IBS is a multi-factorial complex disease which is often confusing to patients and doctors alike.  But what does the recent literature say about the condition? We can glean some deeper understanding from the evidence and apply it to support our treatment of this common, chronic condition.


What is IBS and how does it affect our lives?

IBS is often diagnosed as a process of elimination once other conditions such as inflammatory bowel diseases have been ruled out. Diagnostic processes often involve blood and stool tests, symptom diaries and on occasion endoscopy type procedures to physically look at the state of the gastrointestinal tract1.  

The disease involves a combination of both abdominal pain, and altered bowel habits, occurring frequently for 6 months +2.  IBS involves altered transit times and effects on gut motility resulting in either constipation, diarrhoea or both. Additional symptoms including bloating, abdominal distention and cramping.   Beyond these symptoms, evidence suggests patients suffer from a reduction in quality of life3, largely due to symptoms effecting patients professional, social and private life.  There is a strong additional connection between IBS type issues and mental health conditions4; but this is not however suggesting the symptoms are ‘just caused by stress’, they are genuine and life altering. Instead this refers to the fascinating and well-established gut-brain axis and the effect that modulating one aspect of this axis has on the other5. It paves the way for potential therapeutic actions including mindfulness type approaches as part of the treatment picture.


Traditional treatment options

Traditionally treatment is limited to drugs targeting altered motility and pain, perhaps the use of antidepressants to act on the gut-brain axis1, and potential referral to a dietician to undertake a low-fodmap elimination and re-introduction diet6. Luckily the low-fodmap diet is helpful in up to 3 out of 4 sufferers and can help to identify avoidable triggers7. However the FODMAP diet does not address the ‘root cause’ of many cases  of IBS, is ineffective in 1 out of 4 cases, and cannot be adhered to long term due to both risk of nutritional deficiencies and adverse effects on the microbiome8.


What other factors may be involved in IBS?

Whilst there are different triggers for everybody and there is likely to be overlapping causes in many cases, there are some key themes within the literature. There is a wealth of literature regarding the gut microbiome variations specific to IBS sufferers9–11. These imbalances or alterations likely stem from gut-based infections, antibiotic overuse, unhelpful dietary patterns or additional lifestyle factors12.  There are general connections between ‘dysbiosis’ and IBS, however, now, there is additional emerging evidence regarding the specific microbes which may be elevated/depleted in sufferers13,14.  The reason this knowledge is useful is that we can modulate the microbiome through nutrition/ lifestyle interactions, giving us a method of treatment going beyond medication/ symptom suppression. 

What is SIBO and what does it have to do with IBS?

SIBO (small intestinal bacterial overgrowth) may be a factor for up to 78% of IBS cases15, despite being largely overlooked by the majority of traditional family doctors. Luckily, growing awareness is leading to testing and appropriate treatment in several cases.  SIBO occurs when certain microbes normally present within the large intestine, migrate to the small intestine and proliferate.  SIBO is a common consequence to reduced gastric acid production (IE by using commonly prescribed proton-pump inhibitors16). This causes excess fermentation and the consequential release of methane/ hydrogen in quantities enough to produce symptoms of distention/ bloating/ discomfort. Additionally, there may be effects on gut motility, as with IBS17. If your doctor is not confident with this condition, you can get privately tested, it is a simple breath test checking for levels of elevated hydrogen/ methane.  Elevated methane is mainly associated with IBS-C18 whereas increased hydrogen levels is connected to IBS-D. There are specific targeted antibiotic treatments for this condition, which has led to the elimination of IBS symptoms in patients19. However, it commonly relapses 20and requires dietary manipulation. Interestingly, exciting new research indicates a role for prebiotic use during treatment to prevent symptom relapse21.


Can we ‘see’ IBS?

IBS is a functional disease, this means, unlike inflammatory bowel diseases it is not strictly visible during endoscopy procedures, there is no obvious pathology, redness, inflammation etc. However recent evidence suggests that on a much more subtle level there are elevated chronic inflammatory cells during closer inspection of the intestinal mucosa22– especially in IBS-D. This is combined with subtle changes to the enteroendocrine and mast cells, indicating a potential role of inflammation, as is the case with so many chronic diseases.


Is intestinal permeability an issue?

When healthy, we benefit from a tightly knit protective intestinal lining, acting as a gateway to either permit or prevent pathogens and other molecules from entering or leaving our intestinal environment. When gaps form in this lining, and permeability is increased, we risk a range of inflammatory/ immune related responses.  There is also evidence indicating increased permeability may also play a role in increasing enhanced visceral sensitivity in IBS patients23– a key hallmark of this condition.  Permeability often occurs due to antibiotic overuse, stress and forms of dysbiosis24, and can be improved with the prebiotic inducing Short Chain Fatty Acid production which strengthens integrity25. Of course, with IBS, prebiotic tolerance is often limited (most FODMAP are a type of prebiotic) so this approach needs to be carefully implemented.



What about immune activation?

It is suggested than immune activation may play a role, both via the post-infectious IBS pathology processes and the elevated t-cell activation combined with mucosal inflammation26. Pro-inflammatory cytokines may be present within incidences of both IBS and their co-morbid altered mental states (anxiety/ depression) but this connection warrants further evaluation.  In practical terms, we can establish any food allergies which may be creating an immune response in connection with IBS27.



  • Whilst FODMAP elimination is a useful tool, recent evidence suggests other factors may be important in the treatment of IBS
  • Establishing the health of the microbiome can indicate levels of depleted/elevated microbes which are implicated in IBS pathology
  • Testing for SIBO may be important for individuals not responsive to low-FODMAP dietary approaches
  • Health of the gut lining may play a role in IBS- increasing integrity may be beneficial.
  • Understanding the potential role of immunity/ inflammation in IBS may help form future treatment options

If you have IBS and are looking for support managing this challenging condition please do contact me for further evidence based, personalised support.