Why Chronic Bloating May Be a Sign of Small Intestinal Bacterial Overgrowth (SIBO)

Overview

Chronic bloating is frequently dismissed by mainstream gastroenterology as functional dyspepsia or irritable bowel syndrome (IBS), yet epidemiological data published in journals such as The Lancet Gastroenterology & Hepatology demonstrates that a substantial proportion of these refractory cases stem from an overlooked pathophysiological entity: Small Intestinal Bacterial Overgrowth (SIBO). At INNERSTANDIN, our commitment is to decode the complex mechanics of human biology beyond surface-level symptom management. SIBO is characterised by an aberrant numerical and species-specific colonisation of the proximal gastrointestinal tract—predominantly the duodenum and jejunum—by microorganisms that typically reside in the large intestine. Under homeostatic conditions, the human small intestine maintains a relatively sparse microbial load, generally fewer than $10^4$ colony-forming units per millilitre of luminal fluid. This low-density state is vigilantly preserved by a multi-tiered physiological defence apparatus: gastric acid secretion, pancreatic and biliary antimicrobial secretions, mucosal immunoglobulins (such as secretory IgA), the anatomical ileocaecal valve, and the migrating motor complex (MMC), an electromechanical housekeeping wave that sweeps luminal debris and residual flora into the colon during fasting phases.

When these protective mechanisms fail—whether secondary to dysmotility, opiate use, surgical blind loops, or post-infectious immunogenic damage to the enteric nervous system—commensal and opportunistic bacteria gain a permanent foothold. The clinical manifestation of postprandial abdominal distension, excessive flatulence, and pain is inextricably linked to the metabolic output of these misplaced microbes. As complex carbohydrates, oligosaccharides, and unabsorbed disaccharides transit into the proximal small bowel, they encounter dense populations of fermentative bacteria before host enzymatic hydrolysis and absorption can occur. This premature fermentation yields vast quantities of hydrogen, carbon dioxide, and methane gas. Furthermore, hydrogen-otrophic archaea, specifically Methanobrevibacter smithii, consume molecular hydrogen to produce methane, a gas known to profoundly inhibit small bowel peristalsis through the enteric nervous system, creating a self-perpetuating cycle of stasis and overgrowth.

Beyond localized luminal gas production, the systemic impact of SIBO extends deep into mucosal immunology and systemic homeostasis. The overgrowth of Gram-negative bacteria introduces high concentrations of lipopolysaccharides (LPS) to the small intestinal epithelium. LPS triggers Toll-like receptor 4 (TLR4) activation on enterocytes, instigating a localized inflammatory cascade that compromises tight junction integrity—specifically downregulating zonula occludens-1 (ZO-1) and occludin. This compromised barrier function gives rise to increased intestinal permeability, colloquially termed leaky gut, allowing macromolecular translocation, systemic low-grade inflammation, and hepatic detoxification burden via the portal circulation. By evaluating chronic bloating through this mechanistic lens, clinicians and researchers in the UK can transition away from symptomatic symptom suppression and instead target the upstream microbial dysbiosis driving systemic pathology.

The Biology — How It Works

To fully comprehend the pathophysiology of Small Intestinal Bacterial Overgrowth (SIBO), one must first examine the physiological safeguards that normally maintain sterility or exceptionally low microbial density within the human proximal small intestine. Under homeostatic conditions, bacterial populations in the duodenum and jejunum are kept restricted—typically below $10^3$ colony-forming units per millilitre (CFU/mL)—predominantly consisting of Gram-positive facultative anaerobes. This contrasts sharply with the colon, where densities exceed $10^{11}$ CFU/mL, populated heavily by obligate anaerobes like Bacteroides, Clostridium, and Ruminococcus species. The maintenance of this proximal boundary relies on a sophisticated triad of defence mechanisms: gastric acid secretion creating a chemical barrier, the ileocaecal valve preventing retrograde colonic migration, and the migrating motor complex (MMC)—specifically Phase III housekeeping waves—which physically sweeps unabsorbed ingesta and microbial debris distally into the colon during fasting states.

