Understanding SIBO (Small Intestinal Bacterial Overgrowth): a hard to treat condition

SIBO in Australia is a hard-to-diagnose condition that can potentially cause multiple intestinal problems. Modern Functional Medicine in Australia offers an alternative.

You probably heard about gut dysbiosis, and how your colon (large intestine) is affected, with overgrowth of specific bacterial species. However, the colon is not the only part of your gut affected by gut dysbiosis1-2.

The small intestine is home to relatively small numbers of microbes, compared to the colon, but it can still develop an important condition known as SIBO or Small Intestinal Bacterial Overgrowth. It is important to understand all about SIBO testing, how SIBO can affect your health, and what you can do about it. Modern Functional Medicine in Australia offers a better way to address SIBO.


The small Intestine microbiota: Basics


Our gastrointestinal tract, from the mouth to the colon, is inhabited by trillions of microbial organisms. But the microbial composition of our gut varies greatly across different parts of the gut, due to factors like genetics, mode of delivery, gestational age, diet, drug use, sleep pattern and exercise1-2.

Most notably the stomach and small intestine of healthy people contains only a relatively small number of bacteria, compared to the large intestine. The colon or large intestine hosts about 1 trillion bacterial cells per millilitre of fluid. In contrast, the small intestine holds only 10,000 bacteria per millilitre1-4. Despite this relatively low microbial abundance, the small intestine microbiota plays important roles in the body, including:

      • Being the primary place where mineral absorption takes place3. Also, vitamins like folate and Vitamin K are produced by gut bacteria found in the small intestine5-6.


      • Producing high levels of the Short-Chain Fatty Acid butyrate, mostly through the action of specific bacterial groups like Lachnospiraceae, Ruminococcaceae and Bacteroidetes7.


      • Helping our body process fats. A study using mice found that gut microbiota found in the small intestine have an essential role in the digestion and absorption of fats8.


      • Digestion of common sugars. A recent study found that fructose, a typical sugar found in fruits, is processed in the small intestine, converted in glucose and other metabolites that can be used by the body9.


The microbial diversity of the stomach and small intestine is significantly different from that of the colon, mostly due to key physiological differences between these two organs. The stomach and small intestine are characterised by peristalsis (muscle movement of food) and the presence of gastric acids, which have strong anti-microbial effects. These two factors are key drivers of the different composition and abundance of microbes between the small and large intestine.

The stomach and small intestine are characterised by bacterial groups like Lactobacillus, Staphylococcus, Streptococcus, and Bacteroides2-3, whereas in the large intestine is populated by bacteria like Escherichia coli, Bacteroides, Enterobacter and other anaerobic species (Figure 1).

SIBO Bacterium Content and Diversity in Gastrointestinal Tract

Figure 1. Typical bacterial content and diversity in the stomach and intestinal tracts of healthy people.

An important feature of the small and large intestinal microbiota is their proximity, which can sometimes cause problems, particularly in the small intestine.


What is Small Intestinal Bacterial Overgrowth (SIBO)


SIBO or Small Intestinal Bacterial Overgrowth is a complex disorder characterised by excessive growth of a few microbial species within the small intestine. Small Intestinal Bacterial Overgrowth may also occur due to changes in the diversity of bacteria commonly found in the small intestine10-12. Commonly, the bacterial overgrowth in patients with Small Intestinal Bacterial Overgrowth occurs due to microbes from the colon colonizing and overgrowing within the small intestine. Although less common, Small Intestinal Bacterial Overgrowth can also occur due to overgrowth of some bacteria commonly found in the small intestine10-12.


How can Small Intestinal Bacterial Overgrowth affect your health?


