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Can probiotics help with inflammatory bowel disease?

A older meta-analysis surprisingly found that probiotics do not have a clear effect on IBD. Since then, new research has come to light.

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Study under review: Systematic review with metaanalysis: the efficacy of probiotics in inflammatory bowel disease.

Introduction

Inflammatory bowel disease (IBD) is a collective term that includes both Crohn’s disease (CD) and ulcerative colitis (UC). The differences between these two types of IBD can be seen in Figure 1. IBD affects as many as 450 people out of every 100,000[1] in the United States. While the cause of IBD and its rising numbers is still unclear, it is thought to be due to complex interactions[2] between genetic[3], immune[4], and environmental[5] factors. Recent evidence also suggests that the gut microbiome[6] may be of particular importance.

Typical changes in the gut microbiota seen in IBD[7] include an increase in the abundance of bacterial species associated with increased inflammation, a decrease in bacterial species linked to reduced inflammation, and a decrease in the diversity of bacteria. Differences have also been found[8] between the bacteria found in inflamed and noninflamed parts of the gut in people with IBD. The use of antibiotics, which can disrupt[9] the normal bacteria in the gut, has been associated with an increased risk of developing CD[10]. These separate lines of evidence seem to point gut bacteria playing a role in IBD.

Given this possible role, it’s plausible that the disease could be mitigated with probiotics. Probiotics are live microorganisms, usually either bacteria or yeasts, that can provide health benefits when taken in large enough amounts. In laboratory studies using a mouse model of IBD[11], probiotics have been shown to produce anti-inflammatory effects and improve the integrity of the gut wall, which suggests potential for the treatment for IBD in humans. However, the results of clinical trials using probiotics to treat IBD have so far been mixed, with some studies showing a benefit[12][13] and others reporting no effect[14][15]. This may be the result of different bacterial species or strains in the probiotics used, other differences in the way the studies were carried out, or random chance.

Several meta-analyses[16][17] have now attempted to pool[18] the evidence from all the published clinical trials examining the benefit of probiotics on people with IBD. However, there were issues with many of these. Some have combined data from studies using probiotics and synbiotics[17], which are a combination of probiotic bacteria and prebiotic fiber, making it harder to separate out the effects of probiotics alone. Others used data from both children and adults[16], which makes it hard to see the effects in children or adults on their own. Furthermore, recent research examining the quality of meta-analyses that have investigated the effects of probiotics in IBD found that many have been of relatively low quality[19], and that better quality meta-analyses were required.

The study under review is a systematic review and meta-analysis of RCTs investigating the benefit of probiotics in different subgroups of people with IBD. Where possible, the authors sought to identify the effect of individual probiotic preparations in inducing remission in active Crohn’s disease and ulcerative colitis. They also examined the ability of probiotics to maintain remission for participants with inactive disease, and prevent relapse of CD after surgery carried out to treat the disease.

Inflammatory bowel disease (IBD), an umbrella term which includes both Crohn’s disease (CD) and ulcerative colitis (UC), is an increasingly common disease associated with changes in the microbiota and immune system of the gut. With their ability to modulate the intestinal microbiome and downstream effects on the immune system, probiotics have the potential to benefit patients with IBD. However, the results of pertinent randomized controlled trials (RCTs) have been mixed. The study at hand is a systematic review and meta-analysis of all the currently available RCTs assessing the effectiveness of probiotics in adult patients with IBD.

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