Gut Microbiome and Crohn’s Disease

The human body hosts trillions of microorganisms, collectively known as the gut microbiome, a dynamic ecosystem that acts like a second brain, influencing the immune system, metabolism, mood, and even the development of inflammatory diseases.

Crohn’s disease, a chronic inflammatory bowel disease (IBD), is a classic example in which the balance of the gut microbiome is disrupted. Although the causes of the disease remain partially unknown, in recent years, science has turned to the microbiome to seek answers, prevention strategies, and personalized therapeutic approaches.

For patients diagnosed with Crohn’s disease or individuals who belong to a high-risk group (family history, chronic gastrointestinal symptoms, weak immune system), understanding the role of the microbiome in the context of this disease is critical.

The microbiome is a useful tool for diagnosis, prevention, and in some cases the target of treatment or the means to symptom relief. Through specialized functional tests, we can accurately map the condition of your gut and chart a path for personalized intervention that is based on the pathophysiology and the underlying causes of Crohn’s disease

The Biology and Pathophysiology of Crohn’s Disease: A Window into the Intestinal Ecosystem

Crohn’s disease is a chronic inflammatory condition that can affect any part of the gastrointestinal tract, from the mouth to the anus, with the most common sites being the terminal ileum and the colon. It is a disease characterized by patchy areas of inflammation, in contrast to ulcerative colitis, where inflammation is continuous.

Although Crohn’s disease is multifactorial, the last decade has clearly highlighted the significance of dysbiosis, i.e., disruption of the gut microbiome’s balance. A healthy person’s microbiome includes a wide array of beneficial bacteria that produce short-chain fatty acids (SCFAs), regulate immune responses, and maintain the integrity of the intestinal barrier. In Crohn’s disease, this balance collapses.

What happens biologically?

• Increased intestinal permeability: Patients with Crohn’s show reduced expression of proteins that tightly bind intestinal cells together, leading to leakage of antigens, bacteria, and toxins into the bloodstream.
• Uncontrolled immune activation: Immune cells mistake friendly bacteria for threats, triggering chronic inflammation.
• Disrupted host-bacteria interaction: Beneficial bacteria (e.g., Faecalibacterium prausnitzii) are reduced, while potentially pathogenic species (e.g., Escherichia coli), associated with inflammation, increase.
• Production of pro-inflammatory cytokines: Elevated levels of IL-6, TNF-α, and other molecules promote and sustain inflammation.
   

According to a recent study, Crohn’s disease is characterized by an increased presence of bacteria that promote the production of sulfur compounds and a decrease in species that protect the intestinal lining, such as butyrate producers. This imbalance is not just a result of the disease, but also an active contributor to its progression.

Moreover, specific microbial metabolites, such as secondary bile acids, have been shown to directly influence patients' response to biologic therapies such as infliximab. These findings underscore the need for personalized therapeutic approaches tailored to the individual’s microbiome profile.

Functional Medicine in Crohn’s Disease: From Inflammation to Personalization

Functional Medicine views chronic inflammatory conditions such as Crohn’s disease as dynamic manifestations of systemic dysfunction, focusing on the underlying causes rather than just the symptoms. At the heart of this approach lies the microbiome. Understanding the interactions among bacteria, the intestinal barrier, the immune system, and the neuroendocrine system enables the development of personalized therapeutic strategies. While conventional medicine primarily focuses on controlling inflammation with immunosuppressants or biological agents, the functional approach:

• Seeks out predisposing factors (genetic, environmental, metabolic)
• Identifies nutritional deficiencies or overloads that worsen inflammation
• Recognizes systemic interactions (e.g., microbiome-brain, gut-liver-skin axis)
• Applies advanced diagnostic methods that detect subtle dysfunctions not visible through standard testing
• Aims to restore intestinal ecology
   

Biomarkers and Tests That Illuminate the Underlying Causes
The functional approach offers a broad spectrum of tests capable of detecting underlying dysfunctions, even when conventional examinations appear normal. Indicatively:

• EnteroScan®: An extensive microbiome analysis, serving as a starting point for every personalized intervention,which evaluates bacterial diversity and balance, the presence of potentially pathogenic species or biofilm-related bacteria, the production of butyric acid and other SCFAs, as well as markers of inflammation, malabsorption, and immune stimulation.
• ImmuneScan®: Analysis of a number of biomarkers that detect active or low-grade inflammation (e.g., hs-CRP, IL-6, TNF-α). For example, IL-6 is often elevated during flare-ups, while CRP correlates with the disease’s activity level.
• NutriScan®: Comphrehensive assessment of fat-soluble and water-soluble vitamins, such as B-complex vitamins, essential for methylation, hematopoiesis, and cell regeneration, Vitamin D, crucial for immune regulation, or Vitamin K, linked to epithelial health and inflammation balance.
• Metals & Traces®: Evaluation of trace elements, such as Zinc, which promotes intestinal barrier healing and inflammation control, or Magnesium, which is critical for bowel motility, cortisol regulation, and energy production.
• DetoxScan®: Assessment of oxidative stress levels that reveals the body’s balance against oxidative load, measuring markers like plasma’s Total Antioxidant Capacity (TAC), or the evaluation of the body’s detoxification mechanisms.
• Metabolomix™: Detailed profile of functional metabolites, such as organic acids of intestinal and systemic metabolism, microbial metabolites (indoles, phenols, skatoles) linked to inflammation and intestinal permeability, as well as indicators of mitochondrial function, neurotransmitters, and gut absorption.
   

