SIBO (Small Intestinal Bacterial Overgrowth) is one of the most underdiagnosed causes of chronic digestive issues. Persistent post-meal bloating, abdominal pain, unexplained diarrhoea or constipation, chronic fatigue: these symptoms you may know all too well could have a precise explanation and, most importantly, concrete solutions.
Scientific research has considerably advanced our understanding of SIBO in recent years. We now know that it is not a simple "infection" but rather a complex imbalance of the intestinal ecosystem, involving specific mechanisms that can be identified and treated in a targeted way. The diagnostic threshold has been lowered from 105 to 103 CFU/mL, reflecting a more refined understanding of this condition.
Our promise at Diaeta: personalized nutritional support, based on the latest scientific evidence, that allows you to regain your digestive comfort without ever feeling hungry and while continuing to eat foods you find delicious. Every gut is unique, and your care should be too.
1. Understanding SIBO: Much More Than Excess Bacteria
The small intestine, unlike the colon, is normally a low-bacterial-density environment. It is in this organ, measuring 6 to 7 metres in length, that most digestion and nutrient absorption takes place. When bacteria settle there in excessive numbers, they directly interfere with these vital functions.
SIBO is not a simple passive migration of bacteria from the colon to the small intestine. Modern research shows that it is an opportunistic expansion of specific microbial taxa, primarily organisms within the phylum Proteobacteria. Two species emerge as the main actors: Escherichia coli and Klebsiella pneumoniae.
1.1 What these bacteria do in the small intestine
These microorganisms act as true disruptors:
- Reduction of microbial diversity: they outcompete the beneficial species normally present
- Brush border damage: the intestinal villi, essential for absorption, are damaged
- Metabolic hijacking: they ferment nutrients before your body can absorb them, producing gases and irritating metabolites
- Premature bile acid deconjugation: disrupting fat digestion and potentially causing steatorrhoea
Key insight: Modern SIBO is no longer defined by a threshold of 105 CFU/mL as in the past. The current consensus (American College of Gastroenterology) has lowered this threshold to 103 CFU/mL, as healthy individuals virtually never exceed this concentration in the duodenum or proximal jejunum.
2. The Four Faces of Intestinal Overgrowth
One of the major advances in recent research is the recognition that SIBO is not a single entity. There are four distinct forms, each involving different microorganisms, producing different gases and requiring specific therapeutic approaches.
| Type | Microorganisms | Gas Produced | Clinical Profile |
|---|---|---|---|
| Hydrogen SIBO | E. coli, Klebsiella pneumoniae | Hydrogen (H2) | Diarrhoea-predominant, bloating |
| IMO (Intestinal Methanogen Overgrowth) | Methanobrevibacter smithii (archaea) | Methane (CH4) | Constipation-predominant, distension |
| ISO (Intestinal Sulfide Overproduction) | Desulfovibrio, Fusobacterium, Bilophila wadsworthia | Hydrogen sulfide (H2S) | Severe diarrhoea, brain fog, intense fatigue |
| SIFO (Small Intestinal Fungal Overgrowth) | Candida species | No detectable gas | Similar to SIBO symptoms, undetectable on breath test |
2.1 Hydrogen SIBO: the classic type
This is the best-known form. Bacteria ferment fermentable carbohydrates (FODMAPs) and produce hydrogen. This gas causes bloating, abdominal distension and diarrhoea. It is associated with diarrhoea-predominant irritable bowel syndrome (IBS-D).
2.2 IMO: when methane slows everything down
IMO (formerly methane SIBO) is caused not by bacteria but by methanogenic archaea, primarily Methanobrevibacter smithii. These organisms consume the hydrogen produced by other microorganisms to generate methane. Methane acts as a true intestinal paralytic, slowing transit and causing often severe constipation. This is why the term "IMO" (rather than "methane SIBO") is now preferred: these archaea can proliferate throughout the intestine, not just the small intestine.
