It seems like everywhere you look on the internet these days, someone is talking about SIBO. So what is it? How do you even pronounce it? Why should it matter to you? All are great questions that will be answered below.



SIBO (typically pronounced ‘see-boh’) stands for Small Intestinal Bacterial Overgrowth and put simply, it’s an accumulation of bacteria in the small intestine. You might be thinking, 'but, aren’t we supposed to have bacteria in our digestive systems’?

Yes, definitely! But bacteria are normally found in their trillions lower down in the large intestine (or colon), with the small intestine having much fewer. When bacteria from the large intestine moves up into the small intestine and overgrows, SIBO occurs. In most patients, SIBO is not caused by a single type of bacteria, but is an overgrowth of the various types of bacteria that should normally be found in the colon.



Ok, so what difference does it make that you’ve ended up with too much bacteria in your small intestine? There are many reasons, but the most obvious ones are the symptoms.



·         Bloating and/or excessive gas (usually soon after eating)

·         Abdominal pain or discomfort

·         Either diarrhoea or constipation (or alternating between the two)

·         Excessive burping and acid reflux/GORD (will also occur soon after meals)



·         Food sensitivities

·         Joint pain

·         Skin rashes

·         Iron and B12 deficiency

·         Respiratory symptoms such as asthma



You might be thinking this sounds just like IBS? — gas/bloating, diarrhea/constipation, abdominal cramping. Well it turns out that up to 80% of IBS cases could actually be caused by SIBO. The great news is that there may be an underlying cause for IBS that can actually be addressed!

The bacterial overgrowth in the small intestine of SIBO causes hydrogen, methane and/or hydrogen sulphide gas production. These gases cause the symptoms of IBS but they also can cause damage to the small intestinal wall. The surface of the small intestine is like a shaggy carpet, with finger-like protrusions called villi. On these villi are microvilli, which normally secrete enzymes to break down food, so nutrients can be absorbed. When the surface of the small intestine is damaged as in SIBO, absorption of nutrients from food is reduced.


SIBO can therefore result in:

·         Malabsorption of monosaccharides (carbohydrates) and amino acids (proteins)

·         Fermentation of disaccharides by bacteria causing hydrogen, methane and hydrogen sulphate gasses

·         These gasses themselves are damaging to the gut wall

·         Malabsorption of vitamins (especially B12 and Folic acid)

·         Malabsorption of minerals (especially, magnesium, iron, and calcium)

·         A damaged small intestine wall causing 'leaky gut' allowing larger food particles to pass through, leading to an immune response in the body



SIBO is actually pretty complicated and therefore often there can be more than one contributing factor. Our digestive system moves food along in the one direction, through your small intestine to your large intestine. If this is disturbed for various reasons (see below), it allows bacteria to travel backwards up the digestive tract.

Post infectious: a case of gastroenteritis can often start the development of SIBO. It can cause damage to your Migrating Motor Complex (MMC). The MMC is a cleansing wave that sweeps through your small intestine every 90 minutes to sweep stray bacteria out. It’s the grumbling, and growling sounds your stomach makes between meals. The MMC can also be impaired as a result of inflammatory bowel disease; ie, Crohn’s disease and Ulcerative Colitis.

Medications: acid blocking drugs: such as proton pump inhibitors and antacids for stomach acid reflux, lead to low stomach acid (hypochlorhydria). Stomach acid is one of the ways your body controls pathogens in the digestive tract and ensures bacteria from the colon can’t move into your small intestine. Recurrent use of antibiotics and some medications such as Morphine and other opiates can also affect the bacteria in your intestines, leading to SIBO.

Lack of pancreatic enzymes: is often linked to low stomach acid. The release of acidic contents from the stomach valve (pyloric sphincter) into the upper part of the small intestine triggers the pancreas to release digestive enzymes. If the contents of your stomach aren’t acidic enough the pancreas doesn’t get the signal it needs to release these enzymes.

Chronic stress, ageing and H. pylori infection can also decrease stomach acid output. Stress can also causes changes in the speed with which food moves through your gastrointestinal tract (motility/peristalsis). If motility of the small intestine slows down or works improperly, pooling and stagnation can allow for bacterial overgrowth and fermentation to occur. This can occur in type 2 diabetes, post radiation complications and hypothyroidism. Restoring proper motility in the small intestines is a major focus of eliminating SIBO for good.

Altered anatomy: structural changes of the digestive tract such as scarring and adhesions (from C-sections, laparoscopy, appendectomy, gastric bypass or gallbladder removal) can alter the normal anatomy of the small intestines and impact the movement of food through the gut. 



The most non-invasive option which also has strong clinical relevance is a breath test using lactulose and/or glucose. This simple test can be done in a clinic or at home. It measures the levels of hydrogen and methane gas in your breath over a couple of hours, as these are the by-products of the bad bacteria in the small intestine. This test can be arranged for you and a treatment plan to eradicate the bacteria and relieve your symptoms will occur as part of your treatment plan. 

A stool test (or CDSA), while useful for other aspects of digestive health is not diagnostic for SIBO.



SIBO has many potential causes, so treatment plans need to be individualised and address not only the symptoms but also the underlying cause.

The medical approach may include diet modification, antibiotic treatment, and the use of medicines to promote motility.



·         Temporary diet changes to reduce symptoms and support healing. Foods to restrict are typically ‘FODMAPS' foods (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, all of which are particular types of carbohydrate). It is important to note that any restriction of foods should be short term only. Many of the foods that exacerbate SIBO symptoms (FODMAPS foods) are important for feeding the beneficial colonic bacteria and for ongoing health.

·         Use of antimicrobial and antifungal herbs to reduce bacteria in the small intestine and deal with any overgrowth of disease-causing bacteria. 

·         Improving the health of the gastrointestinal tract to reduce inflammation, support appropriate secretion of stomach acid and digestive enzymes and restore motility.

·         Support a diversity of beneficial bacteria in the colon. Suitable strains of probiotics maybe recommended.

·         Support of any underlying condition contributing to SIBO.



SIBO can be tricky to treat however depending on the underlying cause and individual factors, as a minimum, treatment would take at least three months.

If you think you may have SIBO, or you’ve already been diagnosed, I can help guide you through the process. You can contact me for more information, or book in for a consultation.

Jen Kellett