WASHINGTON — A new study suggests that your morning brew might be doing more than just perking you up — it could be protecting you from a range of serious heart conditions. Researchers working with the Endocrine Society have found that drinking a moderate amount of coffee is associated with a lower risk of developing multiple cardiometabolic diseases. In simpler terms, your daily cup of coffee (or three) might help ward off conditions like Type 2 diabetes, heart disease, and stroke.
“Consuming three cups of coffee, or 200-300 mg caffeine, per day might help to reduce the risk of developing cardiometabolic multimorbidity in individuals without any cardiometabolic disease,” says Dr. Chaofu Ke, the lead author of the study from Suzhou Medical College in China, in a media release.
People who drink moderate amounts of wine regularly tend to have higher income, and thus better health in general. At least that's the last generally accepting hypothesis I last saw.
A problem with the older studies that seemed to indicate that alcohol had health benefits was also that their control group, the people who didn’t drink, turned out largely not to do so because they already had severe medical problems. They weren’t allowed to drink because of them.
Compared to them it looked like the people who did drink were more healthy on average. So they concluded there must be health benefits to drinking alcohol.
This “Science VS” episode is about that (and has a bunch of citations in its transcript): https://gimletmedia.com/shows/science-vs/llhdgj
The era of that was also the first time these studies were being done predominantly with non-smokers. It was hard to disentangle the health effects of smoking with everything else. Smoking rates drop through the 80s and 90s, and wine and coffee suddenly look pretty good compared to how bad we thought they were.