A new scientific study has found that drinking up to four cups of coffee daily may positively influence mood and stress levels, shedding light on the beverage’s broader impact beyond just boosting energy.

The research, conducted by APC Microbiome Ireland at University College Cork and published in Nature Communications, highlights a strong connection between coffee consumption, gut health, and emotional well-being.

According to the study, changes in mood and stress were closely linked to shifts in gut bacteria and certain metabolic compounds. Interestingly, these effects were observed with both caffeinated and decaffeinated coffee, suggesting that coffee’s benefits extend beyond caffeine alone.

“Coffee is more than just caffeine,” said lead researcher John Cryan, PhD. “It’s a complex dietary factor that interacts with our gut microbes, metabolism, and even emotional health.”

The study builds on existing knowledge of the “gut-brain axis,” a two-way communication system between the digestive system and the brain. Gut microbiota—trillions of microorganisms living in the digestive tract—play a crucial role in this relationship, influencing both physical and mental health.

To investigate further, researchers initially compared 31 regular coffee drinkers (consuming 3–5 cups daily) with 31 non-coffee drinkers. Participants underwent a range of assessments, including tests on cognitive function, stress, mood, immune health, and gut microbiome composition.

The coffee-drinking group then abstained from coffee and other caffeine sources for two weeks. After this break, they resumed coffee consumption for 21 days—half consuming caffeinated coffee and the other half decaffeinated—while drinking four servings daily.

Researchers monitored participants throughout the withdrawal and reintroduction phases, tracking how changes in coffee intake affected both gut health and psychological well-being.

The findings suggest that coffee may play a meaningful role in supporting mental health through its interaction with the gut microbiome, although researchers note that further studies are needed to fully understand the underlying mechanisms.

With growing public interest in gut health, this study adds to the evolving understanding of how everyday dietary choices can influence both body and mind.