Research into how alcohol consumption affects health has been going on for a long time. According to reports, a 1990 prospective cohort study included results of more than 275,000 men followed since 1959. Compared with those who never drank alcohol, those who consumed one to two drinks a day had a significantly reduced mortality rate from both coronary heart disease and “all causes.” Those who consumed three or more drinks a day still had a lower risk of death from coronary heart disease, but had a higher mortality rate over all.
A 2004 study came to similar conclusions. It followed about 6,600 men and 8,000 women for five years and found that compared with those who drank about one drink a day on average, those who didn’t drink at all and those who drank more than two drinks a day had higher rates of death. Results like these have been consistent across a number of studies in different populations. Even studies published in the journal Alcoholism: Clinical and Experimental Research agree that moderate drinking seems to be associated with a decreased risk of death over all.
However, alcohol seems to have different effects on different diseases. Almost all of the major benefits of drinking are seen in cardiovascular illnesses. In fact, with men, even consumption of a surprisingly large amount can seem protective.
When it comes to cancer, the picture isn’t as rosy. For instance, a 2007 study involving the Women’s Health Study cohort found that increased alcohol consumption was associated with an increased risk of breast cancer. More broadly, a 2014 systematic review of epidemiologic and experimental studies looking at alcohol and breast cancer found that the overall consensus is that each additional drink per day increases the relative risk (comparing the risk in two groups) of breast cancer by a statistically significant, but small, 2 percent — although not the absolute risk.
A meta-analysis of colorectal cancer and alcohol found that heavy drinkers, but not light or moderate drinkers, were at increased risk of the disease. No relationship is seen with respect to bladder cancer or ovarian cancer. A study that included all cancers found that light drinking was protective; moderate drinking had no effect; and heavy drinking was detrimental.
Moderate alcohol consumption has been found to be associated with other benefits, though. A cohort of about 6,000 people followed in Britain found that those who consumed alcohol at least once a week had significantly better cognitive function in middle age than those who did not drink at all. This protective effect on cognition was seen in people who drank up to 30 drinks a week.
A 2004 systematic review found that moderate drinking was associated with up to 56 percent lower rates of diabetes compared with nondrinkers. Heavy drinkers, though, had an increased incidence of diabetes. This is where savvy readers should be asking: What about randomized controlled trials? After all, epidemiologic evidence and associations only go so far; they cannot get us to causation.
Recently, in Annals of Internal Medicine, such a trial was published. Patients with well-controlled Type 2 diabetes were randomized to drink 150 milliliters of water, white wine or red wine with dinner for two years. The beverages were provided to patients free of charge. They were all placed on a Mediterranean diet with no calorie restrictions.
Researchers found that those who drank the wine, most notably red wine, had a reduction in cardiometabolic risk factors, or those for heart disease, diabetes or stroke. This was especially true in patients who had certain genotypes. Further, no one had any significant adverse effects from being randomized to drink the alcohol.
In another analysis of that randomized control trial published this year, the most interesting finding was about blood pressure. In this study, some people saw a reduction in systolic blood pressure. Again, the alcohol was not associated with significant adverse effects. This contradicts the findings from systematic reviews of epidemiologic studies that show alcohol intake may be associated with a small but significant increase in blood pressure.
Adding further complications was a shorter-term trial looking at red wine consumption that found it had no effect, positive or negative, on blood pressure in patients with atherosclerosis. A different analysis of that study found that it did result in improved cholesterol levels, even though many patients were already being treated with statins.
A 2011 meta-analysis examined 63 controlled trials of wine, beer and spirits, and found that all of those beverages increased levels of HDL cholesterol (the good cholesterol). There was even a dose-response, with more alcohol consumed having more of an effect.
Synthesizing all this, there seems to be a sizable amount of evidence that moderate alcohol consumption is associated with decreased rates of cardiovascular disease, diabetes and death. It also seems to be associated with increased rates, perhaps to a lesser extent, of some cancers, especially breast cancer, as well as some other diseases or conditions. The gains from improved cardiovascular disease deaths seem to outweigh all of the losses in other diseases combined. The most recent report of the U.S.D.A. Scientific Advisory Panel agrees with that assessment.
But alcohol isn’t harmless. Many people with certain diseases or disorders, and women who are pregnant, need to avoid it. Others who can’t keep their consumption to acceptable levels need to abstain. Alcohol is very harmful when abused, so much so that it’s difficult for me to tell people to start drinking for their health. That’s rarely the conclusion of any studies about alcohol, no matter how positive the results. Nor is it the advice any doctors I know give.
However, the evidence does seem to say that moderate consumption is safe, and that it may even be healthy for many people. If you’re enjoying some drinks this holiday season, it’s nice to know that they may be doing more than just bringing you cheer.