NutriMedX – Functional and Regenerative Medicine

From Dysbiosis, SIBO and Helicobacter pylori to Personalized Nutritional Medicine

Abdominal bloating is one of the most common digestive symptoms encountered in medical practice. For some patients, it is an occasional, transient discomfort related to diet or meal timing. For others, however, it becomes a chronic, recurrent and disabling symptom, with a significant impact on quality of life, eating behavior and social activities.

Although it is often rapidly classified as a functional digestive disorder, persistent bloating should not be regarded as a diagnosis in itself. Rather, it represents a symptom-syndrome located at the intersection of microbiota, motility, fermentation, visceral sensitivity, intestinal permeability, low-grade inflammation and eating behavior.

In clinical practice, chronic bloating may reflect multiple mechanisms: intestinal dysbiosis, small intestinal bacterial overgrowth — SIBO, intestinal methanogen overgrowth — IMO, active or incompletely eradicated Helicobacter pylori infection, motility disorders, food intolerances, biliary dysfunction, digestive enzyme insufficiency, visceral hypersensitivity or disturbances of the gut-brain axis.

Therefore, an effective approach cannot be reduced to the empirical elimination of certain foods or to the non-specific administration of probiotics. It requires the identification of the dominant mechanism and the construction of a personalized therapeutic plan.

Bloating versus Abdominal Distension

From a clinical perspective, it is important to distinguish between bloating and abdominal distension.

Bloating is the subjective sensation of fullness, pressure or abdominal tension, without necessarily involving an objective change in abdominal circumference.

Abdominal distension refers to a measurable or visible increase in abdominal circumference, which can be clinically or imagistically objectified.

The two manifestations frequently coexist, but they are not synonymous. Some patients describe severe bloating without objective distension, suggesting an important component of visceral hypersensitivity. Others present visible distension, especially postprandially or in the evening, which may point toward gas accumulation, dysmotility, constipation, excessive fermentation or abnormal abdomino-phrenic accommodation.

This distinction has important diagnostic and therapeutic implications.

Clinical Impact and Quality of Life

Chronic bloating frequently affects patients with irritable bowel syndrome, functional dyspepsia, chronic constipation or bowel habit disorders. However, it may also occur independently of these diagnoses.

Its impact on quality of life is often underestimated. Patients avoid meals in social contexts, eliminate certain foods, develop anticipatory anxiety related to eating and sometimes adopt highly restrictive diets. Over time, this behavior may reduce dietary diversity, further disrupt the gut microbiota and transform food into an additional source of stress.

For this reason, chronic bloating should not be minimized. The fact that it is common does not mean that it is trivial.

Pathophysiological Mechanisms Involved

Chronic bloating is not a single-mechanism phenomenon. In most cases, the symptom arises from the overlap of several mechanisms.

1. Excessive Fermentation and Gas Production

Intestinal gases result mainly from bacterial fermentation of undigested or incompletely absorbed dietary substrates. Fermentable carbohydrates, fibers, polyols and, under certain conditions, proteins may become substrates for the production of hydrogen, methane or hydrogen sulfide.

The amount and type of gases produced depend on the composition of the microbiota, intestinal transit time, the patient’s diet and the colon’s ability to absorb or evacuate gases.

In particular, increased methane production, associated with intestinal methanogen overgrowth, is correlated with slower transit and constipation. Thus, the patient with bloating, constipation and marked abdominal distension may have a different pathophysiological profile from the patient with bloating and diarrhea.

2. Intestinal Dysmotility

Inefficient gas evacuation may be just as important as excessive gas production. Intestinal motility disorders favor the stagnation of intestinal contents, prolonged fermentation and gas accumulation.

The migrating motor complex, active during interdigestive periods, has the role of clearing the small intestine of food residues and bacteria. Its dysfunction may favor the development of SIBO and the onset of rapid postprandial symptoms.

Colonic dysmotility, especially in the context of chronic constipation, prolongs the contact time between dietary substrate and microbiota, amplifying fermentation and distension.

