University College Cork Researchers Link Regular and Decaf Coffee to Gut Microbiome Shifts
Coffee consumption alters the composition of the human gut microbiome regardless of whether the beverage contains caffeine, according to a study reported by Gezondnu. Researchers at University College Cork found that both regular and decaffeinated coffee prompt shifts in gut bacteria among regular drinkers, pointing to non-caffeine plant compounds as active agents in the digestive tract.
Two-Week Elimination Protocol Reveals Bacterial Fluctuations
The study tracked 62 healthy adult volunteers aged 30 to 50, dividing them into two baseline groups: 31 individuals who abstained from coffee entirely and 31 regular drinkers who consumed three to five cups daily. The regular coffee drinkers underwent a two-week elimination phase where they stopped consuming coffee completely, followed by a three-week reintroduction period where they drank four cups daily of either regular or decaffeinated coffee.
Analysis of stool and urine samples collected throughout the trial revealed that regular coffee drinkers hosted different proportions of specific bacterial groups, notably Eggerthella and Cryptobacterium, compared to non-drinkers. When habitual drinkers stopped consuming coffee, measurable shifts occurred in their fecal bacterial composition and metabolite profiles, which changed again once coffee consumption resumed.
Divergent Effects on Stress, Memory, and Alertness
Beyond the gastrointestinal tract, the investigation monitored the gut-brain axis by assessing participants’ self-reported stress, mood, and cognitive performance. Following the reintroduction of coffee, participants across both groups reported lower average stress levels and fewer depressive symptoms. Specific cognitive benefits diverged based on the beverage type: decaffeinated coffee drinkers showed improvements in memory and learning tasks, while regular caffeinated coffee drinkers demonstrated advantages in attention and alertness.
Remaining Unknowns in Long-Term Gut Health
The exact plant compounds responsible for the microbial shifts remain unidentified, though researchers point to polyphenols—plant-based molecules partially broken down by gut bacteria—as primary candidates. Scientists emphasize that altered bacterial ratios do not automatically equate to improved digestive function or a healthier microbiome, and the long-term clinical significance of these shifts is still not clear.
Frequently Asked Questions
Does switching to decaf provide the same gut benefits as regular coffee?
The study showed that decaf alters gut bacteria just like regular coffee, indicating that non-caffeine compounds drive the microbial shift. However, researchers caution that a change in bacterial composition does not necessarily mean an improvement in gut health.
How much coffee did participants consume during the trial?
The 31 habitual coffee drinkers in the study consumed four cups daily of either regular or decaffeinated coffee during the three-week reintroduction phase, following a strict two-week elimination period.
Can drinking coffee improve memory or cognitive function?
Participants consuming decaf showed improvements in certain memory and learning tasks, while those drinking regular coffee exhibited better attention and alertness. Researchers note the trial was small and short-term, meaning long-term cognitive benefits are not yet proven.
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