Coffee, including decaffeinated varieties, has the potential to boost mood and cognitive function, according to a recent study.

• A recent investigation indicates that consuming around four cups of coffee daily could positively affect one’s disposition and stress levels.
• Alterations in mood and stress were also correlated with changes in gut bacteria and the concentrations of certain metabolites.
• The majority of mood and gut modifications occurred alongside the consumption of both caffeinated and decaffeinated coffee.

Coffee not only affects your alertness at the start of the day but also influences the composition of your gut microbiota, which consequently could impact mood and stress levels.

This finding emerges from new research conducted by APC Microbiome Ireland, a research institution situated at University College Cork in Ireland. The study has been published in Nature Communications.

“Coffee is more than just caffeine,” stated the study’s author, John Cryan, PhD, a Principal Investigator at APC Microbiome Ireland, in a press release. “It’s a multifaceted dietary component that interacts with our gut microbes, our metabolism, and even our emotional state.”

The term gut microbiota refers to the diverse range of microorganisms, such as bacteria, residing within the digestive tract. These are a crucial part of the gut microbiome, which encompasses not only the microbes themselves but also their living environment.

Previous research has already established a bidirectional connection between the gut and the brain, referred to as the gut-brain axis. This implies that changes occurring in the brain can trigger changes in the gut, and vice versa.

Gut microbiota play a significant role in this interrelationship.

“Public fascination with gut health has seen a tremendous surge,” commented Cryan. “The connection between digestive and mental health is also increasingly being better understood, but the specific mechanisms behind coffee’s influence on this gut-brain axis have remained elusive.”

Other investigations have suggested that gut microbes respond to coffee and have associated varying levels of coffee intake with particular health outcomes. These include diminished risks of certain chronic conditions, lower rates of mortality from all causes, and a reduced likelihood of developing depression.

To date, researchers have not extensively examined the effects of coffee consumption and subsequent withdrawal over time on both drinkers and their gut microbiota.

How did the study assess the effects of coffee intake?

The study commenced with a comparative analysis involving one group of 31 individuals who did not consume coffee and 31 individuals who did. The coffee drinkers were participants who habitually consumed between 3 and 5 cups of coffee daily.

For each participant, the researchers evaluated several parameters using a variety of tests, questionnaires, self-assessments, and stool and urine samples. These included:

• cognitive performance
• stress levels
• physical well-being
• mood
• immune system function
• dietary habits
• gut microbiome composition.

Following these initial baseline assessments, the non-coffee-drinking group did not participate further in the study.

The group of coffee drinkers then abstained from coffee for 14 days, concurrently avoiding other sources of caffeine, such as sodas and dark chocolate.

After this period, they reintroduced coffee into their diets. However, half of them (15 individuals) reintroduced decaffeinated coffee, while the other half (16 individuals) reintroduced caffeinated coffee.

The participants then consumed whichever type of coffee the researchers had assigned to them blindly for 21 days. Their instruction was to consume four sachets of instant coffee each day.

The researchers conducted further evaluations on this participant group during their period of coffee abstinence and again during the 3-week intervention phase.

How coffee reshapes the gut

The researchers discovered that when participants resumed drinking coffee following the 14-day abstinence period, both caffeinated and decaffeinated coffee were associated with mood enhancements.

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

Only caffeinated coffee was linked to diminished anxiety and improved alertness, concentration, and blood pressure. Conversely, decaffeinated coffee was associated with advancements in learning, memory, physical activity, and sleep.

Notably, the researchers did not observe any significant differences between the coffee drinkers and non-coffee drinkers at the commencement of the study and after the abstinence period concerning many of these aspects. This included blood pressure, stress, anxiety, depression, sleep quality, and physical activity.

In addition to the changes in mood and cognition, the researchers also identified several alterations within the participants’ digestive systems.

During the 2-week abstinence phase, they noted changes in the concentrations of specific metabolites, which are small molecules generated through the metabolic process.

These levels largely normalized after participants recommenced coffee consumption, although the concentrations of metabolites closely linked to caffeine did not increase in those consuming decaffeinated coffee.

Collectively, the researchers identified nine crucial metabolites strongly associated with coffee consumption. These included theophylline, caffeine, and selected phenolic acids, and were “strongly linked to microbial species and cognitive measures.”

Significant distinctions were also evident between the gut microbiomes of coffee drinkers and non-drinkers. Higher proportions of specific bacterial species linked to beneficial health effects were found in the guts of coffee drinkers.

These included:

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

“Our findings suggest that coffee, irrespective of whether it is caffeinated or decaffeinated, can positively influence health through distinct yet complementary pathways,” stated Cryan in the press release.

Only caffeinated coffee linked to lower anxiety

“Our discoveries shed light on the microbiome and neurological responses to coffee, as well as their potential long-term advantages for a healthier microbiome,” said Cryan in the press release. “Coffee may alter the collective actions of microbes and the metabolites they utilize.”

Medical News Today inquired with Cryan whether the observed reduction in stress and depression among coffee drinkers after resuming their habit might be attributed to the psychological effect of returning to a routine rather than a direct consequence of the coffee itself.

Cryan informed us that the return to a habitual behavior can indeed yield psychological benefits, such as reduced stress and improved mood, but that the study was designed to account for this.

“We included both caffeinated and decaffeinated coffee, and both groups exhibited improvements in stress and depression. This indicates that non-caffeine factors, including psychological or behavioral influences, might play a role,” he remarked.

“However, only caffeinated coffee led to a reduction in anxiety and psychological distress, suggesting that caffeine-specific biological effects are also involved,“ he added.

“Taken together, the findings suggest that the observed benefits are likely due to a combination of factors, biological effects of coffee compounds — including caffeine and (poly)phenols — microbiome-mediated mechanisms, and psychological effects linked to routine and expectation.”

– John Cryan, PhD

While these preliminary findings are intriguing, it is crucial to acknowledge that the study was relatively small, involving data from only 62 participants. Furthermore, the researchers did not analyze differences based on ethnicity, as the majority of the participants were Caucasian.

The study also exclusively examined the effects of instant coffee. MNT posed a question to Cryan regarding whether different coffee varieties or preparation methods might yield dissimilar outcomes.

“Varying coffee types and preparation techniques can substantially alter the chemical makeup of the final beverage,” he stated. “The brewing method impacts the levels of caffeine, (poly)phenols, and other biologically active compounds such as diterpenes and chlorogenic acids.

“In our study, we concentrated on controlled interventions using standardized caffeinated and decaffeinated coffee to isolate biological effects. However, instant coffee might differ from freshly brewed coffee in its polyphenol profile and processing-related compounds, which could affect its interaction with the gut microbiome and metabolism,” Cryan elaborated.

“While we anticipate generally similar directional effects across different coffee types, the magnitude and specific microbial or metabolic responses may fluctuate depending on the preparation method,” he continued. “This represents a significant area for future inquiry, particularly within the context of personalized nutrition and microbiome reactions.”

For the present, however, this study offers additional understanding into the complexities of the gut microbiome and the potential role that one of the world’s most beloved beverages may play in maintaining health.

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