was successfully added to your cart.

We have previously discussed the causes of small intestine bacterial overgrowth and the testing options available. In this article, we look at the effects of small intestine bacterial overgrowth. We will discuss macronutrient (protein, fats, carbohydrates) malnutrition, micronutrient (vitamins and minerals) malabsorption, weight loss, gall stones and irritable bowel syndrome.

Macronutrient Malabsorption

Weight loss resulting from SIBO has been described. Malabsorption to all three macronutrients – fat, protein and carbohydrate – may lead to reduced availability of nutrients to the host and subsequent weight loss.

Fats – Steatorrhoea (fat malabsorption) may result from SIBO and is principally due to bacterial deconjugation of bile acids. In addition, free bile acids are toxic to the intestinal mucosa, resulting in gut inflammation and malabsorption (Grace et al., 2013).

Proteins – It has been postulated that in SIBO, the gut bacteria are responsible for breaking down dietary protein in the gastrointestinal tract. As a consequence, there is a diversion of dietary nitrogen into urea formation, with the result that it becomes unavailable for protein anabolism by the human host, resulting in protein malabsorption (Grace et al., 2013).

Carbohydrate – Carbohydrate malabsorption can result from SIBO due to reduced disaccharidase function (enzymes that break down certain types of sugars called disaccharides into simpler sugars) and increased carbohydrate degradation by bacteria.  This macronutrient malabsorption coupled with chronic gut symptoms, which often include bloating, cramps and diarrhoea, may result in reduced dietary intake and subsequent weight loss (Grace et al., 2013).

Due to this last point, it is not surprising then that many people with IBS/SIBO benefit from a low carbohydrate diet. In one study of 2,390 patients (Goebel-Stengel et al., 2014) with unexplained gastrointestinal symptoms, roughly one third were symptomatic lactose malabsorbers and two thirds symptomatic fructose malabsorbers, respectively. One quarter of patients had a combined symptomatic carbohydrate malabsorption.

Micronutrient MalabsorptionIncreased consumption of vitamin B12 by bacteria, and therefore its decreased bioavailability produces symptoms similar to those presented by patients with malignant anaemia. Patients with normal intestinal enteric flora rely on gastric intrinsic factor to bind to vitamin B12 to permit absorption. It has been shown that people with bacterial overgrowth absorb significantly less vitamin B12 compared to controls, and this was reversed with antibiotic therapy.

Folate levels can be normal but frequently are elevated due to increased synthesis of folate by small bowel bacteria (Dukowitcz, 2007).

Due to impaired fat absorption a deficiency of most fat-soluble vitamins – vitamins A, E, and D – is also common (Grace et al., 2013).

Irritable Bowel Symptoms

Studies suggests that anywhere bbetween 4-72% of people with irritable bowel syndrome have SIBO. Bacteria are involved in fermentation of disaccharides (certain sugars including sucrose, lactose, and maltose), which results in the generation of gases (hydrogen, carbon hydroxide, hydrogen sulfide, methane) responsible for bloating, abdominal pain and/or constipation, while fermentation of short-chain fatty acids causes osmotic water movement to the intestinal lumen, and then diarrhoea (Grace et al., 2013).

Watch this 3 minute video for a great explanation: click here.

Many Other Conditions

As discussed in our introductory article on SIBO, SIBO has been associated with many chronic conditions such as chronic fatigue syndrome, arthritis, hypothyroidism and coeliac disease.

It is also important to bare in mind that it may be that SIBO is a consequence of a disease state. For example it may be that a dysregulated immune system has caused an overgrowth of bacteria in the small intestine, or that hypothyroidism has causes slow gut motility that has caused a bacterial overgrowth. However a bacterial overgrowth may then perpetuate the initial condition (compromised immune function or hypothyroidism in this example).

In either case, eradicating the bacterial overgrowth may still be a key component of the overall programme. The only way to know is to treat the SIBO and see, as detailed in a paper by Goshal (2011):

If the symptoms disappear, it is likely that SIBO rather than the underlying disease is responsible for the symptoms

Gall Stones & SIBO

Gallstone disease (GSD) is one of the most prevalent abdominal diseases. Heaton et al. reported that one particular factor associated with GSs is the slow intestinal transit time. In their study, they found that the mean transit time was significantly longer in women with GSs than in controls. Even after cholecystectomy 15–20% patients have persistence of vague dyspeptic symptoms. Change in small intestinal motility and SIBO may cause this problem. A study showed that OCTT was significantly higher in gallstone patients as compared to controls which might be the reason of SIBO in gallstone patients. OCTT was further increased after cholecystectomy which may be the reason of post cholecystectomy symptoms in these patients.

Small Intestine Bacterial Overgrowth: Effects – Conclusion

The effects of SIBO clearly can manifest in a broad range of symptoms and conditions. The high co-morbidity between chronic fatigue syndrome and small intestine bacterial overgrowth suggest this is a condition that should often be considered when working with a patient.