To understand IBS, we need to understand the gut

IBS is a common condition affecting up to 15% of the world’s population. That’s over a billion people. With such large numbers, you would think there would be a solution in place, yet it remains unresolved. According to conventional medicine, it’s a lifelong condition and there is little hope for sufferers and no cure.


However, nutritional therapists and functional medicine love the gut, and we can tell you that there is hope. Working on the gut often forms the very foundation of a nutritional programme, after all, up to 80% of your immune system is located here, so it’s of vital importance to the body.

IBS can take many years to develop, in my case, 20 years after a bout of dysentery and giardia in India and this is a very common picture. Often triggered by food poisoning or traveller’s diarrhoea, it’s the classic chronic condition and can take years to evolve. Left alone, it can stealthily take over and diminish your health.

Understanding the gut

Our gastrointestinal tract begins at the mouth. From here, it goes into the gullet, a 2cm wide oesophageal tube, which takes it from the throat down into the right-hand side of the stomach. The body is intelligent; the connection positioned this way gives it flexibility. Can you imagine the reflux every time you moved if it fixed into the top of the stomach!

It then connects to the small intestine, all seven metres of it, and meanders around and around, in no particular order. This gives the small intestine a large surface area lined with villi and microvilli, think of them as little fingers, which work hard to break down the food we eat and pass all those nutrients into the bloodstream.

As it joins the colon, it becomes the large intestine, home to the gut microbiome, where bacteria fill this bulging tube and wait for the remnants of our food. Here, it takes time to slowly break down and absorb the indigestible leftovers from the small intestine, which can take up to 16 hours.

The colon circumnavigates the small intestine, like a picture frame, finding its exit at the anus. There are a few other organs too, such as the appendix, the liver, gallbladder and the pancreas, which play a part. All of this is the gut, so imagine there is a lot that can go wrong and it’s very complex.

So let’s break it down.

1. The gut microbiome

The gut microbiome is a melting pot of 100 trillion microbes in the large intestine. That’s a lot when you consider a human body contains only 30 trillion cells. It has important functions: to provide us with energy, to break down toxins, to spot enemy microbes, train our immune system, and the manufacture of important vitamins and minerals such as calcium, B12, folate and vitamin K.

Whilst we are unaware of the vital work being done inside us in these microbial factories, a skewed balance of these microbes can have quite an impact, such as, obesity, depression, digestive or skin issues. It’s an exciting area of growing scientific research but already we do know that our guts play host to over 1000 different microbial species plus viruses, yeasts and fungi.

2. Small intestinal bacterial overgrowth (SIBO)

SIBO accounts for approximately 60% of IBS cases. Whilst we are happy to have a thriving community of microbes in our gut microbiome, we do not want these in the small intestine.

Every day our body organises a sweep of bacteria from the small to the large intestine by a flushing mechanism called the ‘migrating motor complex’. When this doesn’t happen, problems ensue and there can be several underlying reasons for this failure, such as food poisoning, low levels of stomach acid or adhesions in the gastrointestinal tract.

As the small intestine is higher in the food chain, so to speak, bacteria here intercept and ferment more food than they should causing uncomfortable symptoms such as gas, bloating, cramping, diarrhoea and anxiety.

3. Food intolerances

The most common food intolerances you might encounter which can inflame your gut are lactose and fructose. Lactose is a type of sugar found in milk and dairy products and fructose is the sugar found in fruits, honey and many processed foods.

These become digested in the small intestine and if not absorbed by the body, are fermented by the bacteria causing bloating, gas, nausea, constipation, even headaches and brain fog. They can also contribute to leaky gut, which is permeability of the gut lining, allowing the unwanted passage of proteins and pathogens to the bloodstream.

You may be wondering why I haven’t mentioned gluten, as isn’t this the main culprit according to the press? Well, gluten is a protein that when excluded from the diet, by many IBS sufferers, is found to improve symptoms. However, wheat contains gluten and fructans, a type of carbohydrate, and many IBS sufferers can tolerate sourdough bread, made with a fermentation process, which degrades the fructans, making them easier to digest. So could this be the big problem? Research is ongoing.

4. Yeast overgrowth

When the gut microbiome becomes unbalanced, opportunistic yeast can take over. High sugar diets can feed a yeast overgrowth and if the infection persists long term then symptoms can extend to fatigue, bad breath, sugar cravings, joint pain and recurring thrush infections.

5. The gut-brain axis

You may have heard the gut referred to as the second brain. This is because there is a bi-directional communication channel via the central nervous system, between something called the Enteric Nervous System (ENS), which lines the intestines, and the brain. There is also the vagus nerve, which allows the gut to speak with the brain and vice versa. This is why they call it the gut-brain axis.

We know that stress can exacerbate IBS and trigger symptoms such as bloating, constipation, pain and cramping. Likewise, IBS symptoms can cause anxiety and sleep disturbance. It’s easy to see then how persistent stress or distress will impact our gut located immune system.

Finding the root cause

If we can categorise IBS according to symptoms, then how can we verify the root cause? A registered nutritionist will analyse your medical history, diet, and symptoms in detail and have a good indication of your IBS type. They will subsequently, be able to propose suitable functional testing to uncover where the problem lies. This is most commonly in the form of a comprehensive stool test or a breath test, which are unfortunately not available on the NHS.

Armed with this valuable information, a nutritionist can put together a wellness plan to target the underlying condition and this will consist of diet and nutrition, supplements or herbal formulas and lifestyle recommendations.
Whilst GPs or Google may recommend following a low FODMAP diet for IBS, it is not advised to follow restrictive diets long term as these can seriously deplete the beneficial bacteria, cut out important nutrients and disrupt the gut microbiome. For this reason, it is recommended to work with the guidance of a registered nutritionist if considering a FODMAPS or other restrictive diet plans.

Nutritionist Resource is not responsible for the articles published by members. The views expressed are those of the member who wrote the article.

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London E2 & NW1
Written by Michele Scarr, BA Hons CNM Dip Nut mBANT mCNHC mANP GNC
London E2 & NW1

Michele Scarr is a Registered Nutritionist and Lecturer at the College of Naturopathic Medicine. She specialises in gastrointestinal complaints, women's health, weight management and pre-diabetes.

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