It's no secret that excessive alcohol consumption damages the liver, but a new study reveals a previously unknown vicious cycle that makes that damage worse. Chronic alcohol use makes it easier for bacteria to leak out of the gut and migrate to the liver, causing further harm.

The new study, led by scientists at the University of California San Diego, examined human liver biopsies as well as mouse models of alcohol-associated liver disease. The team found that chronic alcohol use impaired the production of a cellular signaling protein called mAChR4 in the small intestine.

Lower levels of this protein were found to interfere with the formation of what are called goblet cell-associated antigen passages (GAPs). These specialized structures play a key role in teaching the immune system to respond to microbes, particularly those that escape the gut into other parts of the body, where they don't belong.