Although it wasn’t ‘proven’ in the way we test theories these days, scientists had a ‘gut feeling’, if you like, about the link between the gut and brain for millennia. In this blog post I dig into the gut and find a lot more than I expected.
Main Points:
- We’ve known that the gut and brain are linked for a very long time;
- How they work together has only been recently revealed;
- What we eat in early age sets us with healthy or unhealthy brains;
- We can determine our brain health at any age.
We’ve Known For Two Thousand Years
According to this history of the gut, our ancestors knew there was a link between digestion, mood and behaviour; milk was cited for treating gut problems by Hippocrates around 400 BCE; faecal transplants date back to ~300 BCE in Ancient Greece and ~300 AD in China.
Moving forward to the 19th century, scientists were fascinated by the gut – even calling the stomach ‘the great abdominal brain’. You see, they took for granted that what affected the gut affected the brain and vice versa; they just didn’t know how it worked.
Skipping through to 1904, the idea of the ‘gut-brain axis’ (above) was proposed by Nobel prize-winning scientist Ivan Pavlov. Remember Pavlov’s dog? That was proof that the sight and smell of food triggered gastric juices in the stomach – made the mouth water, if you like – via signals in the brain.
So, we’ve known – intuitively or empirically – that there was a link between our brains and our guts for centuries, but its complexity and elegance have only recently been unravelled.
Human Genome To the Rescue
What saved the gut-brain axis, was the human genome.
More correctly, at the turn of the new millennium, it was the tools created for the Human Genome Project that allowed scientists to see the gut in a new light – and at a new depth.
The miracle of sequencing the human genome – with the promise of finding causative DNA for ailments so we could ‘fix’ them genetically – was marked by the emergence of new technologies that could sequence just about anything.
Fortunately, some scientists were still fascinated by the gut and they let this new technology loose on gut flora – the gut’ microbiome’ we now call it – to see what was down there.
To their astonishment, they found we each have 10-100 trillion beneficial bugs in our guts – that’s over 2,000 different species identified by sequencing – and these tiny microbes drive the gut-brain axis in ways that determine our body and brain health.
...understanding the microbiome will provide exciting prospects for exploiting the microbiota for personalized medicine.
What We Know Now
The number of publications about the gut microbiome has exploded in the past 20 years so I won’t bury you with the details; I’ll cut to the chase.
The Cleveland Clinic has this neat analogy:
‘You can think of your gut microbiome as a thriving native garden that you rely on for nutritious foods and medicines. When your garden is healthy and thriving, you thrive, too. But if the soil is depleted or polluted, or if pests or weeds are overrunning the helpful plants, it can upset your whole ecosystem.’
If you’d like the science, here is some of what the gut microbiome does. It:
- Produces short-chain fatty acids (SCFAs) that produce energy, strengthen the gut and modulate immunity;
- Assists in metabolising fat and balancing cholesterol levels;
- Forms our main line of defence (80% of immune cells are in the gut);
- Fights gut bugs that cause ulcers, gastritis & cancer in the gut;
- Fights toxin-producing bugs that damage nerve cells in the brain;
- Produces neurotransmitters (like serotonin) that drive the gut-brain axis;
- Fights inflammation (linked to auto-immune diseases like arthritis, lupus, psoriasis, and linked to dementia);
- Interacts with the gut lining, the largest endocrine (hormone-producing) system in the body;
- Secretes hormones that regulate blood sugar, hunger and satiety (feeling full).
In short, it’s a pretty spectacular garden which, if nourished properly, will nourish us. If we neglect it, though, it dies and our health declines and so does our brain function.
More on good foods to feed the brain here.
Healthy Gut, Healthy Brain
Clearly, what’s in our guts is vital to our health, which makes sense in a way.
Apart from life-giving oxygen, most of what comes into our bodies is through our mouths – what we eat – so it’s logical that the quality of nutrients we ingest affects everything else. It’s the most basic case of ‘garbage in, garbage out’. The reverse is true too.
This may sound like an abstract argument, but it’s far closer to home. What we eat is doesn’t just affect our heslth, it affects our brains. .
An exhaustive, independent literature study published in April 2026, came to these bald conclusions:
- Signals from our guts are critical regulators of our brain development;
- This impact is felt for our whole lives – early, middle and late;
- Our guts directly affects our brains’ health and vulnerability;
- In early life, healthy guts support brain development and, in older age, brain resilience.
- Disruptions (like antibiotics, poor diet or stress) to gut health early in life can have lifelong consequences;
- Long term impacts include neurodegeneration like Alzheimer’s Diseases and Parkinson’s Disease.
In other words, we need to look after our guts from the cradle to the grave if we want to live and die with healthy brains.
That may sound a bit tough but, in another blog post, I cite the science of diet and how specific foods enfeeble our brains. It’s been known for some time how ‘The Western Diet’, what most people eat in the USA, UK, Canada, Australia and New Zealand, is directly related to neurodegeneration. Is it any wonder that dementia rates are burgeoning in these countries, and not in countries that don’t eat the Western Diet?
Here is more on why the Western Diet is so bad for our brains.
Summing Up
Wanting to finish on a more positive note, our humble guts are more important to the health of our brains and bodies than we thought – and we now know the science behind it. The good news is that the health of our guts and brains is up to us. If we nourish our internal gardens as we do our pot plants and vegies, they will nourish and support us. The choice is up to us.
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Food is one of my passions – I won’t diet for any reason – so I was delighted when I found the link between healthy food and a healthy brain. I was even more excited when I found that healthy food didn’t mean having to eat kale, mung beans or spirulena.
I explore the role of food in protecting the brain – and include some of my favourite recipes – in my eBook Anti-Dementia Food. If you’re a boomer like me who loves food far too much to diet and you want to feed your brain – you may like a peak inside.
ANTI-DEMENTIA FOOD
How you can feed your brain with real food
