The thought of a steaming cup of coffee helps to pull many people worldwide out of bed in the morning. Scientists have consistently linked this ubiquitous drink to lowered risks for maladies such as heart disease, colon cancer and type 2 diabetes. But its effects on the gut microbiome—the intestinal bacterial population thought to help mediate between diet and health—are largely unknown.
In the largest-ever study on the relation between coffee and the gut microbiome, published recently in Nature Microbiology, researchers looked at fecal DNA from more than 20,000 participants who tracked their daily coffee consumption. The scientists found that regular coffee drinking was linked to the growth of a specific gut bacterium called Lawsonibacter asaccharolyticus. “For this, you really need these large dataset approaches that haven’t been possible until recently,” says Peter Belenky, a microbiologist at Brown University who was not affiliated with the study.
L. asaccharolyticus, which was first described in 2018, is a relatively understudied bacterium known to produce butyrate, a marker of adequate gut fermentation that indicates proper digestion and nutrient absorption. “We don’t know too much about this bug,” Belenky says, “but we can place it as likely a fairly good bacterium.”
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Studies on diet and the microbiome typically link multiple bacterial species to a specific dietary factor or vice versa. In this one, the researchers discovered that coffee drinking correlated with an increase in several bacterial species, but the correlation with L. asaccharolyticus growth was by far the strongest, even with decaffeinated coffee. And feeding coffee to L. asaccharolyticus growing on petri dishes made the microbes grow faster. “It’s very unique that we found this very strong, very distinct one-to-one match,” says Harvard University epidemiologist Mingyang Song, a co-senior author on the study.
To find out what this bug might be doing in the gut, the team looked at the metabolites from a few hundred study participants’ blood. They found that an increase in quinic acid, part of a subgroup of polyphenols (antioxidants that can, in the right context, reduce inflammation), was strongly associated with L. asaccharolyticus growth. So was hippurate, a compound whose levels indicate greater microbial diversity and therefore better gut health.
Given these results, the scientists are now “trying to link these bacteria and the related metabolites to health outcomes,” Song says. “That can tell us whether the bacteria are really mediating the health benefits of coffee.”
Analyzing these gigantic population-based datasets is an effective strategy to parse out specific relations between things we ingest and the bugs in our gut. “Maybe this will open up a more extensive approach to food research,” Belenky says.