SIBO – Small Intestinal Bacterial Overgrowth

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What is it?

While the large intestines have trillions of bacterias in them, the small intestines have relatively few. SIBO is as the name implies: the small intestines have an overgrowth of bacteria when they shouldn’t, especially ones that aren’t typically found there. These bacteria eat the food you eat and produce excess gas as a byproduct. 

Types of SIBO

• hydrogen-dominant SIBO (when you have an overproduction of hydrogen gas)
• methane-dominant SIBO (also known as intestinal methanogen overgrowth or IMO because it’s not actually bacteria producing the methane but rather a similar type of organism called archaea.
• hydrogen sulfide-dominant SIBO (also known as Intestinal Sulfide Overproduction or ISO)

SIBO, IMO, and ISO are now often recognized as 3 different conditions (vs types of SIBO) with different testing, associated symptoms, and treatment.

People can have 1 of these conditions or multiple ones at the same time.

What causes SIBO?

Contributing factors to SIBO can be

• impaired intestinal motility*
• structural changes in the intestines which allow pockets of bacteria to multiply*
• chronic stress
• inflammation
• bowel surgery
• and more

*Endometriosis adhesions is one of multiple factors that can cause this.

For some of us, SIBO can be a co-condition of endometriosis and contribute to our abdominal bloating (the beloved endobelly), digestive problems, (pain, diarrhea, gas, constipation, nausea) or non-digestive problems (fatigue, vitamin deficiencies, histamine intolerance.)

What type of doctor can help?

With SIBO, it’s important to work with a qualified doctor who has experience with SIBO. This could be a local gastrointestinal doctor, in which case hopefully the consults, testing, and/or treatment would be covered by insurance. Some people also see naturopaths or functional medicine doctors. There is often a lack of evidenced-based medicine with naturopaths and functional medicine doctors, so make sure to research before choosing one of those doctors should you go down that path.

Testing for it

The most common way to diagnose SIBO is typically through a breath test which measures levels of different gases produced in the gut such as hydrogen, methane, and hydrogen sulfide. With SIBO, IMO, or ISO, there is an overproduction of the corresponding gas.

There are multiple breath tests, such as lactulose or glucose based. You drink the substance, the bacterias in your gut eat the sugar, and then you test the gas released over a certain period of time, typically a few hours. Some SIBO tests only test for hydrogen and methane and not for hydrogen sulfide, potentially missing people who have ISO. And unfortunately, these tests are not always reliable and can be falsely negative at times, which means that you could still actually have SIBO even if the test shows as negative. Because of this, some doctors will treat based on symptoms, even if the test is negative.

In my own individual case, because of this and the fact that I had symptoms associated with SIBO as well as many of the common contributing factors that may lead to it, my doctor didn’t do any SIBO testing on me and instead we did a treat-and-see approach. When the first round of treatment reduced my symptoms, she gave me a working diagnosis of SIBO and we did several rounds of treatment until my symptoms were significantly reduced.

A few years later, I did the TRIO SMART breath test for SIBO, which tests for all 3 gases, and tested positive for Methane dominant SIBO (also known as intestinal methanogen overgrowth).

There is also a more invasive method for testing, which is the small intestinal aspirate in which they remove a fluid sample from your small intestines and test it for SIBO.

Treatment

Generally, there are 3 treatments for SIBO: antibiotics, antimicrobials, or an elemental diet.

Some doctors may do medications and dietary changes, such as putting the patient on a low FODMAP diet or low-fermentation diet. What each patient needs is individual. Note: it’s not recommended to follow a low FODMAP diet for more than a few months. Cutting out FODMAPs long term can hurt gut health, so goals for using the diet should also include reintroducing a variety of foods after a period of time.

While each treatment type has been shown to reduce SIBO, they have different pros and cons, costs, accessibility, etc. Some doctors find antimicrobials to be a helpful first-line treatment, because these can also address gut dysbiosis in the colon as well.

Unfortunately, SIBO may need multiple rounds of treatment, as it can often recur in patients.

The first time I treated SIBO (under the suspected diagnosis from a naturopath) I used antimicrobials for 2 weeks. After 3 rounds of this, my symptoms diminished significantly. I treated SIBO again a few years later after testing positive for IMO on the TRIO SMART test. My GI put me on Rifaximin and neomycin for 2 weeks, which are common antibiotics for IMO.