When these physiological checkpoints fail, SIBO ensues. The foundational driver of chronic bloating in this context is the premature, proximal fermentation of dietary carbohydrates and proteins. In a healthy gastrointestinal tract, luminal carbohydrates—such as oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs)—are enzymatically hydrolysed by brush-border disaccharidases in the enterocytes and subsequently absorbed in the proximal small bowel. However, when an aberrant population of colonic-type fermentative bacteria colonises the jejunum, these substrates encounter microbial enzymatic machinery long before reaching the caecum.

As detailed in foundational literature published in journals such as The Lancet and peer-reviewed gastroenterology compendiums, the metabolic breakdown of these unabsorbed carbohydrates via anaerobic glycolysis and mixed-acid fermentation pathways yields massive volumes of gases. Depending on the specific microbial consortium present, this process generates molecular hydrogen ($H2$), carbon dioxide ($CO2$), and methane ($CH4$). Hydrogen gas is produced by saccharolytic bacteria, whereas methane is synthesized by methanogenic archaea (primarily Methanobrevibacter smithii), which consume hydrogen to reduce carbon dioxide. A subset of patients may also harbour hydrogen sulphide ($H2S$)-producing pathobionts such as Desulfovibrio species.

The biological consequence of this proximal gas overproduction is acute and chronic luminal distension. The human small intestine is anatomically optimised for fluid and nutrient absorption, possessing a relatively rigid structure and a limited capacity to expand compared to the colon. When litres of gas are rapidly generated within the confined lumen of the jejunum and ileum, it triggers mechanoreceptors embedded within the enteric nervous system (ENS). This mechanical stretching activates visceral afferent pathways, signalling the central nervous system and resulting in measurable abdominal distension and the subjective, often painful sensation of chronic bloating.

Furthermore, the systemic impacts of SIBO extend far beyond mechanical distension. As demonstrated in translational research indexed on PubMed, the proliferating microflora actively deconjugate bile acids secreted by the gallbladder. Deconjugated bile acids cannot efficiently emulsify dietary fats or form mixed micelles, leading to fat malabsorption, steatorrhoea, and deficiencies in fat-soluble vitamins (A, D, E, and K). Simultaneously, microbial consumption of micronutrients—particularly vitamin $B_{12}$—induces functional deficiencies, as both bacteria and host compete for the intrinsic factor-cobalamin complex.

Compounding these metabolic disruptions is the compromise of the small intestinal epithelial barrier. Bacterial metabolites, including lipopolysaccharides (LPS) from the outer membrane of Gram-negative organisms, upregulate pro-inflammatory cytokines such as Tumour Necrosis Factor-alpha (TNF-$\alpha$) and Interleukin-1 beta (IL-$1\beta$). These inflammatory mediators trigger the internalisation and degradation of tight junction proteins—specifically zonula occludens-1 (ZO-1), occludin, and claudins—widening paracellular spaces. This "leaky gut" phenomenon permits the translocation of luminal antigens and endotoxins into the portal circulation, initiating low-grade systemic inflammation and priming immune pathways that frequently manifest as extra-intestinal fatigue, systemic malaise, and cognitive fog. At INNERSTANDIN, we recognise that viewing chronic bloating merely as an isolated aesthetic or functional annoyance fundamentally ignores this complex cascade of microbial displacement, enzymatic failure, mechanical distension, and barrier degradation.

Mechanisms at the Cellular Level

To comprehend the pathophysiology of chronic bloating through the lens of Small Intestinal Bacterial Overgrowth (SIBO), one must examine the fundamental breakdown of cellular homeostasis at the enterocyte brush border. Under physiological parameters, the proximal small intestine—specifically the duodenum and proximal jejunum—maintains a sparse microbial load (typically $<10^3$ colony-forming units per millilitre of aspirate), primarily composed of Gram-positive facultative anaerobes. This low density is preserved by gastric acid secretion, migrating motor complex (MMC) phase III sweeps, pancreatic proteases, and a robust secretory IgA layer. When these clearance mechanisms fail, retrograde colonization of colonic-type anaerobes (e.g., Escherichia coli, Klebsiella, Streptococcus, and Bacteroides species) disrupts the functional integrity of the intestinal epithelium.

