From gut feelings to cancer clues: the gut-brain connection

When we think about gut health, we often focus on digestion. But there’s much more happening beneath the surface. Deep within your body, a conversation is taking place between your gut and brain. This two-way communication system, known as the gut-brain axis, allows these organs to share information through a network of nerves, hormones, immune signals, and trillions of gut microbes (bacteria)¹.

At the heart of this connection is the gut microbiome – a bustling community of microorganisms that supports digestion while also playing a broader health role¹. When this delicate ecosystem is in balance, it helps maintain overall wellbeing. However, when homeostasis (a state of stability within the gut's microbial ecosystem) is disturbed, the ripple effects of this can contribute to a range of health issues, including gastrointestinal (GI) cancers², which are among the most common cancers affecting Australians³.

How your gut talks to your brain, and why it matters

Your body hosts around 100 trillion bacteria, and most of them live in your gut. These tiny microbes don’t just help with digestion – they also play a big role in how your gut and brain communicate¹.

The gut-brain axis links your gut microbiome with your brain and nervous system. Through this network, gut microbes send and receive signals that influence digestion, mood and immunity⁴.

Here’s how your gut and brain stay in touch^1,4: 

• Nerve signals: Your gut and brain talk to each other through nerves. Some gut bacteria can affect how these messages are sent and even help produce brain chemicals like serotonin, which influence mood and digestion.
• Hormones: Gut microbes help control hormones that manage stress, hunger, energy and emotions – like cortisol, ghrelin and leptin.
• Immune signals: Your gut bacteria also help regulate your immune system and inflammation throughout the body.

When your gut is healthy and has a good mix of microbes, this communication works well. But factors like poor diet, stress, illness or certain medications can throw it off, which may lead to digestive issues, inflammation and other health problems down the track⁵.

Problems often start when there’s too much of one type of bacteria, not enough of the helpful ones, or less variety overall^1,2,5,6. These imbalances can cause inflammation in the gut and throughout the body, which can lead to health issues^1,6.

Gut microbes and GI cancer – what the science says

Researchers are discovering that the gut, brain and the microbes in your digestive system may play a role in how some GI cancers start and grow⁷.

Signals from cancer cells can reach the brain through nerves and the immune system, and the brain can send signals back that may affect how those tumours behave⁷.

An unhealthy gut microbiome can also trigger inflammation, which may increase the risk of cancer. Some harmful bacteria may even help cancer cells grow. For example, Helicobacter pylori (H. pylori) – a common gut bug – is known to cause stomach cancer by creating long-term inflammation that damages tissue. Other gut bacteria may also be linked to colorectal and pancreatic cancers⁵. 

Support your gut, protect your health

While some risk factors for gut health and cancer are out of your control, there’s a lot you can do to support a healthy microbiome and strengthen the gut-brain connection.

Eat more plant-based foods

What you put on your plate has the biggest impact on your gut bacteria. Diets rich in vegetables, fruit and other plant-based foods (especially those high in fibre) help your gut microbiome stay healthy and diverse. Studies also show that people who eat mostly plant-based diets, like vegans and vegetarians, tend to have more diverse gut bacteria than those who eat more meat⁵.

Manage stress

Stress hormones can disrupt your gut microbes and communication along the gut-brain axis⁵. Practising mindfulness and other relaxation techniques can help manage stress, therefore helping to protect your gut and overall wellbeing.

Use antibiotics wisely

Antibiotics can be lifesaving, but they don’t just kill the harmful bacteria – they can also wipe out the beneficial bacteria in your gut. This can lead to a less diverse microbiome, and in some cases, these bacteria never return⁵. It’s important to use antibiotics only when necessary, and always with the advice of your doctor.

Stay active

Exercise has been shown to increase the diversity of gut bacteria, which is linked to better digestion and overall health⁵.

Evidence-based ways to nurture your gut microbiome

Here are some simple, evidence-based strategies you can incorporate into your daily routine.

Increase your dietary fibre

Fibre and gut health go hand in hand. A fibre-rich diet helps reduce inflammation and supports a balanced gut microbiome⁸. You’ll find fibre in plant-based foods like fruit, vegetables, legumes, nuts, seeds and whole grains. You can also boost your intake with a fibre supplement.