3. Visceral Hypersensitivity

Not all patients with bloating produce excessive gas. In some, the main problem is an amplified perception of intestinal distension. These patients have a low threshold for visceral perception and may experience minimal distension as intensely painful or uncomfortable.

Visceral hypersensitivity involves changes in the gut-brain axis, central sensitization and abnormal processing of visceral afferent signals. Chronic stress, anxiety, sleep disturbances and repeated digestive symptom experiences may amplify this perception.

This component should not be interpreted as an “imaginary symptom.” On the contrary, visceral hypersensitivity is a real physiological mechanism, even if it is not visible on ultrasound or endoscopy.

4. Intestinal Dysbiosis

The gut microbiome plays a central role in digestion, immunity, metabolism, the synthesis of certain metabolites and the maintenance of the intestinal barrier. Imbalance of this ecosystem — dysbiosis — may contribute to bloating through several mechanisms:

reduced microbial diversity, decreased butyrate-producing bacteria, increased species involved in excessive fermentation, altered bile acid metabolism, low-grade inflammation and changes in visceral sensitivity.

A microbiome deficient in short-chain fatty acid-producing bacteria, particularly butyrate producers, may impair the integrity of the intestinal barrier and the regulation of the local inflammatory response. At the same time, the predominance of certain fermentative profiles may accentuate gas production and postprandial symptoms.

Microbiome testing may provide useful information, but it should not be interpreted in isolation. There is no simple list of “good” and “bad” bacteria that can fully explain a patient’s symptoms. The clinical value of testing increases when the result is integrated with the patient’s history, actual diet, bowel habits, antibiotic exposure, inflammatory markers and response to interventions.

5. SIBO and IMO

SIBO — small intestinal bacterial overgrowth — refers to bacterial overgrowth in the small intestine, with early fermentation of dietary substrate in a segment where digestion and absorption should normally predominate.

Clinically, SIBO may cause rapid bloating after meals, gas, abdominal pain, diarrhea, constipation or alternating bowel habits. Depending on the predominant gases, the clinical phenotype differs. Hydrogen is more frequently associated with diarrhea, whereas methane is associated with constipation and slower transit.

Currently, methanogen overgrowth is often classified separately as IMO — intestinal methanogen overgrowth — because methanogens are not bacteria but archaea, and their location may be both in the small intestine and in the colon.

Breath tests with glucose or lactulose are used in clinical practice, but they must be interpreted with caution. The result may be influenced by patient preparation, orocecal transit time, the substrate used and the gas pattern. The diagnosis should not be based on the test alone, but on clinical integration.

6. Intestinal Permeability and Low-Grade Inflammation

The intestinal barrier consists of epithelium, tight junctions, mucus layer, immune components and microbiota. When this barrier is impaired, the contact between the immune system and food antigens, bacterial metabolites and microbial components increases.

Increased intestinal permeability is increasingly discussed in the context of functional digestive disorders, metabolic diseases and chronic low-grade inflammation. However, the markers used for its assessment must be interpreted with caution. Tests such as zonulin, fecal alpha-1 antitrypsin or other barrier markers may be useful in certain contexts, but they should not be considered stand-alone diagnostic tools.

Clinically, impaired intestinal barrier function may be associated with multiple food intolerances, mucosal inflammation, dysbiosis, visceral sensitivity and incomplete therapeutic response to strictly dietary interventions.

7. Dietary Factors

Diet directly influences bloating through the amount and type of fermentable substrate ingested. FODMAPs — fermentable oligosaccharides, disaccharides, monosaccharides and polyols — are poorly absorbed in the small intestine and may become substrates for bacterial fermentation.

A low-FODMAP diet may be useful in selected patients, especially in irritable bowel syndrome or excessive fermentation. However, it should not become a permanent diet. Correct use involves a limited reduction phase, followed by gradual reintroduction in order to identify individual tolerance.

Prolonged restrictive diets may reduce dietary diversity, increase anxiety around food and contribute to nutritional imbalances. The objective is not to keep the patient on a narrow list of “allowed” foods, but to restore digestive tolerance.

