From the Harvard School of Public Health
Throughout the 10,000 or so years that humans have been drinking fermented beverages, they’ve also been arguing about their merits and demerits. The debate still simmers today, with a lively back-and-forth over whether alcohol is good for you or bad for you.
It’s safe to say that alcohol is both a tonic and a poison. The difference lies mostly in the dose. Moderate drinking seems to be good for the heart and circulatory system, and probably protects against type 2 diabetes and gallstones. Heavy drinking is a major cause of preventable death in most countries. In the U.S., alcohol is implicated in about half of fatal traffic accidents. (1) Heavy drinking can damage the liver and heart, harm an unborn child, increase the chances of developing breast and some other cancers, contribute to depression and violence, and interfere with relationships.
Alcohol’s two-faced nature shouldn’t come as a surprise. The active ingredient in alcoholic beverages, a simple molecule called ethanol, affects the body in many different ways. It directly influences the stomach, brain, heart, gallbladder, and liver. It affects levels of lipids (cholesterol and triglycerides) and insulin in the blood, as well as inflammation and coagulation. It also alters mood, concentration, and coordination.
What’s Moderate Alcohol Intake? What’s a Drink?
Loose use of the terms “moderate” and “a drink” has fueled some of the ongoing debate about alcohol’s impact on health.
Did You Know… The comparatively low rate of heart disease in France despite a diet that includes plenty of butter and cheese has become known as the French paradox.
Some experts have suggested that red wine makes the difference, but other research suggests that beverage choice appears to have little effect on cardiovascular benefit.
In some studies, the term “moderate drinking” refers to less than one drink per day, while in others it means three or four drinks per day. Exactly what constitutes “a drink” is also fairly fluid. In fact, even among alcohol researchers, there’s no universally accepted standard drink definition. (2)
In the U.S., one drink is usually considered to be 12 ounces of beer, 5 ounces of wine, or 1½ ounces of spirits (hard liquor such as gin or whiskey). (3) Each delivers about 12 to 14 grams of alcohol.
The definition of moderate drinking is something of a balancing act. Moderate drinking sits at the point at which the health benefits of alcohol clearly outweigh the risks.
The latest consensus places this point at no more than one to two drinks per day for men, and no more than one drink per day for women. This is the definition used by the U.S. Department of Agriculture and the Dietary Guidelines for Americans, (3) and is widely used in the United States.
Possible Health Benefits of Alcohol
What are some of the possible health benefits associated with moderate alcohol consumption?
More than 100 prospective studies show an inverse association between moderate drinking and risk of heart attack, ischemic (clot-caused) stroke, peripheral vascular disease, sudden cardiac death, and death from all cardiovascular causes. (4) The effect is fairly consistent, corresponding to a 25 percent to 40 percent reduction in risk.
Studies: Alcohol and Heart Disease
The connection between moderate drinking and lower risk of cardiovascular disease has been observed in men and women. It applies to people who do not apparently have heart disease, and also to those at high risk for having a heart attack or stroke or dying of cardiovascular disease, including those with type 2 diabetes, (5, 6) high blood pressure, (7, ) and existing cardiovascular disease. (7, ) The benefits also extend to older individuals. (9)
The idea that moderate drinking protects against cardiovascular disease makes sense biologically and scientifically. Moderate amounts of alcohol raise levels of high-density lipoprotein (HDL, or “good” cholesterol), (10) and higher HDL levels are associated with greater protection against heart disease. Moderate alcohol consumption has also been linked with beneficial changes ranging from better sensitivity to insulin to improvements in factors that influence blood clotting, such as tissue type plasminogen activator, fibrinogen, clotting factor VII, and von Willebrand factor. (10) Such changes would tend to prevent the formation of small blood clots that can block arteries in the heart, neck, and brain, the ultimate cause of many heart attacks and the most common kind of stroke.
Does Alcohol Cause These Benefits?
People who drink in moderation are different from non-drinkers or heavy drinkers in ways that could influence health and disease.
Folate and Alcohol
Folate, the B vitamin that helps guide the development of an embryo’s spinal cord, has equally important jobs later in life. One of the biggest is helping to build DNA, the molecule that carries the code of life. In this way, folate is essential for accurate cell division.
Alcohol blocks the absorption of folate and inactivates folate in the blood and tissues. It’s possible that this interaction may be how alcohol consumption increases the risk of breast, colon, and other cancers.
