What does alcohol do to your immune system?

Heavy or prolonged drinking suppresses several components of your immune system at the same time. Both the fast, broad first-line response (the innate immune system) and the more targeted defences that remember specific pathogens (the adaptive system) are affected. The result is a considerably higher risk of serious infections, including tuberculosis, pneumonia and hepatitis. This relationship is well documented across multiple studies.

A major part of that damage runs through the gut. Alcohol disrupts the bacterial balance in the gut, damages the gut wall and reduces the production of protective substances that keep bacteria at bay. This allows bacteria and bacterial waste products to leak more easily through the gut wall into the bloodstream. That activates the immune system in a harmful way and worsens liver disease. In addition, people with alcohol-related liver disease show a reduction in a specific immune protein on liver macrophages (the liver's 'sentinel cells'). As a result, the liver clears bacteria arriving from the gut less efficiently.

Chronic heavy drinking also throws the liver's balance between pro-inflammatory and anti-inflammatory immune functions out of equilibrium. This persistent state of inflammation leads to scar tissue in the liver (fibrosis) and ultimately serious liver disease. This mechanism is solidly supported by evidence.

Moderate drinking presents a different, more nuanced picture. Observational studies sometimes find lower inflammatory activity and a slightly better response to vaccinations in moderate drinkers than in people who drink either not at all or heavily. This applies particularly to polyphenol-rich drinks such as wine and beer. However, these are observational studies, not experiments; exactly how this works is unclear, and drinking pattern, sex and drink choice all play a role. No recommendation can be based on this.

Finally, drinking during pregnancy can disrupt the still-developing immune system of the baby. Both animal and human research shows increased susceptibility to infection in newborns, possibly with long-lasting consequences. Moreover, alcohol increases the risk of premature birth, which is itself a risk factor for immune problems.