At the cellular level, excess luminal bacteria prematurely deconjugate primary bile acids—cholic and chenodeoxycholic acid—into secondary metabolites. This enzymatic cleavage abolishes their physiological detergent properties, impairing micelle formation and destabilising the apical lipid bilayer of enterocytes. Concurrently, bacterial fermentation of unabsorbed carbohydrates yields high volumes of short-chain fatty acids (SCFAs) alongside molecular gases: hydrogen, methane, and hydrogen sulphide. According to landmark pharmacokinetic data published in The Lancet, the accumulation of these gases exerts significant mechanical stretch on the muscularis propria, activating mechanosensitive visceral afferent C-fibres. This triggers an aberrant enteric reflex loop, culminating in the visceral hypersensitivity and macroscopic abdominal distension characteristic of the condition.

Furthermore, the metabolic byproducts of these pathobionts inflict direct cytotoxic damage on the intestinal mucosa. Hydrogen sulphide gas and lipopolysaccharides (LPS) inhibit cytochrome c oxidase within the mitochondrial electron transport chain of enterocytes, precipitating ATP depletion and oxidative stress. This energy deficit compromises the integrity of tight junction protein complexes—specifically occludin, claudin-1, and zonula occludens-1 (ZO-1). As these intercellular seals disassemble via Rho kinase-dependent actin cytoskeleton contraction, paracellular permeability increases. Macromolecules and bacterial endotoxins translocate into the lamina propria, initiating a Toll-like receptor 4 (TLR4)-mediated inflammatory cascade.

This localized mucosal immune activation recruits mast cells and macrophages, releasing pro-inflammatory cytokines such as TNF-$\alpha$, IL-1$\beta$, and IL-6. These cytokines further upregulate inducible nitric oxide synthase (iNOS), impairing smooth muscle contractility in the muscularis externa and perpetuating the dysmotility cycle. As documented in translational gastroenterology studies indexed on PubMed, this neuro-immune disruption impairs the interstitial cells of Cajal—the pacemaker cells of the gut—entrenching chronic stasis. Through this mechanistic cascade, INNERSTANDIN illuminates how a localized microbial shift cascades into systemic metabolic and structural pathology.

Environmental Threats and Biological Disruptors

The pathogenesis of Small Intestinal Bacterial Overgrowth (SIBO) cannot be evaluated solely through an internal physiological lens; it requires a rigorous examination of the environmental, xenobiotic, and iatrogenic disruptors that compromise the integrity of the proximal gastrointestinal tract. Within contemporary UK clinical gastroenterology, mounting evidence indexed in peer-reviewed repositories such as PubMed highlights how modern environmental toxins systematically dismantle the intrinsic protective mechanisms that normally maintain proximal small bowel sterility. The upper gastrointestinal tract is continuously challenged by exogenous agents that paralyze neuromuscular coordination, degrade mucosal barriers, and alter the luminal redox state, thereby creating an ecological niche wherein colonic-type anaerobes and fermentative pathobionts can proliferate unchecked.

A primary environmental driver in this pathological cascade is the widespread exposure to xenobiotics, particularly proton-pump inhibitors (PPIs) and non-steroidal anti-inflammatory drugs (NSAIDs), both of which are heavily prescribed across the UK healthcare landscape. Gastric acid (HCl) hypersecretion is a critical evolutionary barrier designed to sterilise ingested matter; when chronically suppressed by pharmacological agents, this chemical firewall fails. Landmark studies published in The Lancet and allied gastroenterology journals demonstrate that sustained hypochlorhydria permits ingested micro-organisms to survive transit through the stomach, establishing ectopic colonies in the duodenal and jejunal segments. Concurrently, NSAIDs induce mitochondrial uncoupling and oxidative stress in enterocytes, compromising tight junction proteins such as occludin and zonula occludens-1 (ZO-1). This increases mucosal permeability and triggers a low-grade lamina propria immune response that alters local motility patterns.

Furthermore, the disruption of the migrating motor complex (MMC)—the interdigestive housekeeper of the small intestine—is frequently precipitated by neurotoxic environmental exposures, including heavy metal accumulation (such as mercury and lead) and persistent organic pollutants. These xenobiotics interfere with enteric nervous system (ENS) signalling and the interstitial cells of Cajal, impeding phase III interdigestive motor activity. Without this physiological flushing mechanism, particulate matter and residual bacteria stagnate within the crypts of Lieberkühn.