If you suffer from Small Intestinal Bacterial Overgrowth, the bacteria growing in your small intestine can cause different problems, depending on the species. Some potential health problems of Small Intestinal Bacterial Overgrowth include:

      • Excessive bacterial carbohydrate fermentation, leading to gas production11-12


      • Poor absorption of certain vitamins, through the effect of certain bacteria on bile acids11


      • The excess of bacteria can compete with our body for the consumption of macro- and micronutrients, potentially limiting our nutrient absorption12


      • Damage to the intestinal cells (villi) may occur, which can result in carbohydrate malabsorption13


      • Decreased production of important chemicals, like short-chain fatty acids13-14


      • Intestinal and system inflammation14-15


      • Increased gut permeability16


Some common symptoms associated with Small Intestinal Bacterial Overgrowth in adults and children include:


      • Abdominal pain or discomfort


      • Bloating and abdominal distention


      • Abdominal distention


      • Diarrhea


      • Indigestion


      • Constipation


      • Gas and bloating


Less common symptoms may include weight loss, malnutrition, and vitamin deficiencies. In children, Small Intestinal Bacterial Overgrowth has also been associated with stunting, a disease that affects millions of children worldwide17.


What causes Small Intestinal Bacterial Overgrowth


There is no single cause of Small Intestinal Bacterial Overgrowth, as this condition is likely multi-factorial, and co-occurring with other problems. However, there are several risk factors that have been associated with Small Intestinal Bacterial Overgrowth18. These include19,

      • Altered anatomy of the intestine – Conditions like diverticulosis or any other condition affecting the anatomy of the small intestine


      • Hypochlorhydria – changes in the level of acidity could allow for the growth of non-native bacteria in the small intestine


      • Motility dysfunction – changes in the way the small intestine functions and moves food down to the large intestine can result in bacterial growth leading to Small Intestinal Bacterial Overgrowth


      • Immune deficiencies – certain immune conditions like hypogammaglobulinemia or certain disorders of cellular immunity have been associated with Small Intestinal Bacterial Overgrowth


      • Diseases of the small intestine – conditions like IBD (ulcerative colitis and Crohn’s disease) or IBS (Irritable bowel syndrome)


      • Conditions like Gastroesophageal reflux disease (GERD), where stomach acid or bile flows into the oesophagus, affecting the acid levels in the stomach and small intestine


      • Diabetes mellitus, type I or II


      • Previous history of excessive antibiotic use


      • Dysfunction of certain organs, like liver cirrhosis, chronic pancreatitis, or renal failure


      • Previous episodes of food poisoning


Small Intestinal Bacterial Overgrowth – SIBO Testing and Modern Functional Medicine Australia


A primary difficulty with understanding the role of Intestinal Bacterial Overgrowth in your health is testing. SIBO testing remains exceedingly difficult to perform, due to the difficulties in obtaining samples from the microorganisms living in the small intestine.

Modern Functional Medicine Australia offers a different alternative for SIBO testing and treatment. At AUSCFM, we take a comprehensive approach when suspecting Small Intestinal Bacterial Overgrowth in a patient. In this sense, modern functional medicine is a step ahead, compared to the standard medical approach to SIBO in Australia. At the Australian Centre for Functional Medicine, we consider Small Intestinal Bacterial Overgrowth (SIBO) a complex condition that is likely embedded within other ailments affecting a patient. There are multiple conditions associated with Small Intestinal Bacterial Overgrowth and SIBO testing is just one of the aspects we investigate. Modern Functional Medicine Australia offers a comprehensive approach.

We employ two SIBO-specific tests:  a 3-hour long breath test and an endoscopy, where a sample of liquid from your small intestine is procured. In addition, we perform other tests, such as urine and stool tests, to get a global understanding of what other conditions may be causing your symptoms. The stool test, for example, involves a genomic analysis of the microbiota in your colon, which can give us an idea of potential problems that may affect your overall health and may even influence the health of your small intestine.

Treatment for this condition can include a diverse range of protocols, including standard medical approaches such as antibiotics and antimicrobials, or the use of prebiotics and probiotics as well as changes in lifestyle factors.

SIBO in Australia is an underdiagnosed condition, which is likely to affect many Australians. Anyone exhibiting symptoms like vomiting, constipation, diarrhoea, bloating, malnutrition, and other, be experiencing Small Intestinal Bacterial Overgrowth but is likely to go undiagnosed for this condition.




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