2.3 ISO: hydrogen sulfide, a formidable disruptor
ISO is produced by sulfate-reducing bacteria. Hydrogen sulfide is particularly problematic because it can appear as a "flatline" on traditional breath tests that only measure hydrogen and methane. ISO patients often present with marked systemic symptoms: brain fog, intense fatigue and severe diarrhoea.
2.4 SIFO: fungal overgrowth
SIFO involves excessive growth of yeasts, primarily Candida species, in the small intestine. It cannot be detected by a breath test and requires direct aspiration with culture. It often coexists with bacterial SIBO.
Key insight: If your breath tests show a "flatline" (no rise in hydrogen or methane) but your symptoms persist, hydrogen sulfide overproduction (ISO) or fungal overgrowth (SIFO) could be the cause. A tri-gas test including H2S is then recommended.
3. How SIBO Develops: The Mechanisms at Play
Your body has several natural defence mechanisms to prevent bacterial overgrowth in the small intestine. When these defences are compromised, SIBO can develop.
3.1 The Migrating Motor Complex (MMC): your "intestinal broom"
The MMC is a pattern of motor activity that occurs during fasting periods, every 90 to 120 minutes. It generates powerful contractions that sweep food debris and bacteria towards the colon. It is your primary defence against bacterial overgrowth in the small intestine.
The MMC only functions when you are fasting. This is why constant snacking or meals too close together can disrupt this protective mechanism.
3.2 Post-infectious autoimmunity: when food poisoning triggers SIBO
This is one of the most important discoveries in recent years. Certain bacteria responsible for food poisoning (Campylobacter, Salmonella, pathogenic E. coli) produce a toxin called CdtB (Cytolethal Distending Toxin B). The immune system produces antibodies against this toxin, but through a phenomenon of molecular mimicry, these antibodies also attack vinculin, a structural protein essential for the interstitial cells of Cajal (ICC) — the "pacemaker" cells of the intestine that orchestrate the MMC.
Result: the MMC is chronically damaged, and SIBO develops on a recurring basis. Serological tests measuring anti-CdtB and anti-vinculin antibodies have a specificity of 93.5% for post-infectious IBS-D.
3.3 Other risk factors
- Proton pump inhibitors (PPIs): SIBO prevalence in PPI users is 36.8% compared to 19.8% in non-users. Each additional month of use increases SIBO risk by 4.265%
- Motility disorders: systemic sclerosis, diabetic neuropathy, hypothyroidism
- Anatomical abnormalities: small bowel diverticula, post-surgical adhesions, strictures
- Pancreatic insufficiency: reduced digestive enzymes
- Gastric acid deficiency: achlorhydria, atrophic gastritis
- Age: prevalence increases with age due to natural slowing of motility
Key insight: If you developed chronic digestive issues after an episode of food poisoning or gastroenteritis, the post-infectious autoimmune mechanism could be the cause. This information is valuable for guiding your care.
4. Recognizing SIBO Symptoms
SIBO symptoms are often confused with those of irritable bowel syndrome (IBS), which is not surprising since SIBO is considered a frequent underlying cause of IBS.
4.1 Digestive symptoms
- Postprandial bloating: often the most bothersome symptom, worsening throughout the day
- Abdominal distension: visible increase in abdominal volume
- Abdominal pain: cramps, diffuse or localized discomfort
- Excessive flatulence: increased gas production
- Diarrhoea: typical of hydrogen SIBO and ISO
- Constipation: characteristic of IMO (methane)
- Alternating diarrhoea-constipation: possible with mixed forms
- Nausea: particularly after meals rich in fibre or FODMAPs
4.2 Systemic symptoms
SIBO is not limited to the digestive sphere. Intestinal barrier disruption and bacterial metabolites can cause:
- Chronic fatigue: related to nutritional deficiencies and systemic inflammation
- Brain fog: difficulty concentrating, feeling of mental cloudiness (particularly marked in ISO)
- Joint pain: systemic inflammation linked to intestinal permeability
- Skin manifestations: rosacea, eczema, acne — the gut-skin connection
- Mood disturbances: anxiety, irritability linked to the gut-brain axis
5. Nutritional Impact: Deficiencies to Watch For
Bacterial overgrowth in the small intestine can lead to significant nutritional deficiencies that your dietitian should look for and correct.
