Daily Coffee Drinkers Have a Gut Bacterium Most People Never Knew Existed

If you drink coffee every day, there is a good chance you are carrying higher levels of a little-known gut bacterium — and a large new study suggests the two things are directly connected. The microbe is called Lawsonibacter asaccharolyticus, and most people have never heard of it. That may be about to change.

Researchers analyzed stool samples and dietary data from tens of thousands of people across the United States and the United Kingdom, and the same pattern kept showing up: the more coffee someone drank, the more of this particular bacterium they tended to carry. It was one of the most consistent diet-microbiome links the researchers found.

For the hundreds of millions of people who reach for a cup every morning, the finding raises a genuinely interesting question — not just about coffee, but about what our daily habits are quietly doing to the microbial world living inside us.

What the Research Actually Found

The study drew on detailed dietary information from 22,867 people in the US and UK, then cross-referenced those findings against public microbiome datasets covering an additional 54,198 samples. That is a large evidence base, and it matters — diet studies often produce results that only hold up in one group and fall apart everywhere else.

This one did not fall apart. The coffee signal kept reappearing across different cohorts, which gave the researchers considerably more confidence in what they were seeing.

The standout finding was the sheer scale of the difference in Lawsonibacter asaccharolyticus levels between coffee drinkers and non-drinkers. In several cohorts, heavy coffee drinkers had roughly 4.5 to 8 times higher typical abundance of the bacterium compared to people who did not drink coffee at all. Moderate drinkers also showed elevated levels, though not as high.

Lab tests went a step further and suggested that coffee can actually help this bacterium grow — meaning the relationship does not appear to be coincidental. Something in coffee seems to be actively supporting the microbe’s presence in the gut.

Meet the Bacterium Most People Have Never Heard Of

Lawsonibacter asaccharolyticus is not a household name, even by gut microbiome standards. It was only first isolated in 2018, which makes it a genuinely recent addition to the scientific understanding of what lives in the human digestive system.

Because it is so newly described, researchers are still working out exactly what role it plays — whether it is simply a neutral passenger that thrives on coffee compounds, or whether its presence has measurable effects on health. The current study does not fully answer that question, but identifying the bacterium and its strong link to coffee consumption is a significant first step.

What makes this finding particularly interesting to scientists is that coffee is one of the most widely consumed beverages on the planet. A gut microbe that responds this strongly and consistently to a single dietary habit could turn out to be a useful marker — or even a meaningful player — in understanding coffee’s broader effects on health.

The Numbers Behind the Discovery

The study’s dataset was unusually broad by the standards of microbiome research. The primary dietary analysis covered nearly 23,000 people, and the pattern was then validated against more than 54,000 additional microbiome samples from public databases. Replication across that many independent datasets is rare and adds real weight to the conclusion.

• Primary dietary dataset: 22,867 participants (US and UK)
• Validation microbiome datasets: 54,198 samples
• Bacterium first isolated: 2018
• Abundance difference in heavy drinkers: approximately 4.5 to 8 times higher than non-drinkers
• The finding replicated across multiple independent cohorts

Why This Matters for Everyday Coffee Drinkers

The gut microbiome has become one of the most studied areas in health research over the past decade, and for good reason. The trillions of microbes living in the digestive system influence everything from how food is broken down to what chemicals end up circulating in the bloodstream. Changes in microbial composition have been linked — with varying degrees of evidence — to metabolism, immune function, and even mood.

Coffee has its own long track record in health research, with studies associating regular consumption with various outcomes. But the precise mechanisms have often remained unclear. This research points toward the gut microbiome as one possible piece of that puzzle — a specific, measurable biological change that happens in people who drink coffee regularly.

For now, the finding does not tell daily coffee drinkers to change anything. The research identifies a strong association and a plausible biological mechanism, but it does not yet establish whether higher levels of Lawsonibacter asaccharolyticus are beneficial, neutral, or something else entirely.

What Researchers Still Need to Work Out

The study, published as an open-access paper, opens more questions than it closes — which is how science is supposed to work. The immediate next steps involve understanding what Lawsonibacter asaccharolyticus actually does once it is present in higher numbers.

Researchers will likely want to identify which specific compounds in coffee are driving the bacterium’s growth. Coffee is chemically complex, containing caffeine, polyphenols, chlorogenic acids, and dozens of other compounds, any of which could theoretically be acting as a growth factor for this particular microbe.

There is also the question of whether the bacterium’s abundance changes if someone stops drinking coffee, and whether decaffeinated coffee produces the same effect. Those answers would help isolate exactly what is driving the relationship.

For now, the finding stands as a reminder that the things we consume every day — even something as routine as a morning cup of coffee — are shaping the microscopic ecosystem inside us in ways science is only beginning to map.

Frequently Asked Questions

What is Lawsonibacter asaccharolyticus?
It is a gut bacterium first isolated in 2018. Research has found it appears in significantly higher levels in people who drink coffee regularly compared to non-drinkers.

How much more of this bacterium do coffee drinkers have?
According to the study, heavy coffee drinkers had approximately 4.5 to 8 times higher typical abundance of the bacterium compared to people who do not drink coffee.

How large was the study that found this?
Researchers analyzed dietary data from 22,867 people in the US and UK, then validated the findings against public microbiome datasets totaling 54,198 samples.

Does this mean coffee is good or bad for gut health?
The study identifies a strong association between coffee drinking and elevated levels of this bacterium, but does not yet establish whether those elevated levels are beneficial, harmful, or neutral.

Does the bacterium actually grow because of coffee?
Lab tests included in the research suggested that coffee can help Lawsonibacter asaccharolyticus grow, pointing toward a direct biological relationship rather than a coincidental one.

Should coffee drinkers change their habits based on this research?
The research does not recommend any change in behavior — it identifies an association and a potential mechanism, but further studies are needed before any practical guidance could be drawn from the findings.