Nature Communications: Decaf Coffee Improved Memory, While Caffeinated Coffee Did Not

The study involved 31 regular coffee drinkers. First, all participants abstained from their usual three to five cups of coffee a day for two weeks. They then drank four servings of instant coffee daily for three weeks: half received decaffeinated coffee and half received caffeinated coffee. Neither the participants nor the researchers knew who was receiving which type. At the end of the study, only those who drank decaf showed a noticeable improvement in memory test results, including word recall and accuracy in identifying the locations of objects.

Both groups experienced reductions in stress, low mood and impulsivity. Caffeinated coffee also reduced anxiety and improved attention. Most importantly, however, coffee altered the composition of the gut microbiota regardless of whether it contained caffeine. According to the authors, polyphenols may be responsible for this effect. These compounds serve as food for beneficial gut microbes, which, through the gut–brain axis, can influence cognitive function and mood without relying on caffeine’s direct effects on the nervous system.

“Coffee is much more than just caffeine. It is a complex dietary factor that interacts with our gut microbes, metabolism and even our emotional state,” Cryan noted. If the findings are confirmed, they could change the conventional view of decaf as an “inferior” substitute. Caffeine-free coffee appears to offer benefits of its own rather than simply lacking the stimulating effects of regular coffee.

The authors, however, urge caution. The study sample was very small, comprising just 31 people, and the observation period lasted only a few weeks. It is therefore too early to draw far-reaching conclusions. The findings will need to be confirmed in larger, more diverse groups, with participants followed over a longer period.