What Is SIBO?

What is SIBO?

SIBO, or small intestinal bacterial overgrowth, is defined as the presence of excessive numbers of bacteria in the small bowel causing gastrointestinal (GI) symptoms, according to the American College of Gastroenterology. There is also intestinal methanogen overgrowth (IMO) that fits under the SIBO umbrella, and we will discuss later in this article.

Listen to The Gut Show episode on this topic on iTunes or Spotify, watch the video below, or keep reading to learn more about SIBO.

 

Is it IBS, SIBO or both?

SIBO is commonly seen in those with IBS, likely more so in those with post-infectious IBS. Both IBS and SIBO share similar symptoms, including abdominal pain, bloating, and diarrhea.

Chances are, IBS increases the risk of SIBO and SIBO may be misidentified as IBS (or maybe it’s both!). There is also thought that SIBO is causing IBS-D and IBS-M types.

The reason why there is so much confusion and SIBO seems so poorly understood is that we don’t have a clear definition that’s agreed upon by all in the medical community, testing methods are highly debated, and treatment is also not fully agreed upon. This is all being researched, so there should be more on this in the coming years.


Are there any other conditions that may be linked to SIBO?

Other conditions that can be associated with SIBO include:

  • Ehlers Danlos Syndrome

  • Liver cirrhosis

  • Pancreatic insufficiency

  • Diabetes

  • Narcotic use

  • Adhesions and pseudo-obstructions

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SIBO is a state where there is an overgrowth of both aerobic and anaerobic bacteria in the small intestine. New research suggest this may be more of an imbalance of microbes versus simply an overgrowth. Usually, the small intestine has very low levels of microbes, while the large intestine is home to the majority of our important microbial community.


Types of SIBO

The type of SIBO highlights the main type of gas that’s being produced by the type of microbe(s) that is overgrown.

SIBO can be broken down into 2 main types:

  • hydrogen dominant

  • hydrogen sulfide dominant

New research is highlighting hydrogen sulfide dominant, but hydrogen is most commonly the type thought of when we say SIBO.

Hydrogen producers include the Escherichia and Klebsiella bacterial species. Hydrogen sulfide producers have yet to be fully identified at the time of this article, but we know one species is Fusobacterium. Hydrogen sulfide SIBO is most commonly associated with diarrhea.

Then there’s IMO, which is under the umbrella but not actually SIBO. The reason why is that IMO is the overgrowth of methanogens, who produce methane gas, anywhere in the intestines versus only the small intestine. IMO is most commonly associated with constipation.

What’s interesting is that both hydrogen sulfide and methane producers use hydrogen gas for fuel. So as hydrogen is produced in the small intestine, this gas will be taken up by one of the other gas producers and this would lead to the predominant symptom. Aka it’s very unlikely for both IMO and hydrogen sulfide SIBO to be present together. In addition to these specific bugs and how they impact the gut, there is likely an autoimmune component

How is SIBO/IMO diagnosed?

SIBO is most commonly diagnosed using a glucose or lactulose breath test. Breath tests may not be 100% accurate, but they are the most non-invasive option we currently have. Many studies support the glucose test, which may be more ideal for those with severe symptoms. The lactulose test may be able to detect distal SIBO, but it can lead to diarrhea, which may not be ideal.

The test used should measure all three gases (hydrogen, methane, and hydrogen sulfide) after the substrate is consumed, and over a period of time to measure gas production throughout the small bowel and the large bowel. If one or more of the gases are included in the test, results may not reflect the full picture of what’s going on. The only test on the market (to my current knowledge at the time of this article) that measures all 3 gases is the TrioSmart Breath Test. This can be ordered by a doctor.


A positive diagnosis from a breath test would be:

  • >20 ppm rise from baseline of hydrogen in the first 90 minutes in the test

  • >10 ppm rise of methane anytime in the test

  • >3ppm rise of hydrogen sulfide anytime in the test

What are the treatment options?

For SIBO, the goal is to clear the small intestine of the bacterial overgrowth, then prevent reoccurrence with building up diversity of the gut microbiome, addressing the cause (if possible), and supporting healthy gut motility. The conventional treatment method is to use antibiotic therapy to that target and clear the overgrowth.

Rifaximin is most often used for hydrogen dominant, and a combination of rifaximin and neomycin is used for methane dominant. For hydrogen sulfide, the same treatment may be used and bismuth subsalicylate may be added for increased treatment success.

Antibiotic therapy will typically last for 10-14 days, and some may need more than one round. This depends on how high the numbers are from the breath test. Other antibiotics may also be used based on insurance coverage and to avoid potential side effects from certain ones based on clinical assessment.

Alternative treatment options

The alternative treatment option is to use herbal therapy, which has still shown a lot of great success, although not as much as the conventional method. This method uses a combination berberine herbs, allicin (for methane dominant), oregano, and neem to have an antibiotic effect.

There may also be other supplements used to aid in treatment based on severity of the overgrowth and to help with treatment success. These options have not been as thoroughly studied and could also come with side effects, so it’s important to work with a knowledgeable practitioner if you are considering this option.

After clearing overgrowth, motility may be supported with prokinetic medications or supplements, in addition to diet and lifestyle medications. The goal is to keep the bowels moving and avoid constipation that may increase risk of overgrowth relapse. To build up the diversity of the microbiome, diet and stress management are both key.

Let’s talk more about diet

To start, there is no research currently available done on SIBO and diet. There is a lot of information available about how diet may be involved in SIBO, but the truth is that there isn’t science to back that up yet.

During antibiotic or herbal therapy, the consensus is to avoid complete restriction low fermentable carbohydrates (FODMAPs), to allow bacteria to flourish in order to be removed. FODMAPs may be removed in some cases for symptom management during treatment. There is no “wrong” way to do it, so this will be individualized to each person.

There are mixed reviews on the use of probiotics during treatment. A 2017 study shows a benefit to probiotic therapy, but the exact strains or types aren’t really clear. The S.boulardii strain has been looked at and may be beneficial, especially for those going through antibiotic therapy.

After treating with antibiotics or herbal therapy, following a low FODMAP diet or other low fermentable carbohydrate diet can help control symptoms as you build up diversity in the gut. There is very little research to recommend a clear nutritional approach, but practitioners agree that modifying fermentable carbohydrates is effective. The low FODMAP diet is the most common dietary approach used.

Are dietary restrictions long term?

When it comes to dietary restrictions, these should not be long term. Like IBS, we want to test for any triggers as we work to treat the underlying cause (keep reading!). If someone starts a specific protocol after treatment, this doesn’t mean they will have to be in that protocol forever.

As you finish and move away from treatment, building up a diverse microbiome is key. This is done through a diverse fiber diet and stress management. Working with a specialist dietitian, like those on the Gutivate team, during and after treatment can be vital for treatment success, decreasing symptoms after treatment, and preventing relapse.

In Gutivate’s premium 1:1 program, you get individualized care with hand-in-hand support, which means you have someone on your team to help you feel confident in your body again. If you want to learn more about how this would work for you, apply for a consult call here to see if it would be a good fit!

 

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Hi, I'm Erin, founder and lead dietitian at Gutivate. Myself and my team are here, across the US to help you get control of your IBS!
 
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