While we've discussed the dangerous effects of alcohol abuse and misuse, that doesn't mean it's always bad. Besides being part of many complex and delicious beverages, there are any number of studies which show that alcohol may be linked to health benefits. That doesn't mean that it's all good news either, or that the evidence is a slam dunk. There's certainly enough though to warrant a thorough review. And that's the topic of this week's Healthcare Triage.

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The study of how alcohol consumption affects health isn't new. In 1990 a prospective cohort study, including more than 275,000 men, followed since 1959, was published. Compared to those who never drank alcohol, those who consumed one to two drinks a day had a significantly reduced risk of death from both coronary heart disease as well as 'all causes'. Those who consumed three or more drinks a day still had a lower risk of death from coronary heart disease. But they had a higher risk of death overall.

A 2004 study came to similar conclusions. It followed about 6,600 men and 8,000 women for five years and found that compared to 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 a journal called Alcoholism: Clinical and Experimental Research agreed that moderate drinking seems to be associated with a decreased risk of death overall.

However, alcohol has different effects on different causes of death. Almost all of the major benefits of drinking are seen in cardiovascular illness. 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 on average increases the relative, but not absolute, risk of breast cancer by a statistically significant, but small, 2%. A meta-analysis of colorectal cancer and alcohol found that heavy drinkers, but not light or moderate drinkers, were at an increased risk of the disease. No relationship was 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 is associated with non-death related benefits too. A cohort of about 6,000 people followed in the UK 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% lower rates of diabetes compared to non-drinkers. Heavy drinkers though, had an increased risk of diabetes.

This is where savvy viewers should be asking about randomised controlled trials. After all, epidemiologic evidence and associations can only get us so far. Recently, in Annals of Internal Medicine, such a trial was published. Patients with well-controlled type 2 diabetes were randomised to drink either 150 milliliters of water, white wine or red wine with thinner for two years. The beverages were provided to patients free of charge. They were all placed on a Mediterranean diet with no calorie restrictions. They found that those who drink the wine, most notably the red wine, had a reduction in cardiometabolic risk factors. This was especially true in patients who had a genotype making them slow ethanol metabolizers. No significant adverse effects were seen from the intervention. In another analysis of that same randomised controlled trial published earlier this year, the main outcome of interest was blood pressure. In that study, the fast ethanol metabolizers saw a reduction in systolic blood pressure of eight milligrams of mercury. Again, no significant adverse effects were seen. This contradicted the findings from systematic reviews of epidemiologic studies that show alcohol intake to be associated with a small but significant increase in blood pressure. Adding further complications was a shorter-term randomised controlled trial looking at red wine consumption that found it had no effect, positive or negative, with respect to blood pressure in patients with atherosclerosis. A different analysis of that same 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, or the good cholesterol. There was even a dose-response with more alcohol consumed having more of an effect. Synthesizing 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 seem to outweigh all of the losses in other diseases combined though. The most recent report of the USDA Scientific Advisory Panel agrees with that assessment. However, alcohol isn't harmless. Many people with certain diseases or disorders, and women who are pregnant need to avoid it. Others can't keep their consumption to acceptable levels. Alcohol is very, very harmful when abused. So much so that it's difficult to tell people to start drinking. That's rarely the conclusion of any studies or editorials about alcohol. No matter how positive the results may be. Nor is it the advice any doctors I know give. However, the evidence does seem to say that a moderate consumption is safe, and it may even be healthy for many. If you're enjoying some drinks responsibly, it's nice to know that they may be doing more than just bringing you cheer.

Healthcare Triage is supported in part by viewers like you through patreon.com, a service that allows you to support the show through a monthly donation. Your support makes this show bigger and better. We'd especially like to thank our research associate Joe Sevits, give a special shout-out to Johnathan Dunn, and thank our surgeon admiral, Sam. Thanks Joe and John! Thanks Sam! More information can be found at patreon.com/healthcaretriage.