The Role of Helicobacter pylori Infection

Helicobacter pylori infection remains a major cause of chronic gastritis, peptic ulcer disease and increased gastric cancer risk. In clinical practice, patients with active infection or a history of treatment for H. pylori may present with dyspepsia, reflux, nausea, postprandial fullness and bloating.

Persistence of symptoms after treatment should not be interpreted simplistically. Eradication must be confirmed using appropriate methods, but associated imbalances should also be evaluated: post-antibiotic dysbiosis, inefficient digestion, SIBO, persistent gastric inflammation, secondary food sensitivity or motility disorders.

In this sense, H. pylori may be part of a broader digestive context. Eradication of the infection is important, but it does not always fully resolve symptoms if the microbiome, motility and diet remain unaddressed.

Differential Diagnosis

The evaluation of a patient with chronic bloating should begin with a detailed history: symptom onset, relation to meals, types of foods involved, bowel habits, antibiotic history, chronic medications, surgical history, stress, sleep, family history and alarm symptoms.

The differential diagnosis includes:

Functional digestive disorders: irritable bowel syndrome, functional bloating/distension, functional dyspepsia.

Motility disorders: chronic constipation, altered orocecal transit, gastroparesis, postsurgical dysfunctions.

Microbial causes: SIBO, IMO, colonic dysbiosis, post-antibiotic dysbiosis.

Inflammatory and immune causes: celiac disease, inflammatory bowel disease, enteropathies, histamine intolerance, mast cell activation in selected cases.

Infectious causes: Helicobacter pylori, parasitic infections, recurrent gastrointestinal infections.

Metabolic and endocrine causes: hypothyroidism, diabetes mellitus with dysmotility, exocrine pancreatic insufficiency.

Dietary causes: excess FODMAPs, polyols, alcohol, ultra-processed foods, irregular meals, inadequate fiber intake or fibers introduced inappropriately.

Useful Investigations

There is no universal panel for bloating. Investigations should be individualized according to the clinical picture.

In medical practice, the following may be useful:

complete blood count, ESR, CRP, ferritin, liver profile, fasting glucose and HbA1c, TSH, vitamin B12, folate, vitamin D, albumin, anti-tissue transglutaminase IgA antibodies and total IgA for celiac disease, fecal calprotectin when intestinal inflammation is suspected, testing for H. pylori, breath tests for SIBO/IMO and food intolerances, fecal pancreatic elastase when exocrine pancreatic insufficiency is suspected, stool parasitology in selected contexts and intestinal microbiome testing when the result can guide nutritional and therapeutic intervention.

Upper gastrointestinal endoscopy, colonoscopy or abdominal imaging should be indicated according to age, alarm symptoms, family history, biological abnormalities or lack of response to initial interventions.

Therapeutic Principles

The treatment of chronic bloating must be personalized and oriented toward the dominant mechanism. There is no universal diet, no universal probiotic and no identical therapeutic protocol for all patients.

1. Dietary Intervention

The first step is the analysis of the patient’s real diet: meal timing, food volume, amount of sugar, alcohol, ultra-processed foods, fibers, dairy products, fruit, legumes, sweeteners, carbonated drinks and food combinations.

In patients with suggestive symptoms, temporary reduction of FODMAPs may be useful, provided that gradual reintroduction follows. In patients with lactose, fructose or sorbitol intolerance, the intervention should be adapted to test results and individual tolerance.

Gluten exclusion should be reserved for patients with celiac disease, wheat allergy or clinically supported non-celiac gluten sensitivity, not applied automatically to all patients with bloating.

2. Treatment of SIBO/IMO

In confirmed or strongly suspected cases, treatment of SIBO/IMO may include antimicrobial therapy, interventions targeting motility, correction of predisposing factors and temporary nutritional adjustments.

Non-absorbable antibiotics, combined therapies in methane-predominant forms and botanical antimicrobial agents may be options in selected cases, but they must be used in a medical context, with monitoring of response and prevention of recurrence.