Add prebiotics to your diet

Prebiotics are types of dietary fibre that feed the beneficial bacteria in your gut. These types of fibre pass through your digestive system without being broken down, eventually reaching the colon where they help beneficial bacteria – especially bifidobacteria and lactobacilli¹. You can get prebiotics naturally from foods like garlic, onions, bananas, leeks and asparagus, or you can supplement if needed.

Choose the right probiotics

Probiotics are beneficial bacteria that support your gut microbiome and may help gut-brain communication by reducing inflammation and supporting immunity¹. Different strains have different benefits, so ask your GP or pharmacist which one is right for you.

Additionally, fermented foods like sauerkraut, kimchi, kefir and tempeh are rich in natural probiotics and can help support a healthy gut microbiome⁹.

When to seek support for your gut health

If something doesn’t feel right, such as ongoing digestive symptoms or other gut-related concerns, it’s important to speak with your GP. They can assess your symptoms and decide whether further investigations are needed.

Depending on your symptoms, personal health history or family risk factors, your GP may also recommend screening tests, such as an endoscopy (to look for signs of stomach cancer) or a colonoscopy (to check for colorectal cancer).

Importantly, all Australians aged 45 to 74 are eligible for a free bowel screening test every two years through the National Bowel Cancer Screening Program. It’s a simple at-home test that could detect issues early on.

You can also consider consulting a dietitian. These qualified health professionals can provide practical strategies and tailored dietary advice to support the health, diversity and function of your gut microbiome.

Take a gut-friendly step forward

Making simple changes to your diet, such as adding more fibre, prebiotics, probiotics and fermented foods, can go a long way in supporting your gut-brain axis. If you’re not sure where to start, talk to your GP, dietitian or pharmacist for personalised advice.

You can also rest easy knowing that Zurich is here to support you with services such as the free My Wellbeing Hub, along with Zurich Evolve and a range of life insurance plans. Wherever you may be in your journey, we’re committed to helping you stay healthy and feel healthier.

References

1. Sayyed RZ, Khan M. Microbiome-gut-brain axis: implications on health. Singapore: Springer; 2022

2. Hyland N, Santon C. The gut-brain axis: dietary, probiotic, and prebiotic interventions on the microbiota. 2nd ed. Cork, Ireland: Academic Press; 2023

3. Australasian Gastro-intestinal Trials Group, ‘What is GI cancer?’, 2025

4. Alpert O, Begun L, Issac T, Solhkhah R. The brain-gut axis in gastrointestinal cancers. J Gastrointest Oncol. 2021 Jul;12(Suppl 2):S301-S310. doi: 10.21037/jgo-2019-gi-04

5. Mishra Y, Ranjan A, Mishra V, Chattaraj A, Aljabali AAA, El-Tanani M, Hromić-Jahjefendić A, Uversky VN, Tambuwala MM. The role of the gut microbiome in gastrointestinal cancers. Cell Signal. 2024 Mar;115:111013. doi: 10.1016/j.cellsig.2023.111013

6. Petracco G, Faimann I, Reichmann F. Inflammatory bowel disease and neuropsychiatric disorders: Mechanisms and emerging therapeutics targeting the microbiota-gut-brain axis. Pharmacol Ther. 2025 Feb;269. doi: 10.1016/j.pharmthera.2025.108831

7. Di YZ, Han BS, Di JM, Liu WY, Tang Q. Role of the brain-gut axis in gastrointestinal cancer. World J Clin Cases. 2019 Jul 6;7(13):1554-1570. doi: 10.12998/wjcc.v7.i13.1554

8. Feng Zhang, Dejun Fan, Jian-lin Huang, Tao Zuo, The gut microbiome: linking dietary fiber to inflammatory diseases, Medicine in Microecology, Volume 14, 2022. https://doi.org/10.1016/j.medmic.2022.100070

9. Balasubramanian R, Schneider E, Gunnigle E, Cotter PD, Cryan JF. Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health. Neurosci Biobehav Rev. 2024 Mar;158:105562. doi: 10.1016/j.neubiorev.2024.105562