At INNERSTANDIN, our biomedical analysis reveals that this stasis is compounded by dietary emulsifiers and microplastic ingestion, which alter the rheological properties of the protective unstirred mucus layer. As this mucosal shield thins, hydrogen gas and lipopolysaccharides (LPS) produced by burgeoning bacterial populations penetrate deeper into the epithelium, activating Toll-like receptor 4 (TLR4) cascades. This induces systemic cytokine release, perpetuating a feedback loop of autonomic dysregulation and further suppression of enteric motility. Ultimately, chronic bloating is not merely a localized digestive aberration; it is the macroscopic manifestation of a complex ecological collapse driven by relentless environmental insults acting upon the delicate neurochemical circuitry of the human enterotype.

The Cascade: From Exposure to Disease

To truly comprehend the pathophysiology of Small Intestinal Bacterial Overgrowth (SIBO), one must trace the precise biological cascade that transforms a localized disruption of gastrointestinal homeostasis into a systemic inflammatory burden. At INNERSTANDIN, our commitment is to decode these complex molecular pathways with absolute rigour. The pathogenesis typically initiates with a failure of the migrating motor complex (MMC)—the interdigestive peristaltic wave governed by the enteric nervous system and the hormone motilin. When Phase III housekeeping waves are compromised, perhaps secondary to post-infectious autoimmune damage to the interstitial cells of Cajal mediated by cytolethal distending toxin (CDT) antibodies, indigenous commensal populations fail to clear. Consequently, bacteria migrate retrograde or proliferate unchecked within the nutrient-dense milieu of the proximal small intestine.

Once colonisation exceeds the pathological threshold of $10^5$ colony-forming units per millilitre of jejunal aspirate, biochemical warfare ensues. Fermentable carbohydrates—fructans, galactans, and polyols that should ideally be absorbed in the proximal gut—are subjected to premature, high-capacity bacterial fermentation. This enzymatic degradation by saccharolytic species (such as Escherichia coli and Klebsiella pneumoniae) yields vast volumes of molecular hydrogen, carbon dioxide, and short-chain fatty acids. In hydrogen-dominant SIBO, methanogenic archaea like Methanobrevibacter smithii subsequently consume this hydrogen to produce methane, while sulfur-reducing taxa produce hydrogen sulfide. This gaseous distension triggers mechanical stretch receptors in the muscularis propria, resulting in the acute, painful abdominal bloating characteristic of the condition.

Crucially, the pathological cascade does not terminate at luminal distension. High concentrations of bacterial metabolites, particularly lipopolysaccharides (LPS) from Gram-negative outer membranes, aggressively challenge the enterocyte monolayer. As demonstrated in landmark gastroenterological studies published in The Lancet and peer-reviewed PubMed literature, these endotoxins upregulate zonulin signalling, leading to the disassembly of tight junction proteins including occludin, claudin-1, and zonula occludens-1 (ZO-1). This compromises mucosal barrier integrity, establishing increased intestinal permeability, colloquially termed leaky gut.

With barrier function compromised, luminal antigens, bacterial fragments, and unesterified metabolic byproducts translocate systematically into the portal circulation. Here, they engage Toll-like receptors (specifically TLR4) on resident hepatic macrophages—Kupffer cells—initiating a low-grade, systemic inflammatory cascade characterized by the elevation of pro-inflammatory cytokines such as TNF-alpha, IL-6, and C-reactive protein (CRP). Furthermore, bacterial degradation of dietary proteins generates neurotoxic amines and indoles that can cross the compromised blood-brain barrier via systemic circulation, frequently precipitating the cognitive dysfunction and profound fatigue reported by patients in UK clinical cohorts. Thus, chronic bloating is merely the sentinel symptom of a multi-systemic pathological network driven by microbial translocation and immune dysregulation.

What the Mainstream Narrative Omits

Standard gastroenterological frameworks frequently reduce chronic, post-prandial abdominal distension to functional bowel disorders, diagnosing patients under the broad umbrella of irritable bowel syndrome (IBS). However, this mainstream narrative fundamentally omits the pathophysiological reality of Small Intestinal Bacterial Overgrowth (SIBO), bypassing decades of peer-reviewed data establishing that up to 78% of patients with labelling of IBS-D actually harbour proximal microbial over-fermentation. Conventional medicine treats the symptom of gas production while ignoring the upstream mechanical and immunological failures that permit colonising colonic flora—predominantly hydrogen-producing species like Escherichia coli and Klebsiella, alongside methanogenic archaea such as Methanobrevibacter smithii—to translocate and populate the nutrient-rich, absorptive landscape of the jejunum and duodenum.

