Researchers link coffee to brain health by changing the gut microbiome

A clinical trial by APC Microbiome Ireland, the research center at University College Cork, uncovers how regular consumption of both caffeinated and decaffeinated coffee can affect the gut microbiome, which in turn may influence mood and stress levels. Specifically, the study reports that drinking coffee significantly improved mood, regardless of caffeine content, and links caffeinated coffee to reduced feelings of anxiety and improved focus. 

The authors note is the first trail that explores the nuanced mechanisms behind coffee’s benefits on the gut-brain axis. They underscore that, to date, coffee’s benefits for both digestion and mood have been widely studied, but the exact mechanisms behind these effects have remained unclear.

“Coffee is more than just caffeine — it’s a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being,” says co-author of the study John Cryan, professor and principal investigator at APC Microbiome Ireland.

“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,” he notes. “Our findings suggest that coffee, whether caffeinated or decaffeinated, can influence health in distinct but complementary ways.”

Delving into the gut-brain axis

The study is published in Nature Communications and sponsored by the Institute for Scientific Information on Coffee. It investigated the bidirectional communication between the gut microbiome and the brain through a wide range of measures. 

Participants in the trial consisted of 31 coffee drinkers and 31 non-coffee drinkers who were closely studied through a series of psychological tests, caffeine intake monitoring, and food diaries.

“Coffee drinkers” were identified as participants who regularly consume three to five cups of coffee each day, which is defined by the European Food Safety Authority as a safe and moderate amount for most consumers.

All participants first abstained from coffee for a washout period of two weeks, while completing their regular psychological assessments. Stool and urine samples provided insights into changes in their microbiome, while the participants reported on perceived mood or stress levels.

The abstinence period for coffee-drinkers corresponded with significant changes in metabolite profiles in the gut microbiome, compared to non-coffee drinkers.

Feeding bacteria

Coffee was reintroduced to regular drinkers on a blinded basis, with half of the participants consuming decaffeinated coffee and the other half caffeinated coffee. Both groups reported lower perceived stress, depression, and impulsivity scores, suggesting that drinking coffee significantly improved mood, regardless of caffeine content.

Bacteria, such as Eggertella sp or Cryptobacterium curtum, notably increased in coffee drinkers compared to non-coffee drinkers, the researchers found.

They attribute Eggertella to playing a role in gastric and intestinal acid secretion. Meanwhile, C. curtum is believed to be involved in bile acid synthesis. Both bacteria may play a role in eliminating unhealthy gut bacteria and stomach infections, note the scientists. 

Levels of Firmicutes bacteria also increased, which have been associated with positive emotions in females.

A notable improvement in learning and memory was found only in those who consumed decaffeinated coffee, suggesting that components other than caffeine, such as polyphenols, are responsible for these cognitive benefits.

However, in this study, the researchers found that only caffeinated coffee was associated with reduced feelings of anxiety, as well as improved vigilance and attention. Caffeine was also linked to a reduced risk of inflammation.

“Our findings reveal the microbiome and neurological responses to coffee, as well as their potential long-term benefits for a healthier microbiome. Coffee may modify what microbes do collectively, and what metabolites they use,” says Cryan.

“As the public continues to think about dietary changes for the right digestive balance, coffee has the potential to also be harnessed as a further intervention as part of a healthy, balanced diet.”

Science illuminates coffee’s health halo

Coffee’s reputation in health research is positively represented. One recent trial found that drinking two to three cups daily may reduce dementia risk, slow down cognitive decline, and preserve cognitive abilities. This study had a follow-up of up to 43 years and demonstrates that daily coffee consumption could have long-term protective benefits for the brain.

New hot beverage formulations introduced this year are also exploring how to stack additional benefits on top of the morning drink. Last month, Bulletproof launched Coffee + Creatine, a “first of its kind” functional coffee innovation featuring creatine monohydrate and 250 mg of electrolytes to support performance and hydration.