The Gut- Brain Connection: How can gut health support your mood?
When we think about mental health, we naturally think about the brain. But brain health does not exist in isolation. Our brain is closely connected to the rest of our body - including our immune system, nervous system and our gut.
And whilst so many factors can impact our mental health status at any one time - genetics, early life experiences, exercise, stress, sleep, environment (to name a few) - diet is one of the evidence-based factors in our control that we can focus on. The quality of our diet can contribute to better mental wellbeing.
Your gut and brain are in constant communication
Let’s take a closer look at our gut. Your gut isn't simply a digestive system processing and absorbing food. It contains a complex nervous system, alongside trillions of microorganisms that make up your gut microbiome. Together, these systems communicate continuously with the brain through what's known as the gut-brain axis.
And importantly, this relationship is bidirectional - it works both ways.
In other words:
Stress → brain → changes in gut function
but also:
Diet/gut microbes/gut signals → nervous system → brain
This helps explain why you might experience a "gut feeling" or “butterflies in your stomach” when you're nervous. These sensations have a physiological basis.
It also helps explain why digestive symptoms such as bloating, constipation and diarrhoea can commonly occur alongside anxiety and low mood. The gut and brain influence one another, rather than functioning as two completely separate systems.
The upstairs and downstairs analogy - Downton Abbey
I like to think of the gut and brain as the upstairs and downstairs of a large house - a little like Downton Abbey! The brain is upstairs and the gut is downstairs.
Although they have different jobs, they depend on one another. What happens downstairs can affect upstairs, and what happens upstairs can affect downstairs.
For example, psychological stress can alter gut function. Equally, signals originating in the gut can influence the nervous system, immune responses and stress pathways.
So when we're talking about brain health, mood and mental wellbeing, we need to include our gut firmly in that same conversation.
Meet your gut microbiome: A diverse rainforest
I like to think of our gut bacteria or gut microbiome as a rainforest: diverse, dynamic and constantly interacting with its environment. It is a complex ecosystem containing trillions of microorganisms.
One of the important characteristics of a healthy microbiome is diversity. Our gut microbes help us process components of food that we can't fully digest ourselves. In particular, fibre provides fuel for many beneficial microbes, allowing them to produce beneficial compounds that can support the gut lining and interact with immune and metabolic processes.
The microbiome also communicates with our nervous system and can influence pathways involved in stress, metabolism and brain function.
Research has found differences in gut microbial composition and diversity in people experiencing conditions such as anxiety and depression. Your microbes are even involved in dopamine levels - they tweak pathways in our brain (via the gut - brain axis) that help to light up specific regions of pleasure, happiness, enjoyment and comfort.
What about our happy hormone, serotonin?
You may have heard that most of the body's serotonin is found in the gut rather than the brain.
This is true, but it needs a little explanation.
Serotonin has important functions within the gastrointestinal tract, and gut microbes can influence pathways involved in serotonin and tryptophan metabolism. However, serotonin produced in the gut doesn't simply travel across into the brain. The brain regulates its own serotonin system separately.
What we eat can nevertheless provide the nutrients and building blocks involved in neurotransmitter production and normal nervous-system function.
This is another reason why overall nutritional adequacy and dietary quality matter.
So, can changing your diet improve your gut microbiome?
The encouraging news is that our gut health and microbiome are responsive to dietary change, and research suggests that dietary changes can produce measurable changes, specifically in the gut microbiota, within as little as a few weeks.
But this doesn't mean we need a complicated diet, expensive supplements or a cupboard full of probiotic products.
Instead, think variety.
Feed your microbiome
One of the simplest ways to support your gut microbes is to provide plenty of different types of plant foods.
A useful target is 30+ different plant foods per week, including:
Fruit and vegetables
Wholegrains
Beans and pulses
Nuts and seeds
Herbs and spices
The aim isn't perfection. It's simply to start introducing more variety and build on this over time.
Think about eating a rainbow of plant foods rather than eating the same few foods every day.
What about “superfoods”, probiotics and supplements?
Probiotic supplements can be useful in certain circumstances, and research into specific probiotic strains is ongoing. However, supplements aren't essential for everyone and there isn't one probiotic that is right for everybody.
It's also important to remember that probiotics aren't a substitute for fibre.
Your existing gut microbes need food too!
This is why a dietary pattern that combines fibre-rich plant foods with a variety of fermented foods, where tolerated, can be a useful approach.
Rather than focusing on individual "superfoods", think about the overall pattern of your diet.
Food is more than an isolated nutrient. The food matrix - the combination of nutrients, fibre and other compounds naturally present in whole foods - matters.
The bigger picture
Perhaps the most important message is that gut health isn't something we need to "fix" with extreme diets or restrictive eating.
Our gut is a living ecosystem that responds to what we eat and how we live.
Supporting it is much more about consistency than perfection.
Your gut and your brain are constantly communicating. Looking after one is part of looking after the other.