Drinking coffee could do far more than provide a morning boost—new research has pinpointed it as being beneficial for both gut and brain health. The study by researchers at APC Microbiome Ireland at University College Cork found that both caffeinated and decaffeinated coffee can positively affect gut bacteria, with knock-on benefits for mood and stress levels.
Gut-Brain Axis Insights
While recent research supports the long-held belief that coffee can improve digestion and boost mental well-being, the biological mechanisms behind these effects have remained unclear. For the new study into the 'gut-brain axis'—the complex communication network linking the digestive system and the brain—researchers analysed 62 participants using psychological assessments, diet tracking, and analysis of stool and urine samples. Half were regular coffee drinkers, and the other 31 people in the cohort were non-drinkers.
Regular coffee drinkers who consumed three to five cups per day were asked to give up coffee for two weeks, during which scientists observed significant changes in their gut microbiome, the bacteria living in the digestive system. When coffee was reintroduced, these participants reported lower levels of stress, depression, and impulsivity, regardless of whether they consumed caffeinated or decaffeinated coffee.
Bacterial Changes Observed
The study, published in the journal Nature Communications, found higher levels of bacteria, including Eggertella and Cryptobacterium curtum, in coffee drinkers, which are thought to play roles in digestion and may help eliminate harmful bacteria. An increase in a type of bacteria previously linked to positive emotions in women was also observed.
The type of coffee consumed appeared to influence specific outcomes. Decaffeinated coffee was linked to improved learning and memory, while caffeinated coffee was associated with reduced anxiety, improved vigilance, and better attention. This suggests compounds other than caffeine, such as polyphenols, may drive some of coffee's cognitive benefits, although caffeine itself was also linked to reduced inflammation.
Expert Commentary
Professor John Cryan, lead author of the study, said: 'Public interest in gut health has risen hugely. The relationship between digestive and mental health is also increasingly being better understood, but the mechanisms behind coffee's effects on this gut-brain axis have remained unclear. Our findings reveal the microbiome and neurological responses to coffee, as well as their potential long-term benefits for a healthier microbiome. Coffee may modify what microbes do collectively and what metabolites they use. As the public continues to think about dietary changes for the right digestive balance, coffee has the potential to also be harnessed as a further intervention as part of a healthy, balanced diet.'
Broader Health Implications
Previous studies have suggested caffeine may help protect the brain by reducing inflammation and limiting the build-up of harmful proteins linked to cognitive decline and dementia. Coffee is also naturally rich in micronutrients called polyphenols which have been shown to reduce inflammation and cellular damage in the brain, warding off the release of neurotoxins that interfere with neurotransmitters like serotonin, raising the risk of mood disorders such as depression. Coffee can also stimulate the production of the feel-good chemical dopamine, lowering the risk of anxiety and boosting motivation. Additionally, coffee can be a reflection of social support, such as meeting a friend at a coffee shop, which improves mood.
