Heavy drinking is clearly bad for your health. But it's long been questioned whether moderate drinking is also risky -- and, if so, how risky, exactly.

Health researchers have consistently found links between alcohol consumption and several types of cancers (namely mouth, throat, colon, rectal, liver, and breast), as well as liver diseases, injuries, and traffic accidents. But nailing down the health risks from the lower levels of drinking has been tricky. For one, much of the data on moderate drinking are from observational studies in different countries, cultures, and populations. They cannot determine if alcohol is the direct cause of any given association, and they may be swayed by other lifestyle factors. The resulting data can be noisy and inconsistent.

Moreover, many studies rely on people to self-report whether they drink and, if so, how much, which is problematic because people may not accurately assess and/or report how much they actually drink. A related problem is that studies in the past often compared drinkers to people who said they didn't drink. But, the trouble is, non-drinking groups are often some mix of people who are lifelong abstainers and people who used to drink but quit for some reason -- maybe because of health effects. This latter group has the potential to have lingering health effects from their drinking days, which could skew any comparisons looking for health differences.

Then there's the larger, common problem with any research focused on food or beverages: some have been sponsored or somehow swayed by industry, casting suspicion on the findings, particularly the ones indicating benefits. This has been a clear problem for alcohol research. For instance, in 2018, the National Institutes of Health shut down a $100 million trial aimed at assessing the health effects (and potential benefits) of moderate drinking after it came to light that much of the funding was solicited from the alcohol industry. There was a lot of questionable communication between NIH scientists and alcohol industry representatives.