Caffeinated and Decaffeinated Coffee May Boost Mood and Cognitive Performance

Coffee may improve mood and cognitive performance, even when it does not contain caffeine.

A new study comparing caffeinated and decaffeinated coffee indicates that both varieties could offer benefits for the gut, mood and behaviour.

Researchers at University College Cork in Ireland compared health indicators and self-reported wellbeing in 31 people who drank three to five cups of coffee daily and 31 people who did not drink coffee.

At the beginning of the study, the groups did not differ in body mass index, blood pressure, stress, anxiety, depression, gastrointestinal symptoms, sleep quality or physical activity.

However, coffee drinkers displayed differences in certain blood immune markers and in some strains of microbes in their gut.

Caffeinated and decaffeinated coffee intervention

To determine whether caffeine was essential to these effects, the researchers asked all 31 coffee drinkers to avoid their usual coffee for two weeks.

Once this withdrawal period ended, the intervention began. Coffee was added back into participants' diets for three weeks: 16 people received caffeinated coffee and 15 received decaffeinated coffee. The participants were unaware of which type they were drinking.

After coffee was reintroduced, every participant showed coffee-related alterations in gut microbiome patterns. These included strain-level changes linked with both caffeinated and decaffeinated coffee.

This indicates that certain gut microbial strains may respond to coffee itself, regardless of whether caffeine is present.

"Both types [of coffee] lowered stress, depression, impulsivity, and inflammation, while also boosting mood and cognitive performance," the authors write.

Only caffeinated coffee, however, was associated with lower anxiety, psychological distress and blood pressure, as well as better attention and stress coping. Compared with non-coffee drinkers, coffee drinkers also had greater impulsivity and emotional reactivity at baseline and after caffeine was resumed.

Decaffeinated coffee, on the other hand, was linked with improved sleep, physical activity and memory.

Coffee, the gut microbiome and the brain

The results indicate that caffeine may exert particular effects on mood and cognition, while coffee without caffeine may still be connected to the gut-brain relationship.

"Coffee is more than just caffeine – it's a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional wellbeing," says microbiologist John Cryan.

"Our findings suggest that coffee, whether caffeinated or decaffeinated, can influence health in distinct but complementary ways."

The research rests on several associations between changes in gut microbes and shifts in mood and behaviour. It also depends on participants' self-reported moods and behaviours, which may not accurately represent reality.

Even so, the study used detailed research comparing the ways participants processed coffee compounds and connecting those variations with metabolic patterns in their gut microbiome.

This provides stronger evidence that coffee may do more than simply correlate with health benefits; it could help shape them.

Limits and future coffee research

Nevertheless, proving this conclusively is challenging, given how little is known about the gut microbiome, its effects on the brain and the way coffee is processed in the gut.

"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," says Cryan.

Considerably more research is needed, but the findings contribute to mounting evidence that coffee may benefit the body and mind in some respects, being associated with lower stress, better mood and potentially reduced symptoms of depression.

Some studies also suggest that decaffeinated coffee can enhance cognitive function.

This latest research again indicates that caffeinated and decaffeinated coffee may each bring physiological and psychological advantages and disadvantages. These should be considered differently by each person according to what they want from coffee.

"The study's comprehensive insights pave the way for future investigations harnessing these interactions for potential health interventions," the research team concludes, "and underscore the importance of understanding coffee's multifaceted effects on human physiology."

The study was published in Nature Communications.