Strategies to Strengthen the Gut-Brain-Microbiota Axis in IBS

This article was inspired by our recent CEU webinar 'IBS and the Mind-Body Connection: The Role of the Gut-Brain-Axis in Digestive Health’, presented by Niki Strealy, RDN, LD. In this webinar, Niki shares her deep expertise on all this and more in depth. Click the link at the bottom of this article to access the webinar. 

The Role of Gut Microbiota

The gut microbiota include up to 40 trillion microbes and consist of not only bacteria but also fungi, archae, viruses and protozoa. Their highest concentration is in the large bowel, where roughly 70% of all microbes reside [1]. While original estimations of the ratio of microbiota to human cells was roughly 10:1, more recent literature points to a much lower ratio of about 1:3:1 [1]. The vast majority of these genes, roughly 99%, are microbial or archea, with Bacteriodes and Firmicutes in the highest abundance [2].

At birth, the gut microbiome is fully sterile. From birth onwards a host of factors influence the development of each person’s unique gut microbiota composition. Maternal factors that influence its make-up include the gut microbiota of the mother, vaginal infection, method of birth and periodontitis. During development, method of feeding (such as breast milk versus formula), childhood exposures and antibiotic use all contribute to evolution of a unique microbiota composition. By two to three years old, the adult microbiome is generally established. From there, diet and lifestyle factors play a vital role in helping to maintain a healthy Gut-Brain-Microbiota Axis [3].

Dietary and Lifestyle Changes to Modulate Symptoms of IBS

Diet is among the primary factors that influences the composition of the gut microbiota and is therefore of utmost importance when providing patients strategies to prevent and manage symptoms. 

Carbohydrates and fiber play a primary role in supporting multiple factors of digestion, including increasing microbial diversity. In particular, microbiota-accessible carbohydrates (MACs) are carbohydrates that resist digestion and are instead available for gut microbiota to ferment or metabolize into beneficial compounds, such as short chain fatty acids (SCFAs). Resistant starch, in the form of cooked and cooled pasta, rice or potatoes, as well as prebiotic fibers are excellent sources of MACs. When fermented by gut bacteria, they produce SCFAs and other metabolites, which in turn feed and strengthen the mucus layer of the gastrointestinal (GI) tract to support and regulate barrier function, metabolism and immune function [4].

Still, a diet high in prebiotics can also be high-FODMAP, which in turn may contribute to IBS symptoms. There is a wealth of evidence to support a low-FODMAP diet as a way to manage IBS symptoms like bloating, flatulence and diarrhea. This is because limiting FODMAP intake, and particularly complex FODMAP carbohydrates like oligosaccharides and galacto-oligosaccharides, reduces available substrates for fermentation by the gut microbiota and therefore also reduces gas production (a byproduct of fermentation). Read more about how to help patients find a sustainable long-term approach to ensure prebiotic intake while on a low-FODMAP diet and download our free guides to support dietary expansion here.

While it's best to add fiber through dietary modifications, supplementary fiber sources like psyllium, acacia gum and partially hydrolyzed guar gum (PHGG) can help patients meet needs when dietary intake is limited. Low-FODMAP prebiotic fibers like PHGG are often well tolerated among patients and may be a good first-line recommendation when adding a fiber supplement. 

In addition, despite mixed research, many patients seek probiotics to also modulate gut microbiota. Note that both the American Gastroenterological Association (AGA) & (American College of Gastroenterology) ACG recommend against the use of probiotics due to low quality research and the high risk for bias in many of the published studies [5,6]. Work with patients 1:1 to explore their interest in probiotics, discuss the potential benefits and consequences or costs, and educate on various types and considerations when selecting one to trial. Reliable databases to research brands, strains and applications based on IBS sub-type include the International Scientific Association for Probiotics and Prebiotics (ISAPP) and the Clinical Guide to Probiotic Products provided by AEProbio.

Beyond Diet: Lifestyle Changes to Manage IBS

A range of medications are available for IBS, though most are insufficient to adequately provide symptom relief. Pharmaceutical options include medications that target pain related to IBS, such as low dose tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs), as well as those that aim to re-establish gut microbial diversity and intestinal motility and secretions [6].

In light of the limited efficacy of pharmaceuticals for IBS, more recent focus has been on the role of behavioral therapies to manage symptoms. The enteric nervous system regulates digestion and responds to stress. Thoughts, feelings and behaviors all impact the communication between the brain and gut through millions of nerves that lie within the enteric nervous system, such as the vagus nerve, among many others.

For example, gut directed hypnotherapy (GDH), either delivered via app or in live sessions, helps patients learn automatic skills to support and strengthen communication between the gut and brain. Patients first enter a deepened hypnotic state, following which they engage in imagery focused on GI symptoms and receive suggestions focused on relaxation and normal bowel movements [7]. Research shows these interventions can have a direct effect on gut microbiota activity and metabolism. This in turn supports optimal vagus nerve function via modulation of communication between the brain and gut [8]. 

Cognitive Behavioral Therapy (CBT) also helps re-establish and strengthen communication in the Gut-Brain-Microbiota Axis by helping deactivate the sympathetic nervous system (the ‘fight or flight’ response) and activate the parasympathetic nervous system (the ‘rest and digest’ response) [7]. CBT sessions help patients gain greater awareness of the connection between thoughts, feelings and behaviors and the internal and external factors that influence their symptoms. Through app or in-person treatments, patients develop a more robust set of coping skills to self-regulate GI-related experiences, which subsequently helps with resilience and symptom management. CBT may reduce IBS symptom severity through changes in intestinal microbiota and serotonin levels, which modulate peripheral signals from the microbiota and pain processing [9].

While research is still nascent, growing attention is also being paid toward various other strategies to support gut microbiota health. These include mindfulness and mindful eating, meditation, diaphragmatic breathing and other strategies to stimulate the vagus nerve. Additional behavioral strategies widely recognized to help regulate symptoms include better sleep and sleep hygiene, which both helps reduce symptoms and can be a result of symptom relief. In addition, regular physical movement also supports intestinal motility, serotonin production and healthy gut microbiota activity [10].

Conclusion & Future Outlook

When promoting a healthy Gut-Brain-Microbiota-Axis, a plant-based diet rich in fiber is key to support a robust gut microbiota and prevent or correct potential dysbiosis. The range of non-diet tools available to manage symptoms via modulation of gut microbiota is robust and growing. Going forward, research into novel interventions such as fecal microbiota transplant (FMT), virtual reality (VR), glutamine supplementation, bile acid modification, acupuncture and much more may provide additional insight into how to support the Gut-Brain-Microbiota-Axis.