Inflammatory Bowel Disease (IBD), including Crohn’s disease and Ulcerative Colitis, is a chronic inflammatory condition affecting the gastrointestinal tract. Symptoms such as abdominal pain, diarrhoea, urgency, fatigue, weight loss, and nutritional deficiencies can significantly affect daily life and overall wellbeing.

Research over the past decade has increasingly highlighted the role of the gut microbiome in both the development and progression of IBD. While the exact cause remains unclear, interactions between genetics, immune dysfunction, environmental triggers, and gut bacteria appear to play an important role.

 

Understanding the Gut Microbiome

The gut microbiome consists of trillions of microorganisms living within the digestive tract. These microbes contribute to:

  • Immune system regulation
  • Nutrient metabolism
  • Protection against pathogens
  • Intestinal barrier integrity
  • Production of short-chain fatty acids (SCFAs)

In healthy individuals, the microbiome exists in balance. In IBD, this balance may become disrupted—a phenomenon known as dysbiosis.

 

Crohn’s disease

1. Exclusive enteral nutrition
Still the most established dietary induction therapy, especially in paediatrics. It can reduce inflammation and induce remission, but adherence is the main barrier.

2. Crohn’s Disease Exclusion Diet + partial enteral nutrition
This is probably the most important emerging (but becoming) established whole-food approach. It excludes dietary components thought to drive dysbiosis/inflammation, including emulsifiers/additives, processed foods, animal fat, red/processed meat, gluten and dairy, while using partial formula support. Reviews describe CDED as a valid alternative to EEN in many mild–moderate paediatric and adult Crohn’s cases.

3. CD-TREAT / EEN-mimicking whole-food approaches
These aim to mimic the macronutrient and fibre profile of EEN using food rather than formula. Promising, but less widely embedded clinically than CDED.

4. Mediterranean diet
Useful as a long-term, sustainable baseline pattern. In the DINE-CD trial, Mediterranean diet performed similarly to the Specific Carbohydrate Diet for symptom improvement in mild–moderate Crohn’s, with better practicality.

 

Ulcerative colitis

1. Mediterranean-style diet
Likely the most practical remission-support diet: high in extra virgin olive oil, fish, legumes if tolerated, vegetables, fruit, nuts/seeds, herbs/spices and whole grains where tolerated; low in ultra-processed foods and processed meats. ECCO-linked summaries note Mediterranean diet and limiting red meat may be considered for maintaining remission in UC.

2. Low-sulphur / low-sulphide-producing approaches
This is emerging particularly for UC, given interest in hydrogen sulphide, mucosal barrier effects and sulphur-metabolising bacteria. Practically, this may mean moderating high intakes of red meat, processed meat, eggs, sulphur preservatives and some additives, rather than creating a highly restrictive diet.

3. Plant-forward, fibre-diverse but personalised
The direction of travel is not low fibre forever, but strategic fibre reintroduction once inflammation is controlled. The goal is butyrate production, mucosal support and microbial diversity, while adjusting texture/residue during flares.

4. Low-additive / minimally processed diet
Increasing interest across both UC and Crohn’s. The focus is reducing emulsifiers, maltodextrin, carrageenan, artificial sweeteners, processed meats and ultra-processed foods. This is biologically plausible and clinically sensible, though not yet as trial-proven as CDED for Crohn’s.

 

What Does the Research Show?

 

Reduced Microbial Diversity

Studies consistently demonstrate that individuals with IBD tend to have lower microbial diversity compared to healthy controls. Reduced diversity is associated with increased intestinal inflammation and poorer gut resilience.

 

Changes in Beneficial Bacteria

Research has shown lower levels of beneficial bacterial species such as:

  • Faecalibacterium prausnitzii
  • Roseburia
  • Bifidobacterium species

These bacteria are involved in producing butyrate, an anti-inflammatory short-chain fatty acid essential for intestinal health.

 

Increase in Pro-inflammatory Microbes

Some studies have identified increased levels of potentially pro-inflammatory bacterial strains during active disease states, although it remains unclear whether these changes are a cause or consequence of inflammation.

 

Diet and IBD

Nutrition plays an important supportive role in IBD management. While no single diet cures IBD, dietary strategies may assist with:

  • Nutritional adequacy
  • Symptom management
  • Supporting microbial diversity
  • Reducing inflammation
  • Improving quality of life

 

Emerging Dietary Approaches

Emerging dietary approaches for UC and Crohn’s are moving away from avoid trigger foods and toward diet as a disease-modifying therapy, especially in Crohn’s. The strongest evidence is still for exclusive enteral nutrition and CDED in Crohn’s, while UC evidence is more around Mediterranean-style, low-sulphur/low-additive, plant-forward patterns for remission support rather than induction. ECCO’s 2025 consensus now formally recognises diet as part of IBD management, not just nutritional support.

 

Low FODMAP Diet

Some individuals with IBD also experience functional gut symptoms such as bloating and abdominal discomfort. In selected cases, a short-term low FODMAP approach may help symptom management under professional guidance.

 

Exclusive Enteral Nutrition (EEN)

Particularly in paediatric Crohn’s disease, EEN has demonstrated effectiveness in inducing remission and improving nutritional status.

 

Mental Health and IBD

The relationship between the gut and brain is increasingly recognised in chronic gastrointestinal conditions. Stress, anxiety, and depression may influence symptom severity and overall disease burden.

Supporting mental wellbeing forms an important part of holistic IBD management.

 

Final Thoughts

IBD is a complex condition involving inflammation, immune regulation, and the gut microbiome. While medical treatment remains essential, personalised nutrition and lifestyle strategies may offer additional support for symptom management and long-term gut health.

Working with a multidisciplinary healthcare team, including a gastroenterologist and dietitian, can help individuals navigate IBD more effectively while maintaining nutritional adequacy and quality of life.