All coffee, even decaf, can improve mood, brain health, study finds

Coffee, even decaf, has positive impact on gut-brain axis, a new study has found.

A new study suggests that regularly drinking four cups of coffee a day could have a positive impact on mood and stress levels.
Changes in mood and stress were also associated with changes in gut bacteria and the levels of certain metabolites.
Most of the mood and gut changes occurred alongside drinking both caffeinated and decaffeinated coffee.

Coffee doesn’t just impact your energy levels first thing in the morning; it also influences the makeup of the gut microbiota, which in turn could influence mood and stress levels.

This is according to new research from APC Microbiome Ireland, a research center based at University College Cork, in Ireland. The study is published in Nature Communications.

“Coffee is more than just caffeine,” said study author John Cryan, PhD, Principal Investigator at APC Microbiome Ireland, in a press release. “It’s a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being.”

The term gut microbiota refers to all the different micro-organisms such as bacteria that live inside the digestive tract. They are a vital part of the gut microbiome, which refers not only to the microbes but also the environment they live in.

Research has already established that there is a two-way relationship between the gut and the brain, known as the gut-brain axis. This means that changes in the brain can lead to changes in the gut, and vice versa.

Gut microbiota play a key role within this relationship.

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

Other research has suggested that gut microbes react to coffee, as well as associating different levels of coffee consumption with certain health outcomes. These include reduced risks of some chronic diseases, lower rates of all-cause mortality, and a lower risk of depression.

Researchers have not investigated the effects of coffee drinking and withdrawal over time on drinkers as well as their gut microbiota in depth up until now.

The study began with a comparison of one group of 31 non-coffee drinkers with 31 coffee drinkers. Coffee drinkers were people who regularly consumed between 3 and 5 cups of coffee a day.

With each participant, the researchers assessed several parameters with a range of tests, questionnaires, self reports, and stool and urine samples. These included:

cognitive function
stress levels
physical health
mood
immune function
diet
gut microbiome composition.

After these baseline tests, the non-coffee drinker group played no further part in the study.

The coffee-drinking group then stopped drinking coffee for 14 days, while also abstaining from other sources of caffeine, such as sodas and dark chocolate.

After this time, they reintroduced coffee to their diets. However, half of them (15 people) reintroduced decaffeinated coffee while the other half (16 people) reintroduced caffeinated coffee.

The participants then drank whichever type of coffee the researchers had blindly assigned to them for 21 days. Their instructions were to drink four sachets of instant coffee each day.

The researchers carried out further assessments on this group of participants throughout their period of abstinence from coffee and then again during the 3-week intervention phase.

How coffee reshapes the gut

The researchers found that when participants returned to drinking coffee after the 14-day abstinence period, both caffeinated and decaffeinated coffee were associated with improvements in mood.

The participants’ questionnaires revealed lower levels of stress, depression, and impulsivity after returning to either type of coffee.

Caffeinated coffee alone was associated with reduced anxiety and improved vigilance, attention, and blood pressure. In contrast, decaffeinated coffee was associated with improvements in learning, memory, physical activity, and sleep.

Interestingly, the researchers did not note any differences between the coffee drinkers and the non-coffee drinkers at the start of the study and after the abstinence period when it came to many of these factors. This included blood pressure, stress, anxiety, depression, sleep quality, and physical activity.

Alongside the changes in mood and cognition, the researchers also observed several changes in the guts of the participants.

During the 2-week abstinence period, they noted changes in levels of certain metabolites, which are small molecules that are produced during the process of metabolism.

These levels largely returned after the participants started drinking coffee again, although levels of metabolites closely associated with caffeine did not rise for those drinking decaffeinated coffee.

Overall, the researchers identified nine key metabolites that were closely associated with coffee drinking. These included theophylline, caffeine, and selected phenolic acids, and were “strongly linked to microbial species and cognitive measures.”

There were also clear differences between the gut microbiomes of coffee drinkers compared with nondrinkers. There were higher levels of specific species of bacteria associated with positive health effects in the guts of the coffee drinkers.

These included:

Cryptobacterium curtum, which is associated with oral health
Eggertella sp. CAG:209, which is associated with bile acid synthesis
Firmicutes CAG:94, which is associated with positive emotions in females.

“Our findings suggest that coffee, whether caffeinated or decaffeinated, can influence health in distinct but complementary ways,” said Cryan in the press release.

Medical News Today

Written by: James McIntosh

Fact Checked by: Kevin Cyr, MD

All coffee, even decaf, can improve mood, brain health, study finds