Small intestinal bacterial overgrowth (SIBO) is a common condition I see in my practice. If you’re unfamiliar with SIBO then please read the previous article I wrote on the topic first. Today’s article will explore SIBO testing and what you need to know before testing.
To review briefly, SIBO can cause digestive symptoms like gas, bloating, nausea, diarrhea and constipation. It is a larger than normal amount of bacteria in the small intestine. It most commonly affects the end of the small intestine, known as the ileum, but can occur anywhere along the digestive tract. Clinically, SIBO is defined by a bacterial count of greater than 10^5 in any part of the small intestine.
Who Should Get Tested For SIBO?
I will order SIBO testing if patients come to me with the symptoms I mentioned above.
There are several scenarios in which I will test someone for SIBO. The first scenario is the patient that comes to me and has seemingly had every test under the sun done. They are frustrated and don’t have answers. Maybe you can relate?
These patients have undergone ultrasound, colonoscopy, endoscopy, even CT scans. Still no answers. Often SIBO testing falls by the wayside in conventional medicine. An after thought, or completely dismissed altogether, despite a rapidly growing body of evidence on the topic. This is often one of the first things I do in these patients. I run the test.
Why? Because it’s treatable. With medications. With herbs and diet. And sometimes treatment can make all the difference in the world.
Next, I often consider testing when someone has made dietary changes and has seen either little or partial benefit from something like a Low-FODMAPs diet. Also, if they have to remain on a restricted diet in order to control their symptoms longterm then I may test them for SIBO. Most people DO respond well to a diet low in FODMAPs and it can help a lot of people. But those aren’t usually the patients that end up in my office.
Another scenario I’ll consider testing for SIBO is someone who has not felt well six months or a year after developing traveller’s diarrhea, food poisoning or a bad stomach flu. This is a strong risk for developing SIBO.
However, not everyone with digestive symptoms should have SIBO testing done. Let me repeat that: not everyone should be tested… right away anyway.
When is SIBO Testing Not a Priority?
If you have chronic diarrhea, abdominal pain and have not had any formal testing done, don’t start with SIBO testing.
The symptoms of SIBO overlap with irritable bowel syndrome (IBS), but so do many other conditions. Testing for common conditions like celiac disease, inflammatory bowel disease, and even ruling out GI bleeding and bowel cancer should be done first. Book an appointment with your GP or see a naturopathic doctor to start this investigation.
If that’s all been done you’ve likely already been diagnosed with IBS…
Is it really IBS though? Maybe…maybe not.
SIBO Test Controversies
Studies have reported on the rates of SIBO in people diagnosed with IBS. The numbers are all over the place. From as low as 10% to as high as 84% of IBS patients actually have SIBO. It makes it hard to estimate the real relationship between these two overlapping conditions.
This is the first problem. We don’t actually know how often this is happening in patients with “IBS”. It’s likely overestimated and the average number lies between 20-30% of patients with IBS-like symptoms. Further, in my clinic, about 1 in 4 patients who I suspect have SIBO, will actually test positive for it.
As I mentioned before, some docs don’t believe in SIBO as a real clinical entity. Yet, a simple search in any research databases like PubMed will reveal numerous studies linking SIBO to IBS symptoms, Crohn’s disease, fatty liver and even diabetes. Are these firm conclusions though? Not yet, and we need to do a lot more research on the topic before we truly start to understand it.
Watch Out For The Trap
“This is it… this is definitely what I have”.
“This explains everything. This is why I feel like I do.”
It’s perfectly reasonable to have these thoughts after being diagnosed with SIBO or any other condition for that matter. To put a face to a name, so to speak. Here’s the thing: you may have SIBO and it may be the cause of your issues. Further, successful treatment may improve most, if not all of your symptoms.
But it might not.
It may be a symptom of a larger disturbance, simply happening as a result of a poor digestive environment. Heck, treating your SIBO may have little to no impact on your digestive symptoms at all… I’ve seen it happen. And if it does, it means that SIBO is NOT the cause of your digestive symptoms it is simply happening in the background. This is important to keep in mind throughout the healing process.
But getting back to the issue on hand…
The second problem is that we can’t agree on what test is best.
The gold standard is considered a jejunal aspirate and culture. This is done during an endoscopy as the scope gathers samples of bacteria throughout parts of your small intestine. If they don’t sample where the SIBO is active then it’s not going to capture it.
When studies looked at this testing method it had the lowest rates of SIBO diagnosis at around 2-20% in patients who had symptoms consistent with IBS. It’s also fairly invasive as someone is sticking a probe down your throat. In my experience, it’s not commonly performed anyway. For these reasons it’s not all that practical for most people with digestive symptoms consistent with SIBO.
Enter the breath testing option.
SIBO Breath Testing
How does doing a breath test give us any information on whats going on in our small bowels?!
Contrary to popular belief, gas clearance from the intestines has more than two ways out. There is another way for gases to escape the body and it’s through the lungs. When bacteria produce gas, it can absorb into the bloodstream, travel to the lungs and be exhaled in the breath. Two of the gases we can reliably measure in the breath are hydrogen and methane.
What does this have to do with our gut?
Well, the only way our body produces hydrogen and methane gases is through the bacterial fermentation of carbohydrates. So the only way these end up in our breath is because there are more bacteria growing in our small intestine then there should be. This is the basis for using breath testing.
