Could SIBO be the cause of your symptoms?

Small Intestinal Bacterial Overgrowth (SIBO) occurs when there is an excessive number of bacteria in the small bowel, causing unwanted gastrointestinal symptoms such as severe bloating and lots of gas! SIBO can be often overlooked as the symptoms are very similar to IBS symptoms but there are a few key differences.

Normally the lower pH of the stomach and good gut motility ensure gut microbes do not grow in the small bowel and remain in the large bowel (colon) where they should be. However if our food travels more slowly through the gut or the pH of our stomach changes (due to medication) this creates an ideal breeding ground for gut microbes in the small bowel. These bacteria have a party feeding off the food passing through the gut and cause a heap of unwanted symptoms. When our gut microbes are feeding they produce methane and hydrogen gases which can cause symptoms including severe abdominal bloating (bloating being the most common symptom), abdominal pain, excessive gas production and often smelly flatulence, nausea/vomiting and diarrhoea or constipation. Whilst SIBO symptoms mimic those of IBS I find those suffering with SIBO report more severe symptoms. Clients also regularly describe feeling full very quickly during a meal and additionally (as if that isn’t a lengthy list of symptoms already) some have diarrhoea with fat malabsorption which can result in foul smelling, greasy pale stools that are difficult to flush.

Nutrition concerns

Nutrient deficiencies can be common in SIBO including low levels of vitamins including Vitamin D, iron and B vitamins due to a number of factors including poor absorption of nutrients, bacterial consumption of nutrients such as protein and B12 or production of vitamins and/or poor nutrient intake. It is common for clients to avoid eating to reduce the risk of symptoms and naturally over time this can impair their nutritional status and potentially lead to weight loss.


Consequently  when supporting someone with SIBO dietary guidance is key to help lessen symptoms and improve quality of life; but also to increase a person’s oral intake and optimise their nutritional status.

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Causes of SIBO

Small intestinal bacterial overgrowth (SIBO) can be caused by:

  • Motility disorders of digestive tract such as Irritable bowel syndrome, Gastroparesis
  • Weakened immune system
  • Untreated coeliac disease
  • Auto immune conditions such as Hypothyroidism and Diabetes
  • Low stomach acid levels due to medication or H Pylori infection
  • High alcohol intake
  • Surgery affecting digestive tract such as removal of part of intestines, weight loss surgery
  • Chronic pancreatitis
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How do I know if I have SIBO or IBS?

The symptoms of SIBO and IBS can be similar and it is not uncommon for people to have both conditions. The main difference is that IBS is a functional disorder and diagnosed when other causes have been ruled out whereas bacterial overgrowth in SIBO can be clinically determined and treated. Common tests include:


Small Bowel Aspiration and Culture

The small bowel aspiration and culture is considered the gold standard for the diagnosis of SIBO, however this is invasive and expensive and within my clinical practice I have not seen this used to date within my cohort of clients.


Hydrogen breath testing

Breath testing is an indirect method of determining if there are excessive amounts of bacteria in the small bowel. Clients are asked to drink a liquid containing a sugar that is fermented by bacteria in the small intestines. When the bacteria feed on this carbohydrate they produce gases such as hydrogen and methane which we as humans do not create. These gases then travel to our lungs where they are expelled. The breath is then analysed for levels of hydrogen and methane and a rapid rise in levels of methane or hydrogen could suggest there is bacterial overgrowth in the small intestine. Whilst this method is simple there are limitations to as intestinal transit time is individual and false positives and negative results can occur in breath testing.

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SIBO is often a consequence of another condition and therefore treatment will involve treating the bacterial overgrowth, managing the symptoms through diet and then addressing the underlying cause.



The first line treatment for bacterial overgrown in SIBO is antibiotic use, typically for 2 weeks to eradicate bacterial overgrowth in the small intestine and the most common antibiotic used is Rifaximin, as well as Ciprofloxacin and Metronidazole. It not uncommon for people to need more than one course of antibiotics and recurrence rate can be high for some people.



There is limited research on the role of diet in SIBO treatment and currently there are no evidence based dietary recommendations for SIBO treatment or prevention. Commonly, clients are fearful of eating, are limiting their range of foods or simply avoiding meals in an attempt to reduce their symptoms.  Working with a dietitian who has experience in SIBO is key to achieving a nutritionally balanced diet, increasing confidence in food choices, and correcting any nutritional deficiencies whilst also managing gut symptoms.


A low FODMAP diet may be recommended following antibiotic treatment.  Whilst avoiding FODMAPs does not cure SIBO a low fodmap diet can reduce symptoms and help to prevent reoccurrence. One way in which a low fodmap diet can help is by reducing fermentable carbohydrates in the diet to essentially “starve” the bad gut bacteria which can help manage the gastrointestinal symptoms of SIBO such as bloating and excessive gas production.


You might read about other diet therapies including a gluten free diet, The Specific Carbohydrate diet and Elemental Diet; and to date these are not recommended by healthcare professionals either due to insufficient evidence to support their role in SIBO or due to the restrictive nature of such diets.


What about prebiotics? Currently we don’t have enough evidence that prebiotics help in SIBO treatment. The American Journal of Gastroenterology Guidelines 2020, advised to avoid certain prebiotics such as inulin, as these are fermentable fibres (high FODMAP) which feed your gut microbes contributing to increased gas production and bloating.


Further Testing


Additional testing might be required to identify the underlying cause if it is not already known e.g. motility agents if constipation is the underlying cause.


• Whilst taking antibiotics for your SIBO try to start to introduce foods back into the diet, including fodmap foods such as an apple, mango, a slice or two of bread, garlic in cooking etc in an attempt to encourage bacteria so eradication therapy is in theory more effective.

• After antibiotic therapy and with the support of a fodmap trained dietitian consider following the low FODMAP diet to address residual symptoms.

Chew food thoroughly to aid digestion as digestive enzymes present in saliva start the digestive process. Additionally by chewing food well and eating slowly you reduce ingestion of excessive air.

• What physical activity do you do? Can you minimise sedentary behaviour (the amount of time sitting down)? Moderate exercise such as walking stimulates gut motility which can help support a regular bowel movement and reduce bloating.

• If you struggle with constipation work with your GP or dietitian to help achieve a successful bowel evacuation as excess stool in the colon may reduce small intestinal motility, which may increase risk of SIBO. Learn more about how to combat constipation by clicking here.

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Next steps


SIBO is a common condition with a wide range of symptoms which might present as IBS or other gut conditions. If you feel you have symptoms of SIBO I would encourage you to speak with your doctor to get a diagnosis.

Additionally if you suspect you could have SIBO or if you are suffering from gut symptoms and need help, drop me a message by clicking this link and we can arrange a free discovery call.

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