Irritable bowel syndrome (IBS) is a challenge; it is the most common reason for referral to gastroenterology clinics. Researchers in Malaysia published Microbiome and Irritable Bowel Syndrome – A Review on the Pathophysiology, Current Research and Future Therapy. The excellent overview appeared June 2019 in Frontiers in Microbiology journal.
Highlights for our purposes were the role of gut microbiota in relation to Irritable Bowel Syndrome (IBS) as well as therapy options which include prebiotics, probiotics and fecal transplantation among many others.
What is IBS?
Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by chronic, recurrent abdominal discomfort and pain, with changes in bowel habits. Four major subtypes prevail depending on the stool pattern accompanying IBS: constipation, diarrhea, mixed bowel habits and unclassified.
IBS is multifactorial in origin: Genetic and epigenetic factors, stress-related nervous and endocrine systems, immune dysregulation and the brain-gut axis all may contribute. Triggers may be foods, toxins, adverse life events, chronic infections and dysbiosis.
In addition to abdominal discomfort or pain, and stool changes, anxiety and depression are highly linked with IBS.
Gut Microbiota Alterations
Dysbiosis, a loss of microbial diversity and richness, is linked to IBS in multiple reports. For example, the composition and activities of Lactobacilli and Bifidobacteria are heavily compromised in IBS patients. A meta-analysis which was performed on 13 studies showed differences in expression in IBS patients compared to healthy controls for Lactobacillus, Bifidobacterium, and Faecalibacterium prausnitzii.
The review discusses other studies and cites common organisms as well as parasites in IBS patients.
The beneficial effects of probiotics on alleviating visceral sensitivity, intestinal permeability and inflammation further support the role of gut microbiota in IBS.
Stress also influences the gut-brain axis affecting intestinal motility and permeability, visceral sensitivity, immune responses and gut microbiota composition. Interestingly, changes in serotonin levels are observed and appear to be implicated.
Exacerbation of symptoms with ingestion of specific foods such as gluten and (a protein found in grains such as wheat, rye, spelt and barley) and FODMAPs (short-chain carbohydrates fermented by gut bacteria into gases but poorly absorbed) are common. Many trials reveal the effectiveness of FODMAPs restriction diet in improving global IBS symptoms.
Given their alterations in IBS, it is not surprising that strains of Bifidobacterium and Lactobacillus noticeably improve symptoms in IBS in studies.
Indeed, several meta-analyses of trials comparing probiotics against placebo in reducing IBS symptoms found probiotics to be superior, according to the review article.
Mode of action? Probiotics may reduce gut inflammation, strengthen barriers and help eliminate pathogens.
By fueling growth of specific bacteria, prebiotics alter the microbiota. Also of benefit are short chain fatty acids (SCFAs) produced during metabolism.
Fecal Microbiota Transplant (FMT)
Replacing dysfunctional microbes by way of fecal transplant is also promising. The authors list positive outcomes from many studies. In particular, bifidobacterium-rich donor feces showed considerable potential to increase diversity in IBS patients.
Given the messy optics of FMT, oral fecal capsules were tried and met with comparable effect in one study.
Prebiotics, probiotics and transplanting microbiota are making inroads into an insidious health care challenge, which can affect up to one in five people during their lifetimes.