A study of 61 healthy adults found that regular coffee drinkers had a more diverse gut microbiome, though it does not prove cause and effect.
- The study followed 61 healthy adults for 9 days, split into a low-coffee group and a regular-coffee group.
- The regular drinkers had a richer gut bacterial community, including bacteria that break down plant compounds found in coffee.
- They also had a lower pH (a more acidic environment) in the small intestine, plus signs of caffeine metabolism alongside stronger colon contractions.
- This is a small observational study, so it cannot conclude that coffee is the cause.
- If you already drink coffee, there is no need to change your habits because of this study. Just listen to how your body responds.
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Your morning cup does more than wake you up
Besides caffeine, coffee contains polyphenols, a group of plant compounds that gut bacteria can break down. A recent study, covered by mindbodygreen, asks whether a daily coffee habit is related to the kinds of bacteria living in the gut.
The authors followed 61 healthy adults for 9 days. Participants kept food diaries and provided urine and stool samples. Some also swallowed wireless capsules to measure digestive activity, including muscle contractions and acidity.
Based on the diaries, participants were split into two groups. The low-coffee group drank coffee on fewer than 3 days. The regular group drank it on more than 3 days.
How the two groups differed
The two groups were fairly similar in age, BMI, and overall diet. Even so, their gut microbiomes differed. The regular drinkers had more bacterial strains, including some that break down coffee's plant compounds at higher levels.
Digestive activity also differed. Signs of caffeine metabolism coincided with stronger contractions in the colon, the organ that moves digested food along. In the small intestine, the regular drinkers had a lower pH, meaning a more acidic environment. Because acidity affects which bacteria can survive, this may explain part of the gap.
Why bacterial diversity matters
The gut microbiome plays a well-established role in overall health, including breaking down substances the body cannot digest on its own. A more diverse bacterial community is generally associated with a more resilient gut ecosystem, since each species handles a different job.
Coffee may act through both polyphenols and caffeine. Polyphenols feed certain bacteria that break them down, while caffeine may influence the rhythm of gut motility. However, the exact mechanism remains unclear. The study only observed people's existing habits, so it cannot say whether coffee causes these differences.
How to drink coffee sensibly
If you enjoy coffee, there is no need to change your habits based on a single study. A few things are worth noting. Coffee stimulates digestion, so many people feel the urge to use the bathroom right after a cup. If your usual amount upsets your stomach, cutting back is perfectly fine.
More is not necessarily better. The study did not determine an ideal daily amount, nor did it show that drinking more is beneficial. Polyphenol content also varies with the bean, the roast level, and the brewing method, so the effect on gut bacteria may differ. As for decaf, the study does not say whether it has a similar effect. That is a direction worth watching in future research.
In short, the regular drinkers in this small study had a more diverse microbiome and different digestive activity. Larger, longer studies are needed to understand the connection.
In Vietnam, a cup of coffee often comes with condensed milk, sugar, or ice, while the study did not analyze these factors. So don't treat the results as a reason to drink more. The smallest experiment you can run: keep your usual number of cups, and for a few days note how your stomach feels after each one. If you feel queasy or uncomfortable, cut back or change how you brew it.
Source: mindbodygreen
Reviewed by: Hero Association
