Quick Facts

• Both caffeinated and decaffeinated coffee improved mood, stress levels, and cognitive function in a 62-person study
• Coffee altered gut bacteria linked to better mental health, including increased levels of mood-regulating microbes
• Decaf coffee specifically improved memory and learning, while caffeinated coffee reduced anxiety and boosted attention

Coffee delivers mental health benefits that go far beyond caffeine, according to groundbreaking research published in Nature Communications. The study reveals that both regular and decaffeinated coffee improve mood and cognitive function by reshaping the gut microbiome.

Researchers at APC Microbiome Ireland studied 62 participants over several weeks. Half were regular coffee drinkers who consumed 3-5 cups daily. The other half avoided coffee entirely.

All participants stopped drinking coffee for two weeks. Researchers then gave half the group caffeinated coffee and half decaffeinated coffee without telling them which type they received.

Both groups showed significant improvements in mood. Participants reported lower stress, reduced depression, and less impulsivity regardless of whether they drank regular or decaf coffee.

Different Benefits for Each Type

The type of coffee mattered for specific benefits. Caffeinated coffee provided stronger reductions in anxiety and better attention. It also improved blood pressure.

Decaffeinated coffee delivered unique advantages. Only decaf drinkers showed clear improvements in learning and memory. They also reported better sleep quality and higher physical activity levels.

“Only participants who consumed decaffeinated coffee showed clear improvements in learning and memory, suggesting that compounds other than caffeine, such as polyphenols, may drive these cognitive effects,” the researchers noted.

Gut Bacteria Drive the Benefits

The study uncovered how coffee works at the biological level. Both types of coffee altered gut bacteria in ways that improved mental health.

Coffee drinkers showed higher levels of specific beneficial bacteria. Eggertella species and Cryptobacterium curtum increased significantly. These microbes help produce acids that protect against harmful bacteria and support digestive health.

The research also found increased Firmicutes bacteria, previously linked to positive emotions in women.

“Coffee is more than just caffeine — it’s a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being,” said lead researcher Professor John Cryan.

Timing Matters for Maximum Benefits

Experts recommend drinking coffee mid-morning, about 90 minutes after waking. This timing aligns with natural cortisol rhythms and prevents overstimulation.

The European Food Safety Authority considers 3-5 cups daily safe for most adults. This amount provides up to 400mg of caffeine, within established safety guidelines.

The findings suggest coffee functions as more than a stimulant. It acts as a functional food that supports mental wellness through complex gut-brain interactions.

“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,” Cryan added.

Read more: Coffee Impacts Mood, Memory, Stress, & Anxiety — And It’s Not Just Caffeine