Caffeine may be able to tamp down the inflammation that worsens with age, according to a study that investigated caffeine’s effects on immune cells. It’s a correlational study, but it’s one that dives into how caffeine could be affecting the immune system. The findings could help explain why coffee has been purported to help ward off everything from type 2 diabetes to cardiovascular disease and even dementia.

It’s comforting news for those of us who were already reaching for that second caffeine hit

True, there’s a long list of studies that have found a correlation between caffeine, coffee, and better health; there have also been a few that say coffee, especially hot coffee, can increase your risk for certain cancers. But today’s study is one of the few that looks at exactly how caffeine affects the immune system. We’ve known for some time that caffeine can block the effects of a molecule called adenosine; blocking adenosine receptors on brain cells is thought to be how caffeine wakes us up. But in the body, blocking adenosine may also block pathways that produce inflammatory molecules, according to results published today in the journal Nature Medicine.

“That something many people drink — and actually like to drink — might have a direct benefit came as a surprise to us,” Mark Davis, a professor at Stanford and senior author of the study, said in a news release. While he and his colleagues didn’t prove that caffeine causes better health, they did come up with a possible way it could be doing so. “What we’ve shown is a correlation between caffeine consumption and longevity. And we’ve shown more rigorously, in laboratory tests, a very plausible mechanism for why this might be so.”

It started as an aging study. Researchers from Stanford University and the University of Bordeaux analyzed the genes of 114 people who were enrolled in a long-term research study. The scientists weren’t looking at the genetic code itself, but how much people were using specific genes to produce proteins.

Older people tend to ramp up production of inflammatory immune molecules

They found that older people between the ages of 60 and 89 tend to ramp up production of immune molecules in a complex called the inflammasome. That’s a clump of immune proteins inside cells that activate one of the immune system’s big guns, called interleukin 1 beta or IL-1B. It’s an important molecule for fighting off infection, but too much of it for too long has been linked with chronic diseases like heart disease, cancer, and Alzheimer’s disease.

Among the older people in the study, 12 of them made much more of these inflammatory molecules, and 11 people made much less. The less-inflamed group was also healthier, with lower blood pressure, more flexible arteries, and more relatives who lived past age 90.

They also had lower levels of the breakdown products of DNA and RNA circulating in their blood, including one molecule called adenine, and another called adenosine — which is adenine attached to a sugar molecule. These molecules are known to stimulate the inflammasome, and lower levels of them could explain why this group was less inflamed. In fact, treating cells with these breakdown products made them churn out more inflammatory molecules, and made mice more inflamed, with higher blood pressure.

Higher blood levels of caffeine correlated with less inflammation

That’s where the caffeine comes in. Caffeine is known to block the effects of adenosine in the brain — that’s how scientists think it keeps us awake. So, the researchers suspected that it’s possible that it could block the effects of adenine and adenosine on immune cells, too, and reduce their ability to cause inflammation. According to a questionnaire, people in the less inflamed group consumed more caffeinated beverages like coffee, soda, and tea. In fact, higher blood levels of caffeine and other caffeine breakdown products correlated with lower production of inflammatory molecules like IL-1B.

When the scientists treated cells with adenine and another molecule known to trigger the inflammasome, the cells that were soaking in caffeine produced far lower levels of inflammatory molecules. The researchers still haven’t fully explained how caffeine is interfering with inflammation. And the results aren’t enough to base any behavioral recommendations off of; but it’s comforting news for those of us who were already reaching for that second hit of caffeine anyway.