Breath testing is thus a timed test which can last up to 3 hours. It involves consuming a particular sugar and measuring the corresponding rise in hydrogen and methane gases in the breath. Did you know it only takes 90-120 minutes for food to reach your large intestine after you consume it? For this reason tests last either 120 or 180 minutes. After 3 hours, most food will have reached the large intestine, which under normal circumstances will ferment anything that remains. Therefore, we will see a predictable spike in gases measured around the 180-minute mark to indicate the test sugar has reached the large intestine. At this point, we are no longer assessing for SIBO.
A positive SIBO breath test is when you have a rise of 20 parts per million (ppm) or greater of hydrogen gas compared to baseline within the first 90 minutes of testing OR a rise of 10 ppm or greater of methane compared to baseline within the same time frame.
There are currently two types of SIBO breath tests: one using glucose (sugar) and one using lactulose (a sugar-like molecule). Each test measures both hydrogen and methane.
How does SIBO testing work?
When we ingest these carbohydrates they are rapidly consumed by bacteria. Not a problem if you have normal levels of bacteria. But when you have high amounts, which is the case in SIBO, you get lots of gas production. This causes the bowels to stretch, often activating pain receptors. This is one of the mechanisms responsible for many of the symptoms of both IBS and SIBO.
Generally speaking, hydrogen gas has a stimulatory or laxative-like effect on the bowels. For this reason, hydrogen-positive SIBO patients will often have diarrhea. On the contrary, high levels of methane can have the opposite effect, causing mild to severe constipation. This isn’t always the case and there are several different patterns that may emerge from high levels of both hydrogen and methane gases.
Now that you know a bit more about the different gases involved, let’s discuss the two test sugars involved.
Glucose Breath Testing (GBT)
Glucose or sugar is absorbed rapidly in the small intestine.
This makes sense if you think about it. Sugar balance is tightly controlled and is essential for each cell in our body to sustain life. It wouldn’t make sense if it took us 2-3 hours to access it after consuming it. Because of this, the glucose breath test is really only measuring the gas production of the bacteria in the “proximal” or nearest part of the small intestine.
If patients come in with mostly upper digestive complaints like functional dyspepsia that I think SIBO may be contributing to then I’ll use a GBT.
Lactulose Breath Testing (LBT)
Lactulose on the other hand, does a much better job at assessing the bacteria down to the “distal” or furthest section of your small intestine. The downfall of using lactulose is that it is a mild laxative. This can cause two issues. The first and more obvious one is it can worsen someones diarrhea – not what you signed up for I’m sure. The second is that it may speed up the time it takes for the sugar to reach your large intestine. This could “trick” the test into thinking you have SIBO when really, gases are supposed to rise substantially in the large intestine. Some of the studies that reported much higher rates of SIBO may have suffered from this error.
I’ll use LBT testing for most patients as it has the best assessment of the small intestine. It’s also much more suitable for those with diabetes who it may not be appropriate to consume a large amount of sugar in one sitting!
Because these tests rely on your baseline gas production being as low as possible, it’s very important to following the test prep instructions to the letter!
This is what we’ll talk about in the next section.
How To Prepare For Your SIBO Test
First of all, before you commit to doing the SIBO Test, you should know a few things.
It’s time intensive. This is where I get the biggest push back from patients.
The test takes 3 hours to complete. And while you can complete this test in the comfort of your own home, you still need the better part of a morning or afternoon to do it. Pick a day when you don’t have much on the schedule, if such a day exists for you.
Second, you are required to follow a prep diet the day before the test. This is a simple diet restricting any and all fermentable carbohydrates or high-fiber foods. This means no fruits, nuts, vegetables, or seeds. No breads and no lactose-containing foods. You can eat meats and poultry, eggs, white rice and bone broths (without bouillon or vegetable broth) during the prep phase. The purpose of the prep diet is to reduce baseline gases to zero. In addition to this, you have to do a fast for 12 hours before test collection in the morning or afternoon. I suggest you do the fasting while you’re sleeping – it’s my favourite method of fasting…
Sample Collection Schedule:
- Friday 10 AM: begin prep diet 24 hours before you plan on testing (eg. Saturday 10am)
- Friday 10PM: Fast for 12 hours over night
- Saturday 10AM: Collect first sample. Immediately consume test sugar after this first collection. Set a timer for 20 minutes
- Saturday 10:20AM: Collect second sample. repeat collection every 20 minutes until all breath samples have been collected
If this is a 3-hour test you should have ten test tubes completed.
There are also instructions regarding when you can perform the test if you were/are on medications like antibiotics or antacids. For the purpose of the test it’s best to wait at least 2 weeks after your last dose of antibiotics before collection as antibiotics reduce bacterial counts. It’s also best if antacids aren’t consumed within 4 days of testing. Please note if you have severe acid reflux or rely heavily on your medication to function, please don’t stop taking your medications. Always discuss this with your doctor first.
Lastly, the actual collection of breath can be tricky for some. And if collection isn’t done properly, the lab will reject it and you have to start all over again. With this in mind, detailed video instructions for test collection including prep diet can be found here.
Final Thoughts
Overall, test collection is nothing compared to struggling with a digestive disorder that no one, including your specialists, have any answers for. If you think you may have SIBO or have exhausted all your medical options and would like to get a second opinion, I’d love to help!
You can book an appointment here.
References:
Shah, Ayesha, Mark Morrison, and Gerald J. Holtmann. “Gastroduodenal “Dysbiosis”: a New Clinical Entity.” Current treatment options in gastroenterology 16.4 (2018): 591-604.
Rezaie, Ali, et al. “Hydrogen and methane-based breath testing in gastrointestinal disorders: The North American Consensus.” The American journal of gastroenterology 112.5 (2017): 775.