Nausea, constipation, diarrhoea, and a feeling of ‘butterflies’ in the stomach are symptoms we have probably all experienced when stressed.

This is the ‘gut-brain axis’ in action, a term that recognises the impact of emotions on gut health and vice versa. We have known about this for a long time, from early recognition that irritable bowel syndrome (IBS) is common in those with psychiatric diagnoses.

However, there are many proposed environmental, physical, genetic, and nutritional links to IBS, not just the psychological ones. This article will explore the foundations of our gut and examine the latest research on IBS, the gut microbiome, the gut-brain axis, and the role our immune system plays in gastrointestinal disease.

What is IBS?

Irritable Bowel Syndrome is a common condition that affects the digestive system, characterised by symptoms that may include abdominal pain, bloating, gas, and altered bowel habits (loose stool, constipation, or both).

The exact cause of IBS is not fully understood, but it is believed to involve a combination of factors, including how your gut muscles move (gut motility), how sensitive your gut is to pain or discomfort (gut sensitivity), and the connection between your digestive system and your brain (gut-brain axis).

What is the Gut Microbiome?

The gut microbiome consists of trillions of microorganisms, including bacteria, viruses and fungi, to name a few, that inhabit the digestive tract. These microbes are crucial for various functions, including digestion, immunity, and mental health.

What is the connection between Gut Microbiome and IBS?

1. Dysbiosis: Many studies have found that individuals with IBS often exhibit dysbiosis, an imbalance in the gut microbiome. This can involve a decrease in beneficial bacteria and an increase in harmful bacteria.
2. Inflammation: Some gut bacteria can promote inflammation, which may contribute to IBS symptoms. Inflammation in the gut can lead to changes in gut permeability, often referred to as “leaky gut.” While leaky gut syndrome is a theory that has yet to be recognised as a medical diagnosis, it suggests that some people’s guts allow more harmful substances into the bloodstream, potentially triggering an inflammatory response.
3. Metabolites: Gut bacteria produce various substances, including short-chain fatty acids (SCFAs). SCFAs are produced when bacteria ferment fibre in the colon and play a key role in gut health by supporting the gut lining, reducing inflammation, and influencing the immune system. Altered levels of SCFAs in IBS patients can impact gut function and symptom severity.
4. Diet and Microbiome: Diet significantly influences the gut microbiome. Certain diets, like those high in fibre or specific fermentable carbohydrates (FODMAPs), can help alleviate IBS symptoms by promoting beneficial bacteria. FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides and Polyols) are types of carbohydrates that some people find hard to digest, and reducing their intake can help improve symptoms in some IBS patients.
5. Probiotics and Treatments: Some probiotics (beneficial bacteria that help balance your gut) have shown promise in improving IBS symptoms by restoring a healthy balance in the gut microbiome. However, results can vary, and specific strains may be more effective than others.

What is leaky gut syndrome?

Leaky gut syndrome is a theory based on the concept of increased intestinal permeability. Normally, the lining of the gut acts as a barrier, allowing water and nutrients to pass into the bloodstream while keeping harmful substances out.

In some individuals, this barrier becomes more permeable, allowing larger, potentially harmful molecules like toxins or bacteria to enter the bloodstream. While increased intestinal permeability is a real condition, the idea that it directly causes other illnesses remains unproven. As a result, leaky gut syndrome is not currently a recognised medical diagnosis.

However, identifying specific dietary triggers or irritants can sometimes help improve gut function and reduce symptoms for individuals experiencing related issues.

How does the Microbiome affect our Mood?

For many years, mental health was seen as only a problem of the mind and not linked to the processes and functioning of the body that houses the mind. It has long been known that people with mental health conditions often experience physical symptoms as well, such as gut issues frequently labelled as IBS, but the connection between the two wasn’t well understood.

Thankfully, change is upon us. An approach to mental healthcare that recognises the link between our mind, body, and environment is gaining momentum. Research into factors like nutrition, lifestyle, and our surroundings is giving us more ways to support mental health.

One key part of this new understanding is that the microbes living in our gut can influence our mood, either positively or negatively. Taking care of the gut microbiome can become an additional tool for improving mental health alongside exercise, social interaction, therapy, medication, and lifestyle changes.

We now know that gut bacteria help regulate the “gut-brain axis”—the connection between our gut and brain. A major study showed that when gut bacteria from people with depression were transplanted into germ-free rats (rats raised without any bacteria), the rats developed depression-like symptoms. More recent research has found clear differences in the gut microbiomes of people with mental health conditions.

Humans have always lived with microbes, and there has never been a time when the brain didn’t receive signals from the microbes in our gut. These microbes can influence our behaviour, immune system and mood. And in return, we can influence them—through our diet, stress levels, and other lifestyle factors. Disruptions in the communication between our gut and brain have been linked to various health problems, including anxiety, psychiatric disorders, addiction, obesity, and IBS.

What lifestyle changes are recommended?

• Dietary Changes: Implementing a high-fibre intake or trialling a low-FODMAP diet can help regulate symptoms. This often involves a longer discussion with one of our GPs or a dietician to explore the best diet for each patient.
• Probiotics: The evidence is increasing towards the benefit of pre and probiotics. Many are found in natural food sources but there are also some evidence-based brands that have shown to benefit some patients. Our GPs can help determine whether probiotics may be helpful for you.
• Stress Management: Since the gut-brain axis plays a role in IBS, managing stress through mindfulness, therapy or exercise can be beneficial. Our GPs can recommend the most suitable therapies and techniques for improving stress and mental health.

We’ve all noticed how we become withdrawn, tired, and lose interest in things when we’re fighting an infection. This “sickness behaviour,” which mimics depression, is an acute response intended to help the body heal during inflammation caused by infection.

However, when inflammation signals come from multiple sources — such as an imbalance in gut bacteria (dysbiosis) or a weak gut barrier — and these signals cross the blood-brain barrier (the protective layer around the brain that keeps harmful substances out) without being resolved, they can lead to long-term changes in mood and behaviour, similar to depression. Inflammation from dysbiosis in the mouth, such as gum disease, has also been linked to a higher risk of depression and fatigue.

Conclusion

While the gut microbiome is not the sole cause of IBS, it plays a critical role in its manifestation and management. Understanding this relationship can help in developing personalised treatment plans for those affected by IBS.

If you have symptoms that may be related to IBS, gut and/or mood imbalances, working with one of our GPs can lead to more effective management strategies.

To book an appointment online click here or call us on 0207 245 3999.

References

https://pmc.ncbi.nlm.nih.gov/articles/PMC8819474/
https://pmc.ncbi.nlm.nih.gov/articles/PMC7127849/
https://www.ifm.org/