A new study suggests coffee affects the brain and body through more than just caffeine, with both regular and decaffeinated versions showing benefits for mood, memory, and stress levels.
Researchers conducted a randomized crossover trial, a method where the same participants are tested under different conditions, allowing each person to serve as their own control. The study involved healthy adults and tracked them through three phases: a period of regular coffee consumption, a washout phase without coffee, and a reintroduction phase with either caffeinated or decaffeinated coffee.
During the study, participants completed cognitive tasks measuring attention, memory, and mental flexibility. They also reported on mood, stress, and emotional reactivity. Researchers analyzed the gut microbiome using advanced sequencing and tracked metabolites, small molecules produced during digestion that can influence brain function.
The goal was to understand how coffee might work through the gut-brain axis, the communication network linking the digestive system and the brain.
Both Regular and Decaf Coffee Show Effects
When participants reintroduced coffee after the washout period, both caffeinated and decaffeinated versions led to improvements in mood. People reported lower stress, fewer symptoms of depression, and less impulsivity. This suggests caffeine is not the only factor involved.
Caffeinated coffee had some unique effects. It was more strongly linked to reduced anxiety and better attention and vigilance, consistent with caffeine’s role as a stimulant. Decaf was associated with better sleep, improved memory and learning, and higher levels of physical activity.
Instead of a single effect, coffee appears to do multiple things at once, depending on its composition and how the body responds.
Coffee and Gut Health
Coffee intake changed the composition of the gut microbiome, increasing certain bacterial species and shifting the production of metabolites linked to brain health and inflammation. Some of these compounds are involved in regulating mood and cognitive function, which helps explain why effects appeared even without caffeine.
This happens through the gut-brain axis. Microbes in the gut help produce and regulate neurotransmitters, immune signals, and metabolic compounds the brain relies on. When coffee changes that environment, it can indirectly shape how a person feels and thinks.
The Takeaway
This research broadens the understanding of what coffee does. It is not just a stimulant. It is a complex mix of compounds, including polyphenols, plant-based molecules that can act as fuel for beneficial gut bacteria. These downstream effects may be part of why coffee has been linked to better long-term brain and metabolic health.
The findings also take some pressure off caffeine itself. For people sensitive to caffeine or trying to cut back, decaf is not a downgrade as often assumed. It still provides many of the same gut and mood-related benefits, just without the stimulant effect.