Restoring motility is essential, because SIBO recurrence is frequent when the predisposing mechanism remains active. Prokinetics, meal hygiene, spacing of meals and correction of constipation may play an important role.

3. Digestive Support

In patients with inefficient digestion, postprandial fullness, steatorrhea, enzyme deficiency or poor tolerance to meals, digestive enzymes, biliary support or evaluation of exocrine pancreatic function may be useful.

The aim is to reduce the undigested food substrate that reaches bacterial fermentation and to improve postprandial symptoms.

4. Restoration of the Intestinal Barrier

In patients with signs of mucosal inflammation, significant dysbiosis, multiple intolerances or post-infectious/post-antibiotic symptoms, restoration of the intestinal barrier may be an important component.

Interventions may include correction of nutritional deficiencies, gradual increase in dietary diversity, and selective use of prebiotics, probiotics, polyphenols, butyrate or other nutrients with trophic effects on the intestinal mucosa. The choice must be individualized, because introducing fibers or prebiotics too rapidly may worsen bloating in patients with excessive fermentation.

5. Modulation of the Microbiota

Probiotics may be useful in certain clinical phenotypes, but they should not be administered non-specifically. The choice of strain, dose and timing matters.

A patient with active SIBO, elevated histamine, severe constipation or intense fermentation may react unfavorably to certain probiotics. Conversely, in selected patients, specific strains may reduce inflammation, support the intestinal barrier and improve transit.

Prebiotics should be introduced progressively, according to tolerance.

6. The Gut-Brain Axis

In patients with an important component of visceral hypersensitivity, a strictly digestive approach may be insufficient. Sleep, chronic stress, anxiety, previous negative digestive experiences, hypervigilance toward symptoms and dysfunction of the gut-brain axis may perpetuate symptoms.

In such cases, therapies aimed at regulating the gut-brain axis, cognitive behavioral therapy, gut-directed hypnotherapy, stress reduction techniques and, in selected cases, neuromodulatory medication may have a therapeutic role.

Alarm Signs

Chronic bloating requires prompt investigation when associated with:

new onset after the age of 50, unintentional weight loss, anemia, rectal bleeding or melena, fever, night sweats, persistent vomiting, dysphagia, nocturnal pain, deterioration of general condition, palpable abdominal mass, significantly elevated fecal calprotectin, family history of colorectal cancer or inflammatory bowel disease.

In these situations, colonoscopy, upper gastrointestinal endoscopy and/or abdominal imaging should be considered without delay.

Conclusions

Chronic bloating is not a trivial symptom and should not be reduced to a simple consequence of stress or diet. In many cases, it represents the clinical expression of a complex digestive imbalance involving intestinal dysbiosis, SIBO, IMO, dysmotility, increased intestinal permeability, Helicobacter pylori infection, visceral hypersensitivity and changes in the gut-brain axis.

The modern approach to the patient with persistent bloating must be stepwise, rational and personalized: exclusion of alarm signs, identification of the dominant mechanism, targeted testing and therapeutic intervention adapted to the clinical context.

The label “functional” should not be used as a synonym for “unexplained” or “untreatable.” Functional does not mean imaginary. It means that the mechanism is real, even if it is not always visible on ultrasound or endoscopy.

By integrating clinical, biological, nutritional and microbiome data, chronic bloating can be understood not merely as a symptom, but as an indicator of the loss of balance within the digestive ecosystem.

Selected References

• Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. American Journal of Gastroenterology. 2020.
• Malfertheiner P, Megraud F, Rokkas T, et al. Management of Helicobacter pylori infection: the Maastricht VI/Florence consensus report. Gut. 2022.
• Vasant DH, Paine PA, Black CJ, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021.
• Lacy BE, Cangemi D, Vazquez-Roque M. Management of chronic abdominal bloating and distension. Clinical Gastroenterology and Hepatology.
• Rome Foundation. Rome IV Criteria: Functional Gastrointestinal Disorders.