Regular coffee drinkers may carry a noticeably different mix of gut bacteria and gut-made chemicals than people who skip coffee, according to a small study from University College Cork in Ireland. The study also hints that decaf and regular coffee may affect mood and thinking in different ways.
What the Researchers Did
The team, at the APC Microbiome Ireland research center, recruited 62 adults: 31 people who drank three to five cups of coffee a day and 31 who did not drink coffee. The results were published in Nature Communications.
First, the coffee drinkers gave up coffee for two weeks while everyone completed psychological tests and provided stool and urine samples. Then coffee was reintroduced. Participants did not know whether they were getting regular or decaf; half got each.
What They Found
- Even after two weeks without coffee, the coffee drinkers’ metabolite profiles, the chemical byproducts in their samples, looked quite different from those of non-drinkers.
- Certain bacteria, including Eggerthella and Cryptobacterium curtum, were more common in coffee drinkers.
- After coffee came back, both the regular and decaf groups reported less stress, fewer depressive symptoms and lower impulsivity.
- Only the decaf group showed improvements in learning and memory tests, which the authors think may point to non-caffeine compounds such as polyphenols.
- Caffeinated coffee was linked with lower anxiety and better attention.
Lead researcher John Cryan described coffee as more than a caffeine delivery system: a complex food that interacts with gut microbes, metabolism and mood.
The Catch
This was a small, exploratory study, and the authors acknowledge it cannot prove that coffee directly causes changes in mood, memory or gut health. Mood improvements after reintroducing a daily habit may partly reflect simply getting a familiar routine back. The coverage of the study did not report effect sizes, so it is hard to judge how big the differences were. The work was also funded by the Institute for Scientific Information on Coffee, an industry-backed group, which does not make it wrong but is worth knowing.
The more useful takeaway: what is in your cup is more than caffeine, and decaf may not be the “empty” option it is sometimes treated as. If caffeine bothers your sleep or your heart rate, this is not a reason to push through.
This article is for general information, not medical advice.
More on Contoh
- Signs of Brain Aging May Show Up Decades Early, and the Gut Could Be Part of the Story
- A 20-Minute Walk Got the Gut Moving Within Minutes in a Small Study
- Cutting Ultra-Processed Food Eased Depression Symptoms in a Small Study