| Nutrient | Mechanism of Deficiency | Consequences |
|---|---|---|
| Vitamin B12 | Consumed by excess bacteria | Fatigue, neurological disorders, anaemia |
| Iron (low ferritin) | Malabsorption, bacterial competition | Fatigue, pallor, breathlessness |
| Fat-soluble vitamins (A, D, E, K) | Bile acid deconjugation disrupting fat absorption | Osteoporosis (D), visual disorders (A), coagulopathy (K) |
| Folate | Paradoxically elevated — produced by excess bacteria | Elevated folate with low B12 is a suggestive indicator of SIBO |
Key insight: A blood profile showing low vitamin B12 with paradoxically elevated folate is a characteristic biological indicator of SIBO. This is something your dietitian and doctor will look for in your blood work.
6. Diagnosing SIBO: Tests and Interpretation
SIBO diagnosis relies primarily on two complementary approaches.
6.1 Small bowel aspiration: the gold standard
Jejunal aspiration with culture remains the reference. A sample is taken during upper endoscopy, and a bacterial culture is performed. The current diagnostic threshold is ≥ 103 CFU/mL. This method is invasive and costly, which is why it is not used as a first-line test.
6.2 Breath tests: the first-line tool
Breath tests measure gases produced by bacterial fermentation in the small intestine. Two substrates are used:
| Test | Substrate | Specificity | Sensitivity | Area Explored |
|---|---|---|---|---|
| Glucose test | 75 g glucose | 83.2% | 54.5% | Proximal small intestine |
| Lactulose test | 10 g lactulose | 70.6% | Higher | Entire small intestine |
6.3 Tri-gas breath test: the diagnostic advance
Latest-generation devices measure three gases simultaneously: hydrogen (H2), methane (CH4) and hydrogen sulfide (H2S). The diagnostic criteria are:
- Hydrogen SIBO: H2 rise ≥ 20 ppm within the first 90 minutes
- IMO: methane ≥ 10 ppm at any point during the test
- ISO: H2S elevation (thresholds are still being standardized)
6.4 Serology: post-infectious antibodies
Tests measuring anti-CdtB and anti-vinculin antibodies can confirm a post-infectious origin. With a specificity of 93.5% for post-infectious IBS-D, they represent a valuable complementary diagnostic tool.
Key insight: A negative breath test does not necessarily rule out intestinal overgrowth. ISO (hydrogen sulfide) and SIFO (fungal) can go undetected with standard tests measuring only H2 and CH4.
7. Therapeutic Strategies: A Comprehensive Approach
SIBO treatment is multimodal, combining targeted antimicrobial treatment and nutritional management. It is important to note that medication is prescribed by your doctor; the dietitian's role is to optimize the nutritional approach to maximize treatment effectiveness and prevent relapse.
7.1 Antimicrobial treatment (prescribed by your doctor)
| Type | Standard Protocol | Eradication Rate |
|---|---|---|
| Hydrogen SIBO | Rifaximin 550 mg three times daily for 14 days | ~59% |
| IMO | Rifaximin + Neomycin 500 mg twice daily | ~87% |
| ISO | Rifaximin + bismuth subsalicylate + NAC | Under study |
| SIFO | Antifungals (fluconazole, nystatin) | Variable |
Rifaximin has the advantage of acting locally in the intestine with minimal systemic absorption, limiting side effects. NAC (N-acetylcysteine) is used in ISO to dissolve bacterial biofilms that protect sulfate-reducing bacteria.
