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Could It Be SIBO: Causes, Symptoms, & Treatment

Aug 04, 2022

Do you begin the day with a flat belly but end up looking and feeling pregnant (when you’re definitely not) as the day slowly comes to an end? Do you have tummy troubles that have you doubled over in pain one minute and running for the porcelain throne the next? Or do you end up with cramping pain that leads you down a road to nowhere and you simply wish you could have satisfying bowel movements? Maybe this has been your story for years now and you’ve figured out how to adapt. I want you to know that you’re not alone! Most of you suffering like this already have a diagnosis of IBS, which affects more than 25 million people in the US. That’s just the United States! In this article, we will discuss SIBO as a possible underlying cause of your IBS issues, what actually causes SIBO, its symptoms, and the usual conventional and functional medicine treatments. Keep on reading, friends! 

Okay, so SIBO. Here’s the deal. New research suggests that IBS can often overlap with more defined conditions, like small intestinal bacterial overgrowth (SIBO). In fact, upwards of 70% of people with IBS have undiagnosed SIBO. 🤯  


What is SIBO? How is it diagnosed?

SIBO is a serious condition that affects the small intestine. It is a form of dysbiosis, or imbalance in the gut bacteria. SIBO occurs when bacteria that normally grow in other parts of the gut start growing in the small intestine in larger numbers. The definitive number to diagnose SIBO is an overgrowth roughly two-to-three orders of magnitude higher than the amount that is normally found in this area of the small intestine. The problem is that aspirating the small intestines is not a very practical method and the usual breath testing common among functional medicine practitioners can vary wildly with both sensitivity and specificity. And none of the gastrointestinal specialists in my area offer breath testing. In most conventional cases, a treatment is offered “if the shoe fits.” 


The breath testing consists of consuming various carbohydrates that will then be available as food for bacteria in different locations along the digestive tract. By measuring how much gas is being produced, they can predict whether a patient has hydrogen-dominant or methane-dominant SIBO. As I mentioned, the tests can be misinterpreted and are not always accurate. 



Possible causes of SIBO

SIBO can be caused by anything that contributes to low motility or undigested carbohydrates. When the food doesn’t migrate down the intestines at normal speed and the transit time is prolonged OR the food isn’t broken down well, the bacteria are able to ferment more of the carbohydrates and they replicate and overgrow. 


  • Low stomach acid (usually from use of a PPI drug, such as Prilosec)
  • Low digestive enzyme production 
  • Sluggish thyroid function
  • Prolonged stress
  • Constant snacking 
  • Antibiotic use
  • Food poisoning 



Regardless of the cause, SIBO can lead to debilitating symptoms. The usually small number of bacteria in the small intestine enjoy their carbohydrate fiesta and the fallout from their bacterial party leads to excess fermentation in the intestines. As you can imagine, extra gas ends up distending the abdomen and contributing to the hallmark signs and symptoms of SIBO (which overlap with IBS):


  • Gas
  • Bloating
  • Diarrhea
  • Constipation (in some patients)
  • Abdominal pain 


A big takeaway here is that I suspect SIBO when someone can no longer tolerate raw vegetables or high-fiber vegetables. 




So there is this possible overgrowth of bacteria in a place that is really difficult to assess and the frustrating part is that the interventions and treatments are also difficult to assess. The primary goal of any SIBO protocol should be to eradicate the overgrowth while also allowing for the commensal (the “good guys”) organisms to thrive and not be collateral damage. The primary treatment modality is dietary restriction of (ding, ding if you guessed this already)... carbohydrates in an effort to “starve out the bad guys.” The logic is that if they don’t have enough food, then they’ll naturally die out. Makes sense, right? 


Conventional treatment for SIBO

 Traditionally trained gastroenterologists or primary care providers suspicious of SIBO usually opt for pharmaceuticals to eradicate the overgrowth. Rifaximin (Xifaxan) is the medication of choice plus or minus Neomycin. Neomycin is usually avoided because of the laundry list of possible side effects. I don’t know about you, but I don’t want to trade my abdominal pain for hearing loss. Is that just me?! The issue with prescribing Rifaxamin is two-fold. One problem is that it’s wildly expensive (I’m talking easily $600+ for one round of treatment) and insurance coverage isn’t great. The other issue is that insurance only covers it for IBS-D at this time. That’s IBS with predominantly diarrhea if you weren’t sure. 


This is crazy to me because SIBO with a methane-positive breath test can mostly cause constipation. And this is the more difficult one to treat. Multiple randomized controlled trials have revealed that it actually performs quite well in SIBO patients with constipation. The joys of insurance companies and trying to get medication approved… 


Side bar: When I was working through my SIBO issues many years ago, I was able to take two weeks of Rifaxamin (I obviously skipped the Neomycin), and I felt that it was only mildly successful. Keep reading below to understand why I think that was the case. 


A functional approach to SIBO

 Functional medicine appreciates the importance of acknowledging that SIBO is not necessarily “bad bacteria” but instead it’s the good guys in the wrong place. A functional medicine approach includes addressing the true root causes of SIBO and this is why I was ultimately successful in the long-term. 


  • Elimination diet or low-FODMAP diet 
  • Fiber supplements in those with constipation (specific supplements to help relieve constipation)
  • Antimicrobial herbs
  • Digestive enzyme and HCl support
  • Multivitamin 
  • B12 supplement
  • Probiotics (at a lower dose)
  • Gentle movement (such as yoga, walking) 
  • Mind-body techniques to improve digestion
  • Vagus nerve stimulation
  • Eating hygiene 
  • Water


Without addressing the true root cause of SIBO, which for most of my patients includes taking a long hard look in the mirror and addressing chronic stress, then most people will be in the revolving door of elimination diets and medication management. 


The beauty of functional medicine is that we collectively understand that you cannot heal in the same environment in which you became ill. Bombing the gut with antimicrobials and sending a patient on their way is definitely not the answer. We must encourage our patients to consider what is happening in their life (such as stress lowering their stomach acid) that allows the microbiome to become so imbalanced. And then we need to encourage and inspire them to take the necessary steps to make changes. When viewed this way, SIBO can be to  many patients a wake up call that what they’re doing isn’t serving them. And when the fog lifts and the bloating and pain go away, they are left with better self-care and improving coping techniques. 


If you have any more questions about how the gut-brain axis can wildly influence your overall health, please check out my other blog post.