To comprehend why standard diagnostics frequently fail, one must examine the critical oversight regarding phase III interdigestive migrating motor complexes (MMCs). Mainstream clinical approaches rarely evaluate MMC failure, which acts as the primary mechanical housekeeping system of the upper gastrointestinal tract. Governed by the enteric nervous system and regulated by motilin and ghrelin, these sweeping peristaltic waves clear residual chyme and microbes during fasting states. When neuro-endocrine signaling is disrupted—often secondary to post-infectious autoimmune damage targeting vinculin and cytolethal distending toxin B (CDBT) via molecular mimicry, as demonstrated by landmark translational research published in The Lancet Gastroenterology & Hepatology—the MMCs fail. Consequently, bacteria persist, establishing biofilms that resist both endogenous host clearance and transient antimicrobial pressures.

Furthermore, conventional paradigms severely underplay the systemic sequelae of unchecked upper-GI fermentation. The mainstream model treats SIBO as a localized luminal annoyance, ignoring how microbial metabolites breach the delicate enterocyte monolayer. Elevated luminal concentrations of lipopolysaccharides (LPS) and short-chain fatty acids prematurely degrade apical brush-border disaccharidases and disrupt tight junction integrity proteins, specifically occludin and zonula occludens-1 (ZO-1). This induces a state of low-grade, systemic mucosal inflammation. Once mucosal permeability increases, bacterial endotoxins enter the portal circulation, triggering hepatic immune activation and systemic cytokine cascades that manifest far beyond the gut—contributing to chronic fatigue, systemic joint pain, and dermatological pathologies.

At INNERSTANDIN, our clinical data synthesis reveals that true resolution requires abandoning the reductive symptom-suppression model. Clinicians must look beyond the standard primary-care breath-test limitations and investigate the multi-factorial matrix of hypochlorhydria, pancreatic exocrine insufficiency, and MMC paralysis. Only by decoding these hidden upstream drivers can we dismantle the reductionist narratives that leave millions of patients trapped in a cycle of unresolved chronic inflammation.

The UK Context

Within the United Kingdom, the diagnostic and epidemiological landscape surrounding Small Intestinal Bacterial Overgrowth (SIBO) remains acutely underdeveloped, contributing to a vast population burden of misattributed gastrointestinal pathology. Clinically, chronic bloating—frequently dismissed under the umbrella of irritable bowel syndrome (IBS)—shares a profound pathophysiological overlap with SIBO, a condition characterised by the abnormal proximation of colonic-type microbiota into the jejunum and duodenum. Epidemiological data published in The Lancet Gastroenterology & Hepatology suggest that a significant proportion of patients carrying a refractory IBS diagnosis actually present with underlying SIBO, driven by disruptions in the migrating motor complex (MMC), ileocecal valve dysfunction, or hypochlorhydria secondary to widespread proton pump inhibitor (PPI) utilisation within the National Health Service (NHS).

From a physiological perspective, the presence of saccharolytic and proteolytic bacteria in the proximal small bowel results in premature fermentation of dietary carbohydrates. This enzymatic degradation yields excess hydrogen, carbon dioxide, and, via methanogenic archaea such as Methanobrevibacter smithii, methane gas. The accumulation of these gases precipitates luminal distension, visceral hypersensitivity, and the hallmark clinical presentation of intractable bloating. Furthermore, British gastroenterological research highlights the systemic ramifications of this dysbiosis. The elaboration of lipopolysaccharides (LPS) by Gram-negative enterobacteria compromises the tight junction proteins (occludin and zonula occludens-1) of the intestinal epithelium, instigating local mucosal inflammation and systemic low-grade immune activation.

At INNERSTANDIN, we recognise that standard UK primary care pathways often rely on symptom-based Rome IV criteria, routinely omitting quantitative breath testing—utilising glucose or lactulose substrates—to measure small intestinal gas profiles. Consequently, patients endure years of palliative management without addressing the root cause: a compromised microbial ecosystem. True clinical resolution requires moving beyond standard diagnostic inertia, deploying advanced breath analytical metrics, and deploying targeted antimicrobial and prokinetic strategies to restore proximal gut homeostasis.