Personalization and Redefinition of Therapy
Crohn’s disease is not the same for every individual. Some patients exhibit primary inflammation, others secondary dysbiosis, and others still show reduced detoxification capacity or epigenetic changes that trigger immune responses. Based on the above data:

• A diet can be designed specifically tailored to the patient’s microbial composition and nutritional needs
• Supplements are chosen based on actual laboratory findings, not assumptions
• It becomes clear when intervention with biological agents is appropriate, and when restoration of the microbiome through diet or even fecal microbiota transplantation (FMT) is necessary

Diet and Lifestyle in Crohn’s Disease: The Foundation for Inflammation Control

The everyday life of a Crohn’s patient is often unstable, affected by flare-ups, restrictions, and the uncertainty of the diagnosis. However, clinical data and scientific studies are clear: diet and lifestyle can reshape the microbiome, reduce inflammation, and improve prognosis.

According to recent reviews, consumption of ultra-processed foods is associated with worsening intestinal inflammation, disrupted bacterial diversity, and increased pathogens. At the same time, traditional anti-inflammatory diets (like the Mediterranean diet) promote the restoration of protective bacteria such as Faecalibacterium prausnitzii.

Nutritional and lifestyle tips, as well as complementary strategies, are presented in more detail below.

Core Nutritional Guidelines for Crohn’s Disease

• Increase dietary fiber (where permitted). During remission phases, the gradual introduction of prebiotic fibers (e.g. from chicory root, resistant starch) can nourish beneficial bacteria. Caution: During active inflammation or strictures, fiber may cause discomfort.
• Avoid immune-reactive dietary triggers affecting the intestinal mucosa, such as ultra-processed foods, additives, artificial sweeteners, Gluten and casein or high-sulfur foods (e.g., preservatives, processed meats)
• Support short-chain fatty acid (SCFA) production. Butyric acid is produced by gut bacteria and has proven anti-inflammatory effects on the intestinal epithelium. Foods like boiled lentils, beans, bananas, and cold boiled potatoes support such bacteria and can help produce butyric acid.
• Ensure adequate intake of omega-3s and antioxidants, via fatty fish (sardines, mackerel, salmon), cold-pressed olive oil, berries, or leafy green vegetables
   

Additional Lifestyle Interventions

• Stress and the microbiome: Elevated cortisol alters microbiome composition and increases gut permeability. Techniques like diaphragmatic breathing, yoga, or guided relaxation (e.g. mindfulness apps) are essential, especially during flare-ups.
• Sleep and circadian rhythm. Poor sleep is linked to microbiome alterations and heightened inflammation. A consistent sleep schedule, avoidance of screens before bed, and morning sunlight exposure are recommended.
• Exercise tailored to disease phase. Mild physical activity (e.g. walking, swimming) helps rebuild the microbiome and restore bowel motility. Avoid overtraining during flare-ups.
   

Complementary Strategies

• Targeted probiotics (informed by microbiome analysis): Not all probiotics are suitable. Selection is based on gut microbiome analysis results and specific species present
• Prebiotics (inulin, FOS, GOS): Can be tailored according to gut tolerance and microbiome profile
• Glutamine and zinc: Support healing of the intestinal barrier
• Antioxidants, such as curcumin or resveratrol: Modulate inflammation and immune function

Conclusions and Next Steps

Crohn’s disease is a systemic inflammatory condition rooted in the interaction between hormonal dysregulation, microbial imbalance, and environmental triggers. The gut microbiome acts as a central regulator of inflammation, immune response, and overall homeostasis of the body. Therefore, its dysregulation can influence the progression and outcome of inflammatory conditions such as Crohn’s disease.

Functional medicine aims to understand the root cause of disease and develop personalized interventions. The microbiome is not static; it changes, adapts, and is influenced by what we eat, how we sleep, and the stress we experience. The ability to analyze, understand, and rebalance this ecosystem is now more achievable than ever.

References

1. Agrawal H, Gupta N. Comparative analysis of the pathogenesis in Crohn's disease and ulcerative colitis. World J Gastroenterol. 2025;31(29):109892. doi:10.3748/wjg.v31.i29.109892
2. Liu L, Liang L, Liang H, et al. Microbiome-metabolome generated bile acids gatekeep infliximab efficacy in Crohn's disease by licensing M1 suppression and Treg dominance. J Adv Res. Published online August 12, 2025. doi:10.1016/j.jare.2025.08.017
3. Kanta D, Katsamakas E, Gudiksen AMB, Jalili M. Histamine Metabolism in IBD: Towards Precision Nutrition. Nutrients. 2025;17(15):2473. Published 2025 Jul 29. doi:10.3390/nu17152473
4. Spiller AL, Costa BGD, Yoshihara RNY, et al. Ultra-Processed Foods, Gut Microbiota, and Inflammatory Bowel Disease: A Critical Review of Emerging Evidence. Nutrients. 2025;17(16):2677. Published 2025 Aug 19. doi:10.3390/nu17162677