7.2 Nutritional approach during treatment
Nutrition plays a crucial role during and after antibiotic treatment. Your dietitian will adapt your nutrition to:
- Support treatment effectiveness: certain dietary approaches enhance antimicrobial action
- Manage symptoms: reducing fermentable substrates during the acute phase
- Prevent deficiencies: targeted supplementation if needed
- Prepare for restoration: nutritional plan for the post-treatment reintroduction phase
8. Nutrition and SIBO: Food as a Therapeutic Tool
The nutritional approach to SIBO is never simply a list of foods to avoid. It is a personalized therapeutic strategy that evolves according to the phases of your care.
8.1 The low-fermentation approach
Temporary reduction of FODMAPs and fermentable substrates helps decrease gas production and relieve symptoms. This approach must always be:
- Temporary: a reduction phase followed by methodical reintroduction
- Personalized: each person reacts differently to different FODMAP groups
- Balanced: maintaining complete nutritional intake despite adaptations
- Enjoyable: identifying delicious alternatives for each adapted food
8.2 The low-sulfur approach for ISO
For patients with hydrogen sulfide overproduction, a diet adapted to reduce sulfur substrates has shown improvement in 73% of patients. Foods high in sulfur include certain cruciferous vegetables, eggs, garlic and onion — but the goal is never to permanently eliminate these foods, but rather to modulate them temporarily.
8.3 The elemental diet: an intensive option
The elemental diet consists of a completely pre-digested nutritional formula (amino acids, glucose, short-chain fatty acids) that is absorbed in the proximal duodenum, depriving bacteria of fermentable substrates. Studies report a success rate of 80% after 14 days. This is an intensive option that must be supervised by a nutrition professional.
8.4 Meal spacing: protecting the MMC
One of the simplest and most effective nutritional pillars:
- Space meals at least 4 to 5 hours apart to allow the MMC to function
- Eliminate snacking: each food intake interrupts the MMC
- 12-hour overnight fast: allow several complete MMC cycles during the night
Key insight: Meal spacing is one of the simplest and most effective strategies to support your natural "intestinal broom" (the MMC). Three balanced and satisfying meals, without snacking between meals, can make a significant difference in SIBO management.
9. Preventing Relapse: Long-Term Strategies
Relapse is a major challenge in SIBO management: studies show a relapse rate of 44% within 9 months and 27.5% within the first 6 months. This is why a long-term prevention strategy is essential.
9.1 Prokinetics: supporting motility
Prokinetics, prescribed by your doctor, stimulate the MMC and are the cornerstone of relapse prevention:
- Prucalopride: low dose in the evening, without the cardiac risks of older molecules, with neuro-regenerative properties
- Low-dose erythromycin: used as a motilin agonist (not as an antibiotic), can delay relapse by 5 months
- Low-dose naltrexone: 1.5-4.5 mg, immunomodulatory properties, particularly suited for autoimmune-origin SIBO
- Ginger extracts and herbal preparations: natural alternatives to support motility
9.2 Lifestyle: protective habits
- Meal spacing: minimum 4-5 hours between meals
- Overnight fasting: minimum 12 hours
- Stress management: chronic stress impairs motility via the gut-brain axis
- Regular physical activity: promotes intestinal motility
- Mindful eating: chew thoroughly, eat seated, without screens
9.3 Ongoing nutritional follow-up
Relapse prevention requires ongoing dietetic support. Your dietitian helps you to:
- Progressively reintroduce adapted foods
- Identify your personal triggers
- Maintain a varied and nutritionally complete diet
- Adjust your nutritional plan as your symptoms evolve
10. Cutting-Edge Research and Emerging Therapies
The field of SIBO is experiencing scientific momentum with several promising advances.
10.1 Targeted microbiomic therapies
The phase 2a clinical trial of EBX-102-02, a therapeutic microbial consortium, showed encouraging results: a reduction in the IBS Severity Scoring System (IBS-SSS) of 78 points compared to 53 for placebo, with the engraftment of more than 70 new beneficial bacterial species. This approach aims to restore microbial diversity rather than simply eliminating pathogens.
10.2 Specific methanogenesis inhibitors
CS-06 is a molecule in development that specifically blocks archaeal methanogenesis without disrupting the rest of the gut microbiome. This targeted approach could revolutionize IMO management.
