for someone to begin drinking alcohol," says Dr. Mukamal. The potential benefit is limited (more exercise would be a better choice). It would take more time than most doctors can give to have a nuanced conversation about the risks and benefits of alcohol. And encouraging nondrinkers to begin drinking "doesn't make good medical sense, since there's no proof they can do it safely," Dr. Mukamal cautions.
If alcohol affected only the coronary arteries, drinking it might be good medicine. But it affects almost every other part of the body, and the amount consumed determines the ultimate outcome. That means a more careful approach to this two-faced beverage is in order.
For more information
Rethinking Drinking, a free report from the NIAAA, is another excellent resource. It is available online at rethinkingdrinking.niaaa.nih.gov.