You're pouring your second cup of the morning when a headline pops up on your phone: coffee is "bad for your gut." Last month, a different headline said it was good for it. You stand there with the pot in your hand, unsure whether to finish the cup.
This is not your fault. Most gut-health headlines squeeze messy research into a yes-or-no answer. But one large study found something far more specific than "good" or "bad": coffee drinkers carry a lot more of one particular gut bacterium.
The bacterium that shows up with your coffee
Researchers led by the University of Trento analyzed diet and gut microbiome data from 22,867 people in the U.S. and the U.K. They then checked their findings against public data from 211 other groups, covering 54,198 people. The results were published in Nature Microbiology in late 2024.
The link between coffee and the gut came down mostly to one species, Lawsonibacter asaccharolyticus. According to the university, it was on average six to eight times more abundant in people who drank coffee regularly. The pattern held across the many populations studied.
Here's where "feeds" comes in. When the team grew the bacterium in the lab, first author Paolo Manghi explained, they saw that it grew faster when coffee was added to the culture medium. Blood tests on a subset of participants also linked quinic acid and related compounds to both coffee drinking and the bacterium.
What to do with your cup
The findings don't call for a new coffee habit. Here's how to use them:
- Don't start drinking coffee for your gut. The study found a link, not a benefit, and no one knows yet what this bacterium does for your health.
- Keep your usual cup within limits. The FDA has cited 400 milligrams of caffeine a day, about two to three 12-ounce cups of coffee, as an amount not generally associated with negative effects for most adults.
- Feed your gut on purpose with other foods. Fiber from oats, bananas, onions and beans feeds gut bacteria, and fermented foods like yogurt and kefir provide probiotics. A yogurt and oat smoothie gives you both in one glass.
Plan B if coffee doesn't agree with you: you're not missing a proven benefit. Skip it without worry.
One bacterium, not a verdict on coffee
This was an observational study. It shows that coffee drinking and L. asaccharolyticus go together, not that coffee changes your health through it. The lab growth test happened in a dish, not in a human gut.
The study also doesn't show that coffee drinkers have a "healthier" or more diverse microbiome overall. It points to a single species. As Nicola Segata, who coordinated the research, put it about the bacterium, "It does not seem to play a particularly important role," though the method could help researchers study bacteria and foods with bigger health effects.
Caffeine affects people differently. The FDA notes that some conditions and medications can make people more sensitive to it, and recommends that anyone pregnant, trying to become pregnant or breastfeeding talk with a health care provider about limiting caffeine. Your doctor or a registered dietitian can help you decide what fits.
Enjoy the cup for what it is, and feed your gut with fiber and fermented foods. That's the trick.
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