Deep Dive: Interesting Bacterial Solution for Irritable Bowel Syndrome?

Irritable bowel syndrome (IBS) is a functional disorder^[1] of the gastrointestinal system affecting approximately 5-20%^[2] of the general population. People with IBS experience abdominal discomfort and/or a change in the number of bowel movements and stool consistency in response to a variety of triggers, such as diet changes, infection, or stress. IBS is not defined by an anatomical abnormality or measurable biomarker in the human body. Rather, it is characterized^[3] by its symptoms, clinically diagnosed using the Rome IV^[4] criteria, and classified into one of four subtypes depending on which symptoms are predominant: diarrhea (IBS-D), constipation (IBS-C), mixed diarrhea and constipation (IBS-M), or undetermined/unspecified (IBS-U). These subtypes are shown in Figure 1. Additional symptoms include bloating, urgency, and flatulence. Although not life-threatening, the discomfort and embarrassment associated with IBS greatly impacts quality of life^[5], resulting in missed workdays, reduced work productivity, and social anxiety.

Figure 1: Types of IBS

The pathophysiology of IBS is not yet fully understood, and identifying the root cause for each person can be difficult. Theories range^[1] from impaired brain-gut interactions and gastric motility, to stress, dietary allergies/intolerances, intestinal infections, alterations in gut immune activation, and intestinal permeability. In the absence of a proper understanding of the underlying cause, treatment is focused primarily on relieving symptoms. Therapies include emotional and lifestyle modifications (cognitive behavioral therapy, hypnotherapy, stress management, sleep hygiene), dietary interventions (restrictive or elimination diets, high-fiber intake), and medications (laxatives, anticholinergic agents, anti-diarrheal medications, antidepressants, antibiotics). However, not everyone responds to these treatment modalities^[1], and there is no consistent “cure” for IBS, to date.

In an effort to explore alternative treatment options, research on the role of the gut microbiome in IBS is growing, and some data suggest^[6] that alterations in gut bacteria can trigger or exacerbate IBS symptoms. This idea stemmed from observations of IBS occurring after certain types of acute GI infections (post-infectious IBS). When compared to healthy controls, the microbiome of people with IBS^[7] often, but not always, shows significant differences in composition, such as a reduction in Bifidobacterium and an imbalanced Firmicutes to Bateroidetes ratio. Thus, probiotics, defined^[8] as a “live microorganism that, when administered in adequate amounts, confers a health benefit on the host,” offer promise in effectively treating IBS for some people, and several researchers have explored the effects of probiotic supplementation on the expression of IBS symptoms.

The study under review is a meta-analysis that sought to compile and evaluate all the currently available data on the efficacy and safety of probiotic use in people with IBS, focusing exclusively on randomized controlled trials (RCTs).

Irritable bowel syndrome (IBS) affects up to 20% of the general population and has a significant impact on quality of life. The cause is not yet fully understood, and current treatments are not always effective or tolerable for everyone. Studies suggest the gut microbiome plays a significant role in the manifestation and modulation of IBS, making probiotics a promising option for effective treatment. This meta-analysis of RCTs aimed to examine the efficacy and safety of probiotic use in people with IBS.