Getting extra folate may cancel out this alcohol-related increase. In the Nurses’ Health Study, for example, among women who consumed one alcoholic drink a day or more, those who had the highest levels of this B vitamin in their blood were 90% less likely to develop breast cancer than those who had the lowest levels of the B vitamin. (28) An earlier study suggested that getting 600 micrograms a day of folate could counteract the effect of moderate alcohol consumption on breast cancer risk. (26)
Part of a national 1985 health interview survey showed that moderate drinkers were more likely than non-drinkers or heavy drinkers to be at a healthy weight, to get seven to eight hours of sleep a night, and to exercise regularly. (11) Researchers have statistically accounted for such confounders, and they do not come close to accounting for the relationship between alcohol and heart disease. This, plus the clearly beneficial effects of alcohol on cardiovascular risk factors, makes a compelling case that alcohol itself, when used in moderation, reduces the risk of cardiovascular disease.
The most definitive way to investigate the effect of alcohol on cardiovascular disease would be with a large trial in which some volunteers were randomly assigned to have one or more alcoholic drinks a day and others had drinks that looked, tasted, and smelled like alcohol but were actually alcohol free. Many of these trials have been conducted for weeks, and in a few cases months, to look at changes in the blood, but a long-term trial to test experimentally the effects of alcohol on cardiovascular disease over many years will probably never be done. Nevertheless, the connection between moderate drinking and cardiovascular disease almost certainly represents a cause-and-effect relationship.
Beyond the Heart
The benefits of moderate drinking aren’t limited to the heart. In the Nurses’ Health Study, the Health Professionals Follow-up Study, and other studies, gallstones (12, 13) and type 2 diabetes (5, 14, 15) were less likely to occur in moderate drinkers than in non-drinkers. The emphasis here, as elsewhere, is on moderate drinking. In a meta-analysis of 15 original prospective cohort studies that followed 369,862 participants for an average of 12 years, no benefit was observed for heavy drinkers who consumed more than 48 grams of alcohol (the equivalent of four drinks) a day. (5) The social and psychological benefits of alcohol can’t be ignored. A drink before a meal can improve digestion or offer a soothing respite at the end of a stressful day; the occasional drink with friends can be a social tonic. These physical and psychic effects may contribute to health and well-being.
Drinking Patterns Matter
What you drink (beer or wine) doesn’t seem to be nearly as important as how you drink. Having seven drinks on a Saturday night and then not drinking the rest of the week isn’t at all the equivalent of having one drink a day. The weekly total may be the same, but the health implications aren’t. Among participants in the Health Professionals Follow-up Study, consumption of alcohol on at least three or four days a week was inversely associated with the risk for myocardial infarction. The amount consumed, under 10 grams a day or more than 30 grams, didn’t seem to matter as much as the regularity of consumption. (16) A similar pattern was seen in Danish men. (17)
The Dark Side of Alcohol
Spilled red wine If all drinkers limited themselves to a single drink a day, we probably wouldn’t need as many cardiologists, liver specialists, mental health professionals, and substance abuse counselors. But not everyone who likes to drink alcohol stops at just one. While most people drink in moderation, some don’t.
On the personal level, heavy drinking can take a toll on the body. It can cause inflammation of the liver (alcoholic hepatitis) and lead to scarring of the liver (cirrhosis), a potentially fatal disease. Heavy drinking can increase blood pressure and damage heart muscle (cardiomyopathy). It has also been linked with several cancers: In an exhaustive new report, the World Cancer Research Fund and American Institute for Cancer Research indicate that there is convincing evidence linking alcohol use to cancer of the mouth, pharynx, larynx, esophagus, breast, and colon and rectum in men, and probable evidence that its use contributes to liver cancer and colorectal cancer in women. (18) The risk is multiplied for drinkers who also smoke tobacco.
Problem drinking also touches drinkers’ families, friends, and communities. According to the National Institute on Alcohol Abuse and Alcoholism and others:
18.2 million Americans meet standard criteria for alcohol abuse or alcoholism. (19)
Alcohol plays a role in one in three cases of violent crime. (20)
More than 16,000 people die each year in automobile accidents in which alcohol is involved. (21)
Alcohol abuse costs more than $185 billion dollars a year. (22)
Even moderate drinking carries some risks. Alcohol can disrupt sleep. Its ability to cloud judgment is legendary. Alcohol interacts in potentially dangerous ways with a variety of medications, including acetaminophen, antidepressants, anticonvulsants, painkillers, and sedatives. It is also addictive, especially for people with a family history of alcoholism.
