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SIBO: Small Intestinal Bacterial Overgrowth & The FODMAP Diet

Updated: May 4

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What is SIBO?

SIBO - or Small Intestinal Bacterial Overgrowth - is when gut bacteria that normally grows in the large intestine, moves up and proliferates in the small intestine. This causes food to break down much earlier on in its journey through the digestive tract. Similar to Irritable Bowel Syndrome (IBS), this causes painful symptoms such as cramping, bloating, gas and diarrhoea.

In fact, 50% of IBS suffers also have SIBO.

What causes SIBO?

Similar to IBS, it is often caused by dysbiosis in the gut microbiome, aggravated after antibiotics, food poisoning or a travel bug, causing gut inflammation.

Symptoms are similar to IBS

This includes constipation, diarrhoea, severe bloating, possible cramping, gas, foul-smelling stools, sometimes blood in stools or sudden urgency to use the bathroom.

In addition, because the bad bacteria are active higher up the gut, acid reflux, nausea, bad breath and increased difficulty digesting fats are also experienced.

Testing for SIBO

A GP can diagnose SIBO using two methods; firstly assessing symptoms provided by the patient and feeling the abdomen for excess gas, and secondly via a breath test that measures the amount of hydrogen and methane present. The hydrogen and methane are byproducts of the bad bacteria (gas).

Alleviating with The FODMAP Diet

It is a restrictive eating programme designed to reduce the symptoms by starving the bad gut flora of the food it loves, called fermentable carbohydrates, whilst restoring nutrition to the patient. In fact FODMAP is an acronym of these types of carbohydrates:







By starving the bad bacteria, it provides an opportunity to work on gut repair using herbal antimicrobials and supplements, whilst also repopulating the good gut bacteria with pre and probiotic foods.

By restoring the balance the the small intestine, symptoms should ease, and through careful monitoring, prohibited foods can slowly be reintroduced. This will identify if there's a particular carbohydrate type causing problems.

In addition to eliminating FODMAP foods, it is suggested to cut out other foods and beverages that often cause nausea and reflux: caffeine, alcohol, fizzy and soft drinks and fatty and oily foods. This will also aid in improving overall gut health.

If you think you may have SIBO, why not reach out for a free consultation where we can discuss your symptoms together.


Kelly Mulhall

Registered Nutritional Therapist


kelly mulhall sibo specialist nutritionist

Kelly is a Registered Nutritional Therapist who focuses on positive physical and mental wellbeing, achieved through diet, lifestyle, sleep and exercise. Having struggled for years with IBS and hormonal imbalance, and increasingly frustrated with the lack of support and helpful advice from her GP, Kelly began her own journey of healing the body from the inside out. After seeing huge improvements she quit her job to study nutrition and focus on harnessing the healing powers of food to help other people in similar situations.

I am not attempting to prevent, treat or cure any physical, mental or emotional issues. Do not disregard medical advice or delay seeking medical advice because of information you have read on this website. Do not start or stop taking any medications without speaking to your primary health care provider.


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