Can Your Gut Microbiome Change Your Brain?
TL;DR: A landmark study found changing the gut microbiome altered brain chemistry and behaviour in mice. Researchers showed that gut bacteria influenced levels of brain-derived neurotrophic factor (BDNF), a protein involved in learning, memory and brain health.
Gut Brain Axis
Most people still think of the gut as a digestive organ.
It breaks down food, absorbs nutrients and gets rid of waste.
But over the past two decades, scientists have discovered that the gut also communicates with the brain (there is some evidence gut health might be connected to ADHD).
This communication network is now known as the gut-brain axis, and one of the studies that helped put it on the scientific map was published in Gastroenterology in 2011.
The findings were remarkable.
Researchers changed the gut bacteria in healthy mice and observed changes not only in their behaviour, but also in their brain chemistry.
What Did the Researchers Do?
The researchers wanted to answer a simple question:
Can changing the gut microbiome change the brain?
To find out, they temporarily altered the gut bacteria of healthy mice using a combination of non-absorbed antibiotics.
Because these antibiotics remain largely within the digestive tract, the researchers could investigate whether changes in the gut microbiome alone influenced the brain.
They also performed a second experiment using germ-free mice, which are raised without any gut bacteria.
These mice were then colonised with gut bacteria from different strains of mice that naturally displayed different behaviours.
Results... Surprising!
The mice with altered gut bacteria became noticeably more exploratory.
They were less hesitant to explore unfamiliar environments and displayed behaviours that suggested reduced anxiety compared with the control mice.
Even more interesting was what happened inside the brain.
The researchers found significantly higher levels of brain-derived neurotrophic factor (BDNF) in the hippocampus, an area of the brain involved in learning, memory and neuro-plasticity.
When the gut microbiome returned to normal, the behavioural changes disappeared.
This suggested that the gut bacteria themselves were influencing brain function rather than causing permanent changes.
The Gut Microbiome Even Transferred Behaviour
Perhaps the most fascinating part of the study involved the germ-free mice.
Researchers transferred gut bacteria from naturally adventurous mice into timid mice.
The timid mice became significantly more exploratory.
When they transferred bacteria from timid mice into naturally adventurous mice, the opposite happened.
The recipient mice became more cautious.
This showed that altering the gut microbiome could influence behaviour, independent of genetics.
Why This Study Was So Important
The researchers carefully investigated whether something else could explain the results.
They found the behavioural changes were not associated with:
- Gut inflammation
- Changes in gut serotonin
- Changes in dopamine or noradrenaline
- The vagus nerve
- The sympathetic nervous system
Instead, the evidence suggested that the gut microbiome itself was influencing brain chemistry through mechanisms that were not yet fully understood.
At the time, this was a major shift in how scientists thought about the relationship between the gut and the brain.
What Is BDNF?
Brain-derived neurotrophic factor, or BDNF, is sometimes described as "fertiliser for the brain."
It helps nerve cells survive, grow and communicate with one another. BDNF is involved in learning, memory and the brain's ability to adapt and form new connections.
The finding that changing gut bacteria altered BDNF levels suggested that the microbiome may influence much more than digestion.
What Does This Mean for You?
Let's keep this study in perspective.
These experiments were performed in mice, not humans.
However, they do raise an interesting possibility.
If you've been struggling with low motivation, brain fog, poor concentration or simply don't feel your best, your gut health may be one area worth exploring alongside other aspects of your lifestyle, such as sleep, nutrition, exercise and stress management.
We already know that a healthy gut microbiome supports digestion and immune function.
Research like this suggests it may also influence how the brain functions, although much more human research is still needed before firm conclusions can be drawn.
One thing is becoming increasingly clear: looking after your gut isn't just about reducing bloating or improving digestion. It may also be an investment in your long-term brain health.
Supporting a Healthy Gut Microbiome
While there is still much to learn, we already know that a healthy gut microbiome is supported by:
- Eating a wide variety of plant foods
- Consuming adequate dietary fibre
- Staying physically active
- Getting enough sleep
- Managing stress
Prebiotic fibres are particularly interesting because they feed beneficial gut bacteria rather than introducing new bacteria into the gut.
One of the most researched prebiotic fibres is PHGG powder, which has been studied for its ability to support beneficial gut bacteria, digestive health and bowel regularity.
Final Thoughts
This landmark study helped change the way scientists think about the gut-brain axis.
Rather than acting independently, the digestive system and the brain appear to communicate constantly through a complex network involving the gut microbiome.
Although much of the current evidence is still emerging, one message is becoming increasingly clear.
Looking after your gut may benefit far more than your digestion.
Reference
Bercik P, Denou E, Collins J, et al. The intestinal microbiota affect central levels of brain-derived neurotropic factor and behavior in mice. Gastroenterology. 2011;141(2):599-609.e3. doi:10.1053/j.gastro.2011.04.052
About the Author
Grant Jenkins is the founder of Propel Health Australia and a physiologist with more than 25 years of experience in sports nutrition, exercise physiology and evidence-based supplementation. He translates emerging scientific research into practical health information to help Australians make informed decisions about nutrition and wellbeing.
Disclaimer
This article is intended for educational purposes only and is not medical advice. Always consult your healthcare practitioner before making changes to your diet, supplements or healthcare routine.
