Thinking Nutrition

Small intestinal bacterial overgrowth (SIBO): symptoms, causes and treatment

November 16, 2021 Dr Tim Crowe Episode 87
Thinking Nutrition
Small intestinal bacterial overgrowth (SIBO): symptoms, causes and treatment
Show Notes Transcript

Small intestinal bacterial overgrowth (SIBO) is a condition where there is an abnormal increase in the number of bacteria in the small intestine – especially types of bacteria not normally found in this part of the digestive tract. Most of the focus on gut health is given to the population of bacteria in our large intestine, so in this podcast, I’ll look at the consequences of what happens when bacterial growth gets out of control in our small intestine.

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Small intestinal bacterial overgrowth (SIBO) is a condition where there is an abnormal increase in the number of bacteria in the small intestine – especially types of bacteria not normally found in this part of the digestive tract. Most of the focus on gut health is given to the population of bacteria in our large intestine, so in this podcast, I’ll look at the consequences of what happens when bacterial growth gets out of control in our small intestine.

Small intestinal bacterial overgrowth, or SIBO for short, is a painful condition of the gut caused by the presence of excessive numbers of bacteria in the small intestine. If you can think back to your high school biology classes, then you’d know that the small intestine is where most of the digestion and absorption of food and nutrients happens.

Compare that to the colon which is part of the large intestine and hosts a huge population of bacteria. It’s what we normally are referring to when we talk about gut health and gut bacteria. In contrast. the small intestine is normally very sparsely populated by bacteria – it has about 100-fold fewer bacteria in it compared to the colon. But that can change. Bacterial overgrowth can happen when bacteria translocate from the large intestine up into the small intestine or it can also happen naturally when bacteria in the small intestine grow out of control.

SIBO has been shown to negatively affect both the structure and function of the small intestine and can significantly interfere with digestion and absorption of nutrients, primarily by damaging the cells lining the intestines.

 There are plenty of potential culprits for causing SIBO. Factors that increase your risk of developing SIBO include:

  • Having low levels of stomach acid as seen with Helicobacter pylori infection or as is commonly seen with ageing. The reason is that an acidic environment can help keep bacterial growth in check.
  • Also, using medications that reduce stomach acid production including proton pump inhibitors will also increase the risk of SIBO
  • Then there are conditions resulting in reduced gastrointestinal motility such as gastroparesis (which delays stomach emptying), irritable bowel syndrome, Crohn’s disease, coeliac disease, Parkinson’s disease and small bowel dysmotility
  • It can also be seen as a complication of gastric bypass surgery
  • And people with a suppressed immune system and people with diabetes causing neuropathy are also at risk.

 So what are the consequences of this? Signs and symptoms of SIBO are non-specific and are similar to other digestive disorders such as IBS, lactose intolerance and fructose malabsorption so it is not something you can immediately diagnose just based on a symptom checklist. More on diagnosis shortly. Common symptoms of SIBO include abdominal pain and discomfort, bloating, indigestion, diarrhoea, constipation, excessive gas and flatulence and unintentional weight loss. Severe complications include malabsorption, malnutrition and nutrient deficiencies.

 How can you be tested for SIBO?

Because of the large amount of symptom overlap of SIBO with other gastrointestinal conditions like IBS, it is important that proper testing is done to ensure a correct diagnosis and treatment. The most definitive way to determine whether someone has SIBO is to examine microbes from the small intestine. Since that requires an invasive procedure by endoscopy, the most practical way to diagnose SIBO is with a lactulose or glucose breath test. The test involves drinking a solution of either glucose or lactulose which are both types of sugars. Bacteria in the small bowel ferment these sugars and produce hydrogen and methane gas. When levels of those gases are above normal, chances are good you have SIBO. Although widely available, breath testing is less specific than other types of tests for diagnosing bacterial overgrowth, but the less-invasive nature of it makes it more feasible.

Is there a cure for SIBO?

So how is SIBO treated? The most common first-line antibiotic to address the bacterial overgrowth directly is the prescription of the antibiotic rifaximin. The problem with antibiotics though is that they are not always initially effective with many people needing retreatment up to 5 times. This raises the very serious concern of developing bacterial antibiotic resistance.

 Herbal treatments such as oil of oregano, lemon balm, and red thyme oil may present an effective alternative treatment for SIBO. A 2014 study which I’ll link to in the show notes found that herbal treatments were just as effective as the antibiotic rifaximin in treating SIBO. And from the same study, herbal treatments were just as effective as triple antibiotic therapy in people that did not respond to rifaximin. https://pubmed.ncbi.nlm.nih.gov/24891990

Dietary changes are also an important part of managing SIBO. Because bacteria feed on carbohydrates, then a diet that aims to reduce these can help. This is where a low FODMAP diet is sometimes recommended to treat SIBO. FODMAPs are short-chain carbohydrates such as lactose, fructose, fructans (which are long chains of fructose molecules) and sugar alcohols that are commonly present in dairy products, grains, legumes and certain fruits and vegetables. The reduction in fermentable carbohydrates in the diet helps to starve excess bacteria of their important food source. It is no surprise that a low-FODMAP diet is also effective at treating IBS.

An elemental diet is another option sometimes considered for people with SIBO. The diet involves taking on nutrients in an easy-to-digest form – usually a liquid mixture of amino acids, fats, sugar, vitamins and minerals. The easier and quicker digestion and absorption of nutrients mean there is less available for bacteria to feed off. And the small amount of research done so far seems positive, with a 2-week study of people with SIBO-related IBS trialling an elemental diet finding that 80 percent returned a normal lactulose breath test after 1 month. And I’ll link to this study in the show notes. https://pubmed.ncbi.nlm.nih.gov/14992438

And there is some preliminary research too showing that probiotics could have a role to play in treating SIBO because of their barrier enhancing, antibacterial, immune-modulating and anti-inflammatory effects. Here, it seems the several bacteria belonging to the Lactobacillus genus could have some benefit.

So, let’s wrap all this up. Many people who have SIBO don’t realise their symptoms are caused by bacterial overgrowth. While there can be an overlap between SIBO and many symptoms of IBS, left untreated, SIBO can lead to serious complications including nutrient deficiencies and malnutrition. With SIBO, different dietary changes work for different people, but any dietary changes should be part of specialised advice and targeted testing, usually by a breath test, to ensure a correct diagnosis, not a random tick-a-box symptom checklist you come across on the Internet.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.