Understanding IBS and the link to the microbiome


If you frequently experience digestive discomfort after eating a meal, then you are not alone. It is thought that one in five people regularly experience abdominal symptoms and altered bowel movements after eating (1).

  • The most common symptoms of IBS include:-
  • abdominal pain and discomfort
  • the sensation of needing to empty your bowels urgently
  • feeling or looking bloated around your stomach
  • diarrhoea, constipation or a combination of the two
  • excessive gas causing flatulence

You may experience any or all of these symptoms, and they should always be discussed with a GP, who will be able to carry out testing to rule out other underlying conditions with similar symptoms.

What is the underlying cause of IBS?

IBS is a syndrome, defined as a collection of similar symptoms rather than a specific disease. It is not known what causes IBS, but it is likely to be a variety of different factors. The severity of symptoms ranges from mild to extreme and have usually been persistent for more than 6 months prior to receiving a diagnosis (2). Research into the cause of IBS has covered the following areas:-

  • post-infectious IBS with sudden on-set after a bacterial infection in the gut
  • long term or frequent usage of certain antibiotics
  • gut/brain connection and over sensitivity to sensations of digestion
  • anxiety and stress
  • abnormal movement of food through the gut (too slow or too quick)
  • other dietary and lifestyle factors
  • microbiome (role of bacteria, virus and fungi living in out guts)

The role of the microbiome

A relatively new area for research in IBS has focused on the complex role of the microbiome, which populate our intestines. For some people with IBS a low level of diversity in the bacteria residing in their gut has been found to be a common occurrence, enabling more virulent strains to take over. It is unknown if this profile of bacteria colonisation is a cause or consequence of IBS (3).

The role of the immune system

A recent study into post infectious origins of the disease found evidence of an immune reaction causing inflammation at a localised area of the intestines, where the previous infection had taken place. Antigens, which are the allergenic proteins found in common allergens such as milk, eggs and wheat present in the gut at the time of infection were remembered by the immune system after the infection had cleared, causing an immune response upon later consumption. An immune cell known as a mast cell releases histamine in response to the antigen, causing an inflammatory response. In this scenario, anti-histamines were found to alleviate symptoms (6).

What treatment is there for IBS?

For some people, eliminating common trigger foods such as alcohol, caffeine, wheat, spicy or fatty foods may help. It is not always easy to remember everything you have eaten over the course of a few days, so keeping a food dairy for a couple of weeks may help establish dietary patterns and make it easier to correlate these with symptoms. Not drinking enough liquid, or a diet low in fibre may contribute to bowel pain and bloating due to constipation. Sharing this information with your doctor or health professional is a useful step to eliminating potential causes.

FODMAP testing

If dietary assessment does not bring about positive yield results, then a FODMAP test may help. FODMAPS (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) are a group of short-chain carbohydrates, which when poorly digested in the small intestine attract water, and on entry to the large intestine ferment causing gas and discomfort. Food sources of these short-chain carbohydrates include garlic, onions, lactose from dairy products such as milk, honey, wheat, rye and some sweeteners. The diet works to establish which of the FODMAP containing foods may need to be reduced or eliminated from the diet and the rest can usually be re-introduced successfully (7). This should always be done in conjunction with a FODMAP trained health professional such as a dietician, as excluding food groups can lead to deficiencies.


Prebiotics are a type of fibre which are the preferred food source for the bacteria in our guts associated with positive health benefits. Treatment with prebiotics has been found to decrease symptoms in 58% of people suffering from IBS (8). Prebiotic fibre occurs naturally in many foods such as garlic, onions, bananas and legumes and increasing overall fibre intake has many beneficial health benefits, with most people not currently meeting the minimum recommended daily amount of 30g for adults (9). Increasing fibre intake should be done very gradually to avoid a worsening of symptoms and with the support of a nutritionist or dietician.


Probiotics are live micro-organisms found in cultured and fermented foods such as aged cheese, yoghurt and pickles such as kimchi and sauerkraut. It is thought that by consuming probiotics you can change the diversity of the microbiome, increasing the quantities of beneficial bacteria. Probiotics have been widely studied in conjunction with IBS with variable results (8). At the moment there are no recommendations in regards to specific strains to treat IBS, but it is an exciting area for future research.

Managing Stress and Anxiety

Due to the complex interactions between the gut and the mind, learning how to manage stressful situations and deal with anxiety in a positive way may also help with decreasing symptoms (10) (11). The following methods may be worth considering as part of a holistic approach to managing your IBS:

  • Yoga
  • Meditation
  • Cognitive Behavioural Therapy
  • Hypnotherapy

In summary, although there is a lot of exciting research taking place, there is currently no one treatment that has been found to work effectively for everyone suffering with IBS. Working with a qualified health professional will help you to tailor a treatment plan that supports your individual needs. Before changing any aspect of your diet, you should always consult with a registered health professional such as a nutritionist, dietician or your GP.

Author BIO

This article has been written by Thrive Panel Nutritionist Helen Morris, a Registered Associate Nutritionist at rndnutrition.co.uk a food and nutrition consultancy specialising in gut health.


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