10.3 Next-generation diagnostic tests
Next-generation sequencing (NGS) now enables detailed mapping of the small intestinal microbial communities, paving the way for truly personalized treatments based on each patient's individual microbial profile.
Key insight: Research is moving towards increasingly personalized approaches: rather than "one-size-fits-all" treatments, the future lies in precise identification of the type of overgrowth and treatment tailored to the individual microbial profile.
11. Our Personalized Approach at Diaeta
At Diaeta, we understand that SIBO is more than a diagnosis — it is a daily experience that affects your quality of life, your food choices and your overall wellbeing. Our approach is designed to support you at every stage of your journey towards digestive comfort.
What We Promise You
- Never hungry: even during dietary adaptation phases, your meals will be satisfying and satiating. We build nutritional plans that respect your appetite
- No unnecessary elimination: every adaptation is targeted, temporary and based on your individual tolerance. We systematically reintroduce foods as soon as possible
- Evidence-based advice: our approach is grounded in the latest scientific data on SIBO and its variants, not trends or fads
- Personalized strategies: your microbiome is unique, so is your nutritional plan. We adapt every recommendation to your specific profile
How We Support You
- Comprehensive Assessment: detailed analysis of your symptoms, medical history, dietary habits and test results
- Coordination with your gastroenterologist: teamwork to synchronize the nutritional approach with medical treatment
- Phase-based personalized nutritional plan: treatment phase, reintroduction phase, maintenance phase — each step is planned
- MMC optimization: establishing an eating rhythm that supports your natural intestinal motility
- Deficiency monitoring: surveillance and correction of SIBO-related nutritional deficits
Results Observed
With our personalized approach, our patients typically report:
- Significant reduction in bloating through precise identification of individual triggers
- Improved overall digestive comfort with a tailored and delicious meal plan
- Better energy and mental clarity through correction of nutritional deficiencies
- Lasting relapse prevention through personalized maintenance strategies
Do you suffer from chronic digestive symptoms and want to explore the SIBO path? Book an appointment for a personalized consultation in Brussels. Together, we will build a nutritional plan tailored to your unique situation.
Scientific References
- Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. Am J Gastroenterol. 2020;115(2):165-178.
- Rezaie A, Buresi M, Lembo A, et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017;112(5):775-784.
- Pimentel M, Morales W, Pokkunuri V, et al. Autoimmunity Links Vinculin to the Pathophysiology of Chronic Functional Bowel Changes Following Campylobacter jejuni Infection in a Rat Model. Dig Dis Sci. 2015;60(5):1195-1205.
- Ghoshal UC, Shukla R, Ghoshal U. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut Liver. 2017;11(2):196-208.
- Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome - An Update. Front Psychiatry. 2020;11:664.
- Pimentel M, Lembo A. Microbiome and Its Role in Irritable Bowel Syndrome. Dig Dis Sci. 2020;65(3):829-839.
- Quigley EMM. The Spectrum of Small Intestinal Bacterial Overgrowth (SIBO). Curr Gastroenterol Rep. 2019;21(1):3.
- Shah A, Talley NJ, Jones M, et al. Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies. Am J Gastroenterol. 2020;115(2):190-201.
- Losurdo G, Salvatore D'Abramo F, Indellicati G, et al. The Influence of Small Intestinal Bacterial Overgrowth in Digestive and Extra-Intestinal Disorders. Int J Mol Sci. 2020;21(10):3531.
- Souza C, Rocha R, Cotrim HP. Diet and intestinal bacterial overgrowth: Is there evidence? World J Clin Cases. 2022;10(13):4068-4075.
- Singer-Englar T, Rezaie A, Englar T, Pimentel M. Competitive hydrogen gas utilization by methane- and hydrogen sulfide-producing microorganisms and associated symptoms. Dig Dis Sci. 2023;68:263-272.
- Pimentel M, et al. EBX-102-02 Phase 2a Trial Results for IBS with Diarrhea. Gastroenterology. 2025;168(4):S-123.
