Ever had “butterflies in the stomach” before an important presentation?
Felt your stomach twist into knots during an argument?
Or suddenly needed the toilet five minutes before an exam, interview or first date?
Congratulations, your gut and brain have been gossiping about you behind your back.
For years, people assumed emotions came only from the brain.
But scientists now know that the gut and brain are in constant communication through a network known as the gut-brain axis.
This is a two-way communication system involving nerves, hormones, immune signals, and perhaps most surprisingly, trillions of bacteria living inside our intestines.
Yes, the tiny microbes in your gut may be influencing far more than your digestion.
Those helpful roommates
Your intestines are home to trillions of bacteria and other microorganisms, which are collectively known as the gut microbiome.
While this may sound alarming, most of these microbes are actually helpful roommates.
They help digest food, produce vitamins, regulate inflammation, support immunity and communicate with the nervous system.
In return, all they ask for is some fibre and decent treatment.
Unfortunately, many of us are feeding ourselves while quietly starving our microbes.
Modern lifestyles are not exactly microbial paradise.
Fast food, ultra-processed snacks, sugary drinks, irregular meals, chronic stress and poor sleep are becoming increasingly common, especially among busy Malaysians juggling work, traffic, deadlines and social media-fuelled stress.
Our gut bacteria are probably stressed and exhausted too.
Our ‘second brain’
Scientists sometimes refer to the gut as the “second brain”.
This is not because there is an actual brain in the abdomen, but because the digestive system contains an enormous network of nerves known as the enteric nervous system.
This network constantly exchanges signals with the brain.
In fact, up to 90% of the body’s serotonin – a chemical involved in mood regulation – is produced in the gut.
This does not mean that your stomach has feelings or your bacteria are secretly controlling your life choices.
Your microbes are probably not responsible for that midnight online shopping spree or your decision to drink a fourth cup of coffee at 10pm.
However, growing research suggests that gut microbes may influence how the body responds to stress, inflammation and emotional regulation.
Research published in the journal Nature Reviews Microbiology in 2023 highlighted how gut microbes communicate with the brain through chemical, immune and nerve pathways.
Another study published in the journal Nature Mental Health in 2024 found associations between certain gut microbiome patterns and depressive symptoms.
Scientists are still learning exactly how strong these connections are, but the evidence supporting the gut–brain axis continues to grow rapidly.
Stress and your gut
Stress itself can disrupt the gut microbiome, creating a biological loop.
Stress changes the gut environment, and an unhealthy gut may in turn worsen stress responses.
It is essentially an argument between the brain and the intestines, with neither side wanting to give in.
Many people notice this connection in daily life without realising it.
Some lose their appetite when anxious.
Others stress-eat an entire packet of chips while promising themselves it is “just one bad day”.
Some experience bloating, stomach discomfort or diarrhoea during emotionally difficult periods.
The gut is not simply digesting food; it is processing your emotions.
Beyond diet
Sleep also matters.
Studies suggest that poor sleep patterns can disrupt the microbiome, while exercise appears to improve bacterial diversity.
Even spending time outdoors and reducing stress may positively influence gut health.
Your microbes are surprisingly sensitive little creatures.
Of course, it is important not to oversimplify things.
Depression, anxiety and mental health disorders are complex conditions involving genetics, environment, psychology and biology.
Gut bacteria are only one piece of a much larger puzzle.
Eating yoghurt alone will not solve emotional distress, and probiotics are not magical happiness pills.
However, maintaining a healthy gut may be one useful way to support overall well-being, alongside proper medical care, healthy lifestyle habits and emotional support.
Perhaps the most fascinating part of all this is the realisation that humans are not functioning alone.
We are ecosystems.
Inside every person is a bustling microscopic city of organisms interacting with our immune system, digestion, metabolism, and possibly even aspects of mood and behaviour.
So, the next time stress makes your stomach churn, remember that your gut and brain are probably having a very intense discussion.
Dr Vinoth Kumarasamy is a parasitologist and lecturer at Universiti Kebangsaan Malaysia. For more information, email starhealth@thestar.com.my. The information provided is for educational and communication purposes only, and should not be considered as medical advice. The Star does not give any warranty on accuracy, complete-ness, functionality, usefulness or other assurances as to the con-tent appearing in this article. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
