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SIBO – Small Intestine Bacterial Overgrowth

IBS and SIBO Clinics  >  Digestive Conditions  >  SIBO – Small Intestine Bacterial Overgrowth

What is SIBO 

SIBO – Small Intestine Bacterial Overgrowth is an accumulation of too much bacteria in the small intestine.  The overgrowth of bacteria can be good or bad bacteria but there is quite simply just too much of it. The excess bacteria often interferes with digestion, having an impact on the way you can break down and digest carbohydrates – when this doesn’t work properly it often leads to bloating. Fats are often not ab sorbed properly – leaving a fatty stool and possible lower levels of the fat soluble vitamins A, D, E and K. And up to 50% of people with SIBO have intestinal permeability also known as leaky gut. 

The main symptoms of SIBO are the same as the symptoms of IBS (Irritable Bowel Syndrome) and according to a study published in the American Journal of Gastroenterology, SIBO can be present in up to 84% of cases of IBS and is therefore considered by world SIBO experts to be the underlying cause of IBS. In two thirds of people SIBO is chronic and can re occur so getting to the root cause or driver of the SIBO is as important as finding out you have SIBO and following a successful plan to address it.

What are the symptoms of SIBO

  • Diarrhoea – Usually associated with hydrogen dominant SIBO
  • Constipation – usually associated with methane dominant SIBO
  • Alternating constipation and diarrhoea
  • Gas
  • Flatulence
  • Belching
  • Severe Bloating
  • Abdominal pain and cramps
  • Leaky gut – Intestinal permeability – affecting up to 50% of people with SIBO
  • Malabsorption which can lead to Steatorrhea (Fatty Stool) or anaemia
  • Chronic pancreatitis
  • Lactose intolerance
  • Fructose intolerance
  • Sucrose intolerance
  • Iron and B12 deficiency
  • Fatigue
  • Nausea
  • Acid Reflux
  • Gerd (Gastro oesophageal reflux disease)
  • Acne rosacea
  • Skin rashes
  • Restless legs
  • Joint pain
  • Weight loss or gain
  • Food sensitivities
  • Incontinence
  • Headache
  • Interstitial cystitis
  • Rheumatoid arthritis
  • Chronic Fatigue syndrome
  • Fibromyalgia – SIBO affects 77% of people with fibromyalgia 

The different types of SIBO

  1. Hydrogen dominant SIBO – Usually associated with diarrhoea
  2. Methane dominant SIBO – Usually associated with constipation
  3. Mixed type SIBO – usually a combination or diarrhoea and constipation
  4. Hydrogen sulphide SIBO – more commonly associated with constipation and often accompanied by joint and muscle aches.


Your own individual health picture or jigsaw puzzle.

Over the past 10 + years I’ve seen thousands of people with IBS and SIBO and each person has had their own individual set of symptoms and probable causes. No two people are ever exactly the same. This is one of the reasons the NHS finds it so difficult to deal with IBS and SIBO. I always talk in terms of a person’s individual health picture which is made up of different sized pieces and although the majority of people with IBS will share quite a few of the same pieces the size of those pieces and therefore the relevance to that individual is always different.

What are the possible contributory factors or causes of SIBO

The world of SIBO is picking up speed and we know that there can be multiple reasons why an individual may have SIBO. Unfortunately for two thirds of people SIBO is chronic and will re occur. This makes it super important that the drivers and possible cause of the SIBO are investigated and dealt with as well as the SIBO or it may come back.

In some cases, just one of the drivers – or causative factors are present and for others there can be multiple drivers or factors that lead someone to be diagnosed with SIBO. Everyone that has SIBO will have their own unique set of factors, drivers and triggers. Here at IBS and SIBO clinics we work on building a health picture for each individual where we consider all of the possible contributory factors that may have led you to get a diagnosis of SIBO. In some cases this is relatively straightforward for us and sometimes it can be a little like restoring a picture in a museum – as we address one imbalance or trigger another one becomes clear and that needs to be worked on as well. It may sound complicated but we are well practised in building your individual health picture and peeling back the layers to address any and all contributory factors.

Possible contributory factors

Food poisoning and the migrating motor complex

The MMC -migrating motor complex is responsible for making the cleansing sweeping like motion that switches on in between meals to clean the small intestines. This cleaning wave should move undigested food and excess bacteria towards the large intestines.  When the MMC is faulty undigested food isn’t swept away and becomes food for the bacteria causing or exacerbating SIBO. The major cause of malfunctioning MMC is food poisoning. The study below is associated with C. Diff but other forms of food poisoning bugs are known to also cause issues with the MMC and SIBO.

Thyroid problems

Simply put your Thyroid is responsible for the ‘speed’ at which your metabolism and many of the bodies functions go – if you have low thyroid function then as a general rule all system of the body work more slowly and this includes digestion and motility – constipation is one of the symptoms of low thyroid function and the slowing of the movement of the contents of the intestines can impact on bacteria levels and SIBO.

Scar tissue or abdominal adhesions

If you think of the digestive process a little like a stream or river – it should flow freely and anything impacting on this flow can cause or contribute to SIBO. Scar tissue from abdominal operations such as appendectomy removal of the appendix and adhesions caused by Inflammatory bowel disease and non-digestive abdominal issues such as include female health issues including caesarean sections or endometriosis can all impact on SIBO.

Low stomach acid – hypochlorhydria

Low levels of stomach acid are known to impact negatively on bacterial overgrowth. One of the jobs of stomach acid is to switch on hormones that tell the body to move the food mix along for the next stage of digestion. The acidity also helps to switch on the production of pancreatic enzymes and bile flow both of which are important for breaking down and digesting out food.

Drug-induced hypoacidity (Low stomach acid)

Proton pump inhibitors also known as PPI’s such as omeprazole or Lansoprazole are the leading cause of drug induced low stomach acidity. The NHS discuss on their webpage how PPI’s are over prescribed. They also discuss the associated risk of an increase of fractures in post menopausal women but it is also known that PPI use impacts on and can cause SIBO too.

Pancreatitis / Chronic pancreatic insufficiency

The study below shows that there is a correlation between pancreatitis and SIBO. And the second study mentions how SIBO should be considered when pancreatic insufficiency is present.

Inflammatory bowel disease

People with inflammatory bowel disease are known to have reduced motility which may or may not be due to adhesions either of which can impact on SIBO., 2011, Clinical Predictors

Ileocecal valve

The ileocecal valve is like a gate way between the small and the large intestines – It should keep the contents of each area separately. It can be stuck open or stuck shut and may not open and close properly and in some cases it can be removed all of which impact on SIBO.

Celiac disease

Celiac disease is a disease where the immune system reacts so strongly to gluten that is found in wheat, barley and other gluten containing grains that the villi. – small finger like projections in the small intestines where we absorb our nutrients are damaged and thicken meaning we can no longer absorb our nutrients efficiently. Studies are available that show there can be a link between Celiac disease and SIBO.

Other motility issues

Most of the contributory factors above impact by slowing the digestive flow. There are many other conditions and diseases that can impact on th

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is such as; scleroderma, autonomic neuropathy in diabetes mellitus, post-radiation enteropathy, small intestinal pseudo-obstruction and blind loop syndrome