Alcohol Increases Risk of Developing Breast Cancer
There is convincing evidence that alcohol consumption increases the risk of breast cancer. (23, 24) In a combined analysis of six large prospective studies involving more than 320,000 women, researchers found that having two or more drinks a day increased the chances of developing breast cancer as much as 41 percent. (23)
This doesn’t mean that 40 percent or so of women who have two drinks a day will get breast cancer. Instead, it is the difference between about 12.7 of every 100 women developing breast cancer during their lifetime—the current average risk in the US—and 17 to 18 of every 100 women developing the disease. This modest increase would translate to significantly more women with breast cancer each year.
Adequate daily intake of folate, at least 600 micrograms a day, appears to mitigate this increased risk. (25, 26) (Read more about folate and alcohol.)
Genes Play a Role
Twin, family, and adoption studies have firmly established that genetics plays an important role in determining an individual’s preferences for alcohol and his or her likelihood for developing alcoholism. Alcoholism doesn’t follow the simple rules of inheritance set out by Gregor Mendel. Instead, it is influenced by several genes that interact with each other and with environmental factors. (1)
There is also some evidence that genes influence how alcohol affects the cardiovascular system. An enzyme called alcohol dehydrogenase helps metabolize alcohol. One variant of this enzyme, called alcohol dehydrogenase type 1C (ADH1C), comes in two “flavors.” One quickly breaks down alcohol, the other does it more slowly. Moderate drinkers who have two copies of the gene for the slow-acting enzyme are at much lower risk for cardiovascular disease than moderate drinkers who have two genes for the fast-acting enzyme. (27) Those with one gene for the slow-acting enzyme and one for the faster enzyme fall in between.
It’s possible that the fast-acting enzyme breaks down alcohol before it can have a beneficial effect on HDL and clotting factors. Interestingly, these differences in the ADH1C gene do not influence the risk of heart disease among people who don’t drink alcohol. This adds strong indirect evidence that alcohol itself reduces heart disease risk.
Shifting Benefits and Risks
The benefits and risks of moderate drinking change over a lifetime. In general, risks exceed benefits until middle age, when cardiovascular disease begins to account for an increasingly large share of the burden of disease and death.
For a pregnant woman and her unborn child, a recovering alcoholic, a person with liver disease, and people taking one or more medications that interact with alcohol, moderate drinking offers little benefit and substantial risks.
For a 30-year-old man, the increased risk of alcohol-related accidents outweighs the possible heart-related benefits of moderate alcohol consumption.
For a 60-year-old man, a drink a day may offer protection against heart disease that is likely to outweigh potential harm (assuming he isn’t prone to alcoholism).
For a 60-year-old woman, the benefit/risk calculations are trickier. Ten times more women die each year from heart disease (460,000) than from breast cancer (41,000). However, studies show that women are far more afraid of developing breast cancer than heart disease, something that must be factored into the equation.
The Bottom Line: Balancing Risks and Benefits
Given the complexity of alcohol’s effects on the body and the complexity of the people who drink it, blanket recommendations about alcohol are out of the question. Because each of us has unique personal and family histories, alcohol offers each person a different spectrum of benefits and risks. Whether or not to drink alcohol, especially for “medicinal purposes,” requires careful balancing of these benefits and risks.
Your health-care provider should be able to help you do this. Your overall health and risks for alcohol-associated conditions should factor into the equation. If you are thin, physically active, don’t smoke, eat a healthy diet, and have no family history of heart disease, drinking alcohol won’t add much to decreasing your risk of cardiovascular disease.
If you don’t drink, there’s no need to start. You can get similar benefits with exercise (beginning to exercise if you don’t already or boosting the intensity and duration of your activity) or healthier eating. If you are a man with no history of alcoholism who is at moderate to high risk for heart disease, a daily alcoholic drink could reduce that risk. Moderate drinking might be especially beneficial if you have low HDL that just won’t budge upward with diet and exercise.
If you are a woman with no history of alcoholism who is at moderate to high risk for heart disease, the possible benefits of a daily drink must be balanced against the small increase in risk of breast cancer.
If you already drink alcohol or plan to begin, keep it moderate—no more than two drinks a day for men or one drink a day for women. And make sure you get plenty of folate, at least 600 micrograms a day.