Your daily coffee may be doing more than keeping you awake — scientists found a surprising link between your gut, brain and coffee habit

For many people, coffee is a morning ritual built around one familiar effect: feeling more awake. But new research suggests the drink may be doing more inside the body than simply delivering a caffeine boost.

A study conducted by scientists on individuals who regularly consume coffee has been associated with changes related to the gut-brain axis – a bidirectional interaction between the brain and digestive system.

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This study was published in Nature Communications and included 62 individuals – regular coffee consumers and those who did not regularly consume coffee.

Scientists assessed changes in mood, attention, memory, gut microbes, and biological indicators in response to abstinence from coffee intake and consumption of caffeinated and decaffeinated coffee.

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The findings provide yet another piece of information about the reasons behind the effect of coffee beyond increased alertness. However, the study sample was small and does not allow concluding prevention of depression or memory improvement.

What happened when regular coffee drinkers stopped?

The researchers recruited 31 regular coffee drinkers and 31 people who did not regularly consume coffee. The regular coffee group typically drank three to five cups a day.

The coffee drinkers were asked to give up coffee for two weeks.

During this time, psychologists conducted their tests again, taking samples of their stools and urine for bodily changes. The subjects were given coffee, but they did not know whether the coffee had caffeine or not.That setup allowed researchers to look beyond the obvious question of what caffeine does.

Both caffeinated and decaffeinated coffee consumption was linked with decreased perceived stress, depression, and impulsiveness. In addition, the group that consumed decaffeinated coffee had better results in learning and memory tests.

Caffeinated coffee, meanwhile, was associated with lower anxiety and better vigilance and attention. Researchers also observed links with reduced inflammation.

The findings suggest that caffeine may account for some effects of coffee, but it cannot explain everything researchers observed.

Your gut may be part of the coffee story

One of the more interesting findings involved the communities of microorganisms living in the participants' digestive systems.

Researchers detected changes in several groups of gut bacteria after coffee consumption, including Eggertella sp., Cryptobacterium curtum and members of the Firmicutes group.

That matters because the gut and brain are not isolated systems.

These signals may be communicated through immune reactions, hormones, neural circuits, and metabolic products from the digestion of substances found in drinks by the gut microbes.

Coffee contains many chemical compounds such as polyphenols that can interact with the gut microbiota. This gives researchers an explanation for why caffeine is not entirely responsible for all effects of coffee on the body.

The study therefore adds to research into the microbiota-gut-brain axis — but it does not show that a particular change in gut bacteria directly caused a change in mood or memory.

Decaf produced a result scientists could not ignore

Caffeine is the ingredient most people associate with coffee's effects. It stimulates the nervous system and can increase alertness, which makes it an obvious explanation for feeling more awake after a cup.

But the findings involving decaf make the picture less straightforward.

Participants who consumed decaffeinated coffee showed improvements in learning and memory measures, while both coffee types were associated with changes in perceived stress, depression and impulsivity.

That does not mean decaf is a brain-enhancing drink, or that it will produce the same effects in everyone.

This study was investigating short-term reactions within a controlled environment, not any long-term disease results.

In addition, this study was being conducted with the sponsorship of the Institute for Scientific Information on Coffee (ISIC). This is an organisation backed by coffee companies, which does not discredit the study, but is useful information when assessing it.

From a consumer’s perspective, the most important lesson from this study is that coffee’s biological effects could depend on more than just one compound within coffee.

What this study means for your morning cup

The research adds to evidence that coffee interacts with the body in several ways at once. Its effects may involve the nervous system, gut microorganisms, immune signalling and metabolites produced during digestion.

But there is an important distinction between finding a biological association and proving a health benefit.

This study involved only 62 participants and followed them over a relatively short period. Researchers also cannot use these results to establish that drinking coffee prevents depression, protects memory or reduces the risk of disease.

For someone who already enjoys coffee, the findings provide an interesting reason to look beyond caffeine when considering what happens after that morning cup. They also raise a bigger scientific question: could some of coffee's effects be coming from the interaction between its many compounds and the microbes in the gut?

Answering that will require larger and longer studies.

FAQ

1. Does coffee affect the gut and brain?
The study found changes in gut bacteria and several psychological measures following coffee consumption.

2. Does decaf coffee have effects similar to caffeinated coffee?
Some effects were observed with both types.

3. Does this research show that coffee has any effect on improving memory or preventing depression?

No, it doesn’t, since the research is quite limited in scope and duration, so it only provides some connections.

4. Why might coffee affect the gut?
Coffee has several thousand compounds, among which polyphenols can be mentioned. The interaction of these polyphenols can occur through gut microbiota, which is able to form metabolites for signalling.