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Recent studies show distinct microbiota differences between those affected by IBS and those who aren't.1,4,5 In addition, dysbiosis, an imbalance of the microbiome, can be identified in 73% of IBS patients, compared to 16% in healthy individuals.1 Additionally, perturbed microbial metabolism has been shown to result in a greater production of hydrogen gas, indoles, phenols, and other compounds in those affected by IBS. These findings pave the way to identifying specific IBS biomarkers1 that could enable more rapid, accurate diagnosis.

Likewise, determining the role of gut dysbiosis in IBS pathophysiology and symptom severity points towards potential management options. Reestablishing microbiome health could improve both the GI symptoms and the psychological comorbidities associated with IBS.5 Here we take a deeper exploration into the microbiome and the potential for life-changing management for IBS patients.


IBS's A common concern and a major healthcare burden
IBS is a prevalent condition, particularly in developed countries where it is thought to affect at least 10 to 20% of the population.3,6,7 Its onset is insidious, primarily affecting those under the age of 50 (after which the incidence drops by 25%), and it has a prevalence that is 67% higher in women compared with men.2,8,9 In addition to the serious impact IBS has on the lives of patients, IBS also represents a major burden on healthcare services and society, particularly because current treatments can only help with symptom management. The healthcare cost in the U.S. alone exceeds $20 billion each year,10 and the direct and indirect healthcare costs are comparable to other chronic diseases such as hypertension, asthma, and migraine.3


The need for new IBS management options
With the exact causes of IBS unknown, the condition is characterized and diagnosed by its symptoms: abdominal discomfort/pain, relief upon defecation, changes in stool pattern, altered bowel habits (diarrhea, constipation), bloating, dyspepsia, dysphagia, nausea, and pain.1,10,11 It is often associated with other somatic comorbidities, mental health conditions (including depression and anxiety) and visceral hypersensitivity.1,2,11

A variety of environmental factors are known to influence IBS, including stress, environmental toxins, nutrient depletion in our foods, food hypersensitivity, poor water quality, chronic infections, antibiotic usage, increased use of antibacterial products, and dysbiotic gut microbiota.1,11–17 As a chronic condition with symptoms that can come and go over periods of days, weeks, or months, IBS can seriously impact quality of life.18 In the absence of a cure, the first step in symptom management involves lifestyle and dietary modifications- most commonly, the adoption of low fermentable oligo-, di-, and monosaccharides, and polyols (FODMAPs) and gluten-free diets, plus regular exercise and psychological therapy.5,10 Pharmacological interventions are used to target some specific symptoms of IBS; however, some of these medications may themselves result in serious adverse events.19


The role of the microbiome in human health
Humans are home to trillions of microbes-bacteria, archaea, viruses, fungi, and multicellular parasites20-which play an important role in many of the physiological and pathophysiological processes that influence host health. Each of us has about 20,000 human genes in our 23 chromosome pairs. But, amazingly, researchers have discovered that our microbial genetic catalog ranges from 2 to 20 million microbial genes. So, at the genetic level, we are, at best, 1% human and 99% microbial. From this perspective, the genes of our microbiome essentially present a second genome which augments the activity of our own.21,22

An increasing amount of research demonstrates the importance of the microbiome in maintaining gut health, with these microbial communities playing a vital role in gastrointestinal homeodynamic balance.23 The human gut is highly dynamic and undergoes temporal changes from birth to adulthood. In the first years of life, the microbiota grows and diversifies. It then stabilizes in adolescence, and, in adulthood, the composition often changes once more, becoming less diverse. Research suggests that the human gut is likely to be affected by environmental factors, including xenobiotics, stress, diet, and lifestyle. Furthermore, the gut microbiome itself is also likely to be a good predictor for metabolic variables and clinical phenotypes.


How does the microbiome offer solutions for IBS management?
Many studies have concluded that dysbiosis of the gut microbiota plays an important role in the pathogenesis of IBS,5,6 and the Rome Foundation recently incorporated this view into its clinical guideline about the manipulation of the gut microbiota in IBS.24 Distinct differences have been observed between the intestinal microbiota of IBS patients compared with healthy controls. In the latter, intestinal bacteria typically comprise Firmicutes (64%), Bacteroidetes (23%), Proteobacteria (8%), and Actinobacteria (3%).1 However, in IBS patients, results have consistently shown increased amounts of Firmicutes and reduced amounts of Bacteroides.6 In addition, it has been observed that the different subtypes of IBS have different gut microbiota composition-for example, a lower abundance of butyrate-producing bacteria in IBS-D and IBS-M.1,6

Further studies have explored the bidirectional pathways of the gut-brain-microbiota axis, establishing that signals from the brain can influence the sensory, motor, and secretory functions of the GI tract.6 Conversely, dysbiosis of the gut microbiota can activate mucosal immunity, leading to a damaging of the epithelial layer, which functions as a protective barrier, and resulting in dysmotility and hypersensitivity in IBS patients.6 Furthermore, with the intestinal barrier function also linked to brain and neurologic function, disruption to that barrier can also influence all the other body systems, including the central nervous system.16

It therefore makes sense that modulating the microbiome to reduce dysbiosis should offer a clinical benefit to IBS patients. Studies show that probiotics combined with beneficial microorganisms already present in the GI tract, through several mechanisms, contribute to healthy gut balance and immune function-for example, by preventing pathogens from increasing intestinal permeability by improving mucosal barrier function.25,26 Probiotics directly support both the innate and adaptive immune responses by beneficially modulating the inflammatory response and positively influencing the function of our immune cells-not only helping to educate the immune system during development but also maintaining healthy immune function throughout life. Likewise, prebiotics selectively stimulate the growth and/or activity of beneficial gut bacteria, promoting the production of short-chain fatty acids (SCFAs) that help regulate gut mucosal immune responses.27

In addition, as the microbiome influences neurotransmitter synthesis (for example, the serotonin produced by the gut microbiota) and the brain-gut axis, these insights may help provide new treatments for gut-brain disorders like IBS.16


Case studies of microbiome modulation for IBS management
Some recent case studies have explored the benefits of microbiome modulation for IBS management. For example, one study investigated the impact of a medical food with a unique blend of probiotics and prebiotics on IBS symptoms.28 The study found that patients who received the medical food had significant improvements in their IBS symptoms compared with the placebo group. The combination of probiotics and prebiotics in the medical food was shown to enhance gut microbiome diversity and reduce dysbiosis, leading to improved clinical outcomes.

Another study assessed the efficacy of a probiotic supplement in IBS patients.29 The findings indicated that the probiotic was effective in reducing abdominal pain, bloating, and overall IBS symptoms. The study highlighted the potential of probiotics as a valuable adjunct therapy for IBS management, particularly in patients with a dysbiotic microbiome.


Conclusion
Modulating the gut microbiome through probiotics, prebiotics, or medical foods holds great promise for improving IBS management. The emerging research underscores the potential benefits of restoring a balanced microbiome to alleviate symptoms and enhance overall quality of life for IBS patients. As our understanding of the microbiome continues to evolve, future studies will likely provide further insights into optimizing microbiome-based interventions for IBS.