The link between your gut microbiome and IBD

Feb 22, 2021

What is inflammatory bowel disease?

IBD is a chronic, inflammatory, auto-immune condition of the gastrointestinal (GI) tract. There are two major clinical forms, ulcerative colitis (UC) and crohn’s disease (CD). Whereas in UC, the inflammation and ulceration is contained to the large bowel (colon and rectum), in CD, the entire digestive system can be affected, from the mouth to the anus. However, both involve periods of relapse and remission and it is estimated that around 70% of those with CD and 25% of those with UC will need surgery during their lifetime.

The global prevalence of IBD is increasing and over the last decade has become a public health challenge. Developed countries have the highest prevalence, however, more recently, the incidence has increased in developing countries such as Brazil, China and South Korea. IBD imposes a large burden on patients and affects their quality of life by often impacting their ability to work and to socialise. The exact aetiology is unknown but an altered gut microbiota is considered to be a key factor. However, it is unclear whether alterations are the cause or consequence of intestinal inflammation.

What is the gut microbiome?

The gut microbiota is diverse, consisting of bacteria, fungi and viruses, with over 1000 different species of bacteria. In a healthy gut there are four main families: Bacteroides, Firmicutes, Actinobacteria and Proteobacteria. Diversity of species is crucial in order to maintain balance and ensure harmony in our gut. Every time we eat, the microbes work to help us break down our food and extract the nutrients we need. Importantly, what we eat is also food for our microbes and each thrive on a different food group. That means that if we eliminate a food group, the microbes that feed on that particular group will die out. When there is a loss of harmony in our gut, dysbiosis occurs and this results in a higher proportion of inflammatory microbes emerging. As our gut houses 70% of our immune system, this can increase our risk of immune impairment and associated illnesses, including IBD.

The type of dysbiosis most commonly associated with IBD is a decrease in bacteria diversity, especially Firmicutes and Bacteroides, and an increase in species belonging to the Endobacteriaceae family. These bacteria invade the gut mucosal lining, causing bloody diarrhoea and ulceration of the colon. However, although many studies have recognised the dysbiosis which occurs in IBD, the causal role has not been established and the microbiome composition has varied across patients studied. This may be due to a number of factors, including the disease state of the subjects, specimen type and location and materials, and methods used for analysis. It is therefore unclear whether there is a specific bacterial species/strain, or multiple species/strains which might cause or only exacerbate IBD.

70 perfect of the immune system lives in the gut. This makes it easier to understand why a healthy gut microbiome can strengthen our immune system. However, as a healthy gut environment enables our immune system to function optimally and IBD is an autoimmune condition, it makes sense to do everything we can to ensure that our gut microbiota is as diverse as we can make it. The single most important way we can do this is to change our diets and eat more fibre.

Read part 2 of this blog to find out about the importance of fibre and how to include it in your diet, even when you have digestive disorders. This is not always easy to do and advice from a healthcare professional can really help. Do book with our team to find out how to transition healthily to a plant based diet.


Bulsiewicz, W (2020). Fiber Fueled. Penguin Random House: USA

Crohn’s & Colitis UK (

Khan. I, Ullah, N et al (2019). Alterations of gut microbiota in inflammatory bowel disease (IBD): Cause or consequence? IBD treatment targeting the gut microbiome. Pathogens 8(3):126

Ni.J, Shen. T.C, Chen. E, Z et al (2015). A role for bacterial urease in gut dysbiosis and Crohn’s disease. Science Translational Medicine. 9(416)

Images source: Canva

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