Irritable bowel syndrome (IBS) affects an estimated 10-15 per cent of the global population, making it one of the most common functional gastrointestinal disorders. Despite its prevalence, many people with IBS feel frustrated by the conventional approach, which often focuses on managing symptoms with medication rather than identifying and addressing the underlying causes. Functional medicine offers a different perspective — one that seeks to understand why the gut is malfunctioning and what can be done to restore normal function.
Understanding IBS
IBS is characterised by recurrent abdominal pain associated with changes in bowel habits. It is typically classified into subtypes based on the predominant stool pattern:
IBS-D (diarrhoea-predominant) — Frequent loose or watery stools, often with urgency
IBS-C (constipation-predominant) — Infrequent, hard or difficult-to-pass stools
IBS-M (mixed) — Alternating between diarrhoea and constipation
IBS-U (unsubtyped) — Symptoms that do not fit neatly into the other categories
Common symptoms across all subtypes include bloating, abdominal distension, excessive gas, mucus in stools, incomplete evacuation and symptoms that worsen with stress or after eating.
Root Causes of IBS: Beyond the Diagnosis
In functional medicine, IBS is not viewed as a final diagnosis but rather as a description of symptoms that can have multiple underlying causes. Identifying these root causes is the key to effective, lasting treatment.
Small Intestinal Bacterial Overgrowth (SIBO)
SIBO occurs when bacteria that normally reside in the large intestine migrate into the small intestine, where they ferment carbohydrates and produce excessive gas. Research suggests that SIBO may be present in up to 78 per cent of IBS cases. Symptoms include bloating within 30-60 minutes of eating, excessive belching and flatulence, abdominal pain and alternating bowel habits.
Gut Dysbiosis
An imbalanced gut microbiome — with reduced diversity and altered ratios of beneficial to pathogenic organisms — is consistently found in IBS patients. Factors such as antibiotic use, poor diet, stress and infections can all contribute to dysbiosis.
Post-Infectious IBS
Approximately 10-15 per cent of people who experience acute gastroenteritis (food poisoning or stomach bugs) go on to develop IBS. The infection triggers changes in the gut microbiome, immune system and nervous system that persist long after the original illness has resolved.
Food Sensitivities and Intolerances
Many people with IBS react to specific foods or food groups. Common triggers include FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), gluten, dairy, histamine-rich foods and certain food additives.
Gut-Brain Axis Dysfunction
The communication between the gut and the brain plays a central role in IBS. Visceral hypersensitivity — where the gut nerves become overly reactive to normal stimuli such as gas or stretching — is a hallmark of the condition. Stress, anxiety and trauma can amplify this sensitivity.
Bile Acid Malabsorption
In IBS-D, bile acid malabsorption is an underdiagnosed cause. When bile acids are not properly reabsorbed in the small intestine, they reach the colon and stimulate fluid secretion and motility, causing watery diarrhoea.
The Functional Medicine Approach to IBS
Rather than prescribing a blanket treatment, functional medicine uses a personalised, investigative approach:
Comprehensive Testing
Stool analysis — A comprehensive stool test evaluates the microbiome composition, inflammation markers (calprotectin), digestive enzyme levels, short-chain fatty acid production and the presence of parasites or pathogenic bacteria.
SIBO breath test — Measures hydrogen and methane gas production after ingesting a sugar solution, helping to identify bacterial overgrowth in the small intestine.
Food sensitivity testing — While not a replacement for an elimination diet, IgG food sensitivity panels can help identify potential trigger foods.
Blood work — Thyroid function, coeliac markers, inflammatory markers and nutrient levels (iron, B12, vitamin D) provide important context.
Targeted Dietary Interventions
The low-FODMAP diet — A well-researched approach that reduces fermentable carbohydrates for 4-6 weeks, followed by systematic reintroduction to identify individual triggers. Studies show it improves symptoms in approximately 75 per cent of IBS patients.
Elimination diets — Removing common trigger foods (gluten, dairy, soy, eggs, corn) for 3-4 weeks and reintroducing them one at a time can reveal hidden sensitivities.
Specific Carbohydrate Diet (SCD) — May be beneficial for those who do not respond to the low-FODMAP approach.
Microbiome Restoration
Targeted probiotics — Specific strains have demonstrated benefits for IBS, including Bifidobacterium infantis 35624, Lactobacillus plantarum 299v and the multi-strain VSL#3 formulation.
Prebiotic foods — Introduced gradually to nourish beneficial bacteria without exacerbating symptoms.
Antimicrobial protocols — For SIBO or pathogenic overgrowth, herbal antimicrobials (such as oregano oil, berberine and allicin) or targeted antibiotics may be used.
Nervous System Support
Vagus nerve stimulation — Techniques such as deep breathing exercises, cold water exposure, gargling and humming can activate the vagus nerve and improve gut-brain communication.
Stress management — Cognitive behavioural therapy (CBT), gut-directed hypnotherapy and mindfulness meditation have all shown significant benefits for IBS in clinical trials.
Regular movement — Moderate exercise such as walking, yoga and swimming supports gut motility and reduces stress hormones.
Living Well with IBS
Eat mindfully — Chew thoroughly, eat slowly and avoid eating while stressed or distracted. This simple practice can significantly reduce bloating and improve digestion.
Keep a food and symptom diary — Tracking what you eat alongside your symptoms helps identify patterns and triggers that may not be immediately obvious.
Prioritise [sleep](/resources/articles/gut-health-sleep-connection/) — Poor sleep worsens IBS symptoms. Aim for 7-9 hours of quality sleep and maintain a consistent sleep schedule.
Stay hydrated — Adequate water intake supports healthy bowel movements and digestive function.
The Bottom Line
IBS does not have to be a life sentence of symptom management. By identifying the specific root causes driving your symptoms — whether that is SIBO, dysbiosis, food sensitivities, nervous system dysfunction or a combination — a functional medicine approach can help you achieve lasting relief and restore normal gut function. If you have been told there is nothing more that can be done for your IBS, it may be time to look deeper.