Decaf coffee may boost memory, while caffeine could help ease anxiety: Study

Coffee is often the first drink of the day for millions of people, but new research suggests that its effects may extend well beyond helping us wake up.

A study by researchers at APC Microbiome Ireland at University College Cork has examined how caffeinated and decaffeinated coffee affect the gut microbiome and the gut-brain axis — the communication network linking the digestive system and the brain.

Published in Nature Communications, the research found that coffee consumption was associated with changes in gut microbes and metabolites, with caffeinated and decaffeinated coffee showing some distinct effects on mood and cognitive performance.

WHAT DID THE STUDY FIND?

The study involved 62 participants, including regular coffee drinkers and people who did not consume coffee.

The regular coffee drinkers typically consumed three to five cups a day, an amount considered safe and moderate for most adults by the European Food Safety Authority.

Researchers first asked the regular coffee drinkers to avoid coffee for two weeks. During this period, they assessed participants’ psychological wellbeing and collected stool and urine samples to monitor changes in gut bacteria and metabolites.

When coffee was reintroduced, participants were unknowingly given either caffeinated or decaffeinated coffee.

Both groups reported reductions in perceived stress, depression and impulsivity after returning to coffee. The finding suggests that caffeine may not be responsible for all of coffee’s potential effects on mood.

DECAF LINKED TO MEMORY, CAFFEINE TO ALERTNESS

Researchers also identified differences in the gut microbiomes of coffee drinkers and non-drinkers.

Eggertella species and Cryptobacterium curtum were found at higher levels among coffee drinkers. These bacteria have been linked to processes involving intestinal acid secretion and bile acid metabolism.

The study also found higher levels of Firmicutes bacteria among coffee consumers. Earlier research has associated some members of this bacterial group with positive emotions in women.

The researchers found differences between the two types of coffee when it came to cognitive effects.

Participants drinking decaffeinated coffee showed improvements in learning and memory, while those consuming caffeinated coffee reported lower anxiety and showed improvements in vigilance and attention.

Caffeinated coffee was also associated with a lower risk of inflammation in the study.

‘COFFEE IS MORE THAN JUST CAFFEINE’

Professor John Cryan, Principal Investigator at APC Microbiome Ireland and the study’s corresponding author, said the findings provide new insight into coffee’s relationship with the gut-brain axis.

“Public interest in gut health has risen hugely. 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,” Cryan said.

He added that coffee may influence the collective activity of gut microbes and the metabolites they produce, potentially contributing to its effects on health.

“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,” Cryan said.

The researchers concluded that caffeinated and decaffeinated coffee may affect the body through different but overlapping pathways. However, the study’s relatively small sample size means larger studies will be needed to determine whether these findings translate into longer-term health benefits.