After drinking for seven months, the macaques received another booster shot, and their reactions were remarkably different. The immune systems of the bad monkeys that drank too much failed to produce the antibodies the body usually makes in response to a vaccine. The moderate drinkers, on the other hand, demonstrated an enhanced immune response—better even than the teetotaling control group. The researchers can’t yet fully explain the results, but one possible explanation is that modest amounts of alcohol stimulate the immune system.

The benefits of moderate drinking are well documented, from reduced risk of Alzheimer’s to improved cardiovascular function. But while a glass or two of wine with dinner might promote health, the researchers emphasized that excessive alcohol consumption is deleterious to immune function, no matter how merry one may feel.