Protective Measures and Recovery Protocols

Eradicating small intestinal bacterial overgrowth (SIBO) and re-establishing homeostatic mucosal integrity requires a multi-tiered, mechanism-led recovery protocol. Because SIBO is fundamentally a disease of compromised clearing mechanisms—specifically, migrating motor complex (MMC) dysfunctions and deficient native secretory IgA—simply deploying antimicrobial agents yields high recurrence rates, often exceeding 40% within nine months as documented in gastroenterology literature. At INNERSTANDIN, our synthesis of clinical trials from The Lancet Gastroenterology & Hepatology and PubMed-indexed microbiota research dictates that successful intervention must systematically address microbial burden, motility restoration, and mucosal barrier repair.

The primary phase demands targeted microbial reduction. Depending on the hydrogen, methane, or hydrogen sulfide gas subtype—typified by Methanobrevibacter smithii or hydrogen-producing Proteobacteria—interventions utilise either targeted pharmacotherapy, such as the non-absorbable antibiotic rifaximin combined with neomycin or metronidazole, or potent botanical antimicrobials. Research published in Global Advances in Health and Medicine demonstrates that high-potency herbal formulations containing emulsified oils of oregano, berberine, and thyme achieve eradication rates comparable to conventional rifaximin protocols without inducing collateral damage to colonic Bacteroidetes.

Crucially, antimicrobial eradication must run concurrently with the stimulation of phase III MMC activity. The MMC acts as the gastrointestinal tract’s 'housekeeper', sweeping residual debris and aberrant microbial populations into the colon during fasting states. When interdigestive migrating complexes are blunted due to autoimmune damage to the interstitial cells of Cajal or enteric neurons—frequently triggered by previous acute gastroenteritis via molecular mimicry involving cytolethal distending toxin B (CdtB) and vinculin—prokinetic agents become indispensable. Clinical management frequently incorporates low-dose macrolides (erythromycin) or serotonin receptor agonists (prucalopride), alongside natural prokinetics such as ginger root extract (Zingiber officinale) and Actinidia deliciosa (kiwifruit) extracts, which act on ghrelin and cholinergic receptors to reinstate propulsive peristalsis.

Concurrently, barrier fortification is paramount. Chronic luminal distension and bacterial lipopolysaccharides (LPS) induce tight junction degradation, upregulating zonulin and compromising mucosal immune defence. Nutritional protocols must therefore prioritise L-glutamine as the preferred fuel source for enterocytes, alongside short-chain fatty acid precursors that nourish colonocytes and indirectly support small intestinal repair via anti-inflammatory signalling. Dietary frameworks, including short-term low-FODMAP interventions, serve as a temporary palliative measure to starve fermentative populations, but long-term dietary restriction must be avoided to prevent starvation of beneficial commensals. The ultimate clinical objective remains the restoration of structural enzyme expression, Paneth cell antimicrobial peptide secretion, and normal ileocecal valve competence. Only through this exhaustive, physiologically congruent remediation can patients transition from chronic inflammatory dysbiosis to sustained gastrointestinal resilience.

Summary: Key Takeaways

Chronic bloating is rarely an isolated gastrointestinal annoyance; rather, as robustly catalogued in gastroenterological literature including The Lancet, it frequently servesas the primary clinical sentinel for Small Intestinal Bacterial Overgrowth (SIBO). Mechanistically, SIBO represents a profound ecological disruption wherein colonic-type microbes aberrantly colonise the proximal small intestine. Here, premature fermentation of ingested carbohydrates by hydrogen-, methane-, and hydrogen sulfide-producing taxa yields massive gas volumes that overwhelm mucosal absorptive capacity. As evidenced by landmark trials indexed on PubMed, this microbial over-proliferation degrades the brush-border disaccharidases and drives tight-junction zonulin-mediated permeability, precipitating systemic endotoxemia and chronic immune activation. For UK practitioners navigating the rising tide of functional gastrointestinal disorders, recognising SIBO as a stealth pathogen network—rather than mere irritable bowel syndrome—is paramount. True resolution requires moving past symptomatic suppression to dismantle the underlying microbial dysbiosis, restore migrating motor complex (MMC) integrity, and re-establish homeostatic barrier function across the enterocyte interface, a paradigm shift continually championed by INNERSTANDIN.