SIBO: The Most Common Cause of IBS (Part 1)

SIBO: The Most Common Cause of IBS (Part 1)

Did you know one of the most frustrating diagnoses a doctor can give is irritable bowel syndrome (IBS)?

This is because IBS has many causes. And you have to understand what’s causing your IBS in order to heal your IBS.

The number one cause of IBS that I see at my clinic is small intestinal bacterial overgrowth (SIBO).

What exactly is SIBO?

What are the symptoms of SIBO?

What causes SIBO?

We’ll explore the answers to these questions in this blog post.

What Is SIBO?

Small intestinal bacterial overgrowth (SIBO) is what the name suggests – it’s a condition where there are more bacteria in your small intestine than there should be.

Your small intestine should have fewer bacteria than your large intestine in order for your digestive system to function properly. When there’s an overgrowth, your body won’t be getting the proper nutrients it needs which can lead to SIBO symptoms.

SIBO may lead to:

  • IBS (irritable syndrome)
  • Leaky gut (intestinal permeability)
  • Vitamin deficiencies and malnutrition

These problems can arise from any type of SIBO. Let’s explore the different types of SIBO first and then learn about specific SIBO symptoms.

What Are the 3 Types of SIBO?

The harmful bacteria in your small intestine are nourished through carbohydrates from your food. Those carbs are then fermented by the bacteria into a specific gas. The gas by-product will determine what type of SIBO you have.

The three types of SIBO include:

  • Hydrogen dominant SIBO: Produces hydrogen gas
  • Hydrogen sulfide dominant SIBO: Produces hydrogen sulfide gas
  • Methane dominant “SIBO”: This SIBO was renamed intestinal methanogen overgrowth (IMO) by Dr. Mark Pimentel. It produces methane gas.

What’s the deal with IMO?

Well, IMO is no longer referred to as SIBO because the microorganisms that produce methane aren’t bacteria. They’re archaea (specifically methanobactersmithii). And in addition to the microorganisms not being bacteria, they’re also not solely located in the small intestine (as the term SIBO implies). Methane gas can be produced in the large intestine AND small intestine. So, that’s why it’s called IMO – it simply doesn’t meet the criteria of SIBO.

The other two forms of SIBO are hydrogen sulfide dominant SIBO and hydrogen dominant SIBO. They both are the result of gas production from bacteria, and the microorganisms involved are only found in the small intestine.

Now that we know the three types of SIBO, let’s explore the symptoms you may experience if you have SIBO.

What Are the Symptoms of SIBO?

SIBO can cause a variety of symptoms. But just because you’re experiencing these symptoms doesn’t mean you have SIBO. Our bodies are unique, so it’s important to understand the root cause behind the symptoms you’re experiencing.

Here are common SIBO symptoms:

  1. Bloating: progressively worsening throughout the day
  2. Cramping/ Abdominal pain
  3. Gas/Flatulence
  4. Nausea
  5. Constipation: most common with methane gas IMO
  6. Diarrhea: most common with hydrogen and hydrogen sulfide gas SIBO
  7. Weight loss
  8. Steatorrhoea: fat in the stool due to poor digestion
  9. It can also cause full body symptoms such as brain fog, acne, rosacea, and fatigue

These symptoms, as difficult as they are to deal with, unfortunately do not explain the root cause of SIBO. So what exactly causes SIBO, i.e. how did that harmful bacteria get lodged in the small intestine to begin with?

What Causes SIBO?

SIBO has many causes, but let’s look at five common causes I see in my practice.

1. Food Poisoning and Slow Intestinal Motility

So you got sick while on vacation or from a new restaurant… Your symptoms probably last only a few hours to a couple of days. But did you know that the food poisoning you experienced could actually have long-term effects?

Food poisoning is also known as bacterial gastroenteritis. It’s the number one cause of SIBO that I see in my practice. Let’s break down what happens when your gut comes in contact with harmful bacteria.

    • The bacteria that commonly cause food poisoning include Salmonella, Campylobacter, Staphylococcus aureus, and Bacillus cereus. 
    • These bacteria causing your food poisoning may release a toxin called Cytolethal Distending Toxin (CDT). 
    • Your body’s immune system produces antibodies to get rid of CDT, but these antibodies can also mistakenly cross-react with a healthy protein in your intestinal wall called vinculin.
    • The reaction between vinculin and your antibodies leads to damage to your migrating motor complex (MMC), an important built-in micro-machine in your intestines that functions to clean out your small intestine. It does this through electromagnetic waves that increase contractions so that your small intestine can push out your waste into your large intestine where it belongs.
    • So if your MMC isn’t functioning properly, it is a big deal as you won’t have the tools to sweep out harmful bacteria out from your small intestine into your large intestine.
    • These harmful bacteria can then remain stuck in your small intestine causing a host of problems as listed above

Overall, food poisoning can lead to a chronically slower motility of the small intestinal which increases your chances of SIBO.

2. Antibiotic Overuse

While specific antibiotics can be used to treat SIBO, taking too many rounds of antibiotics within your lifetime can cause SIBO.

Antibiotics eliminate both harmful and beneficial gut bacteria which leads to an imbalanced gut microbiome. This imbalance means you may lack enough of the good bacteria to crowd out the bad guys, which can lead to an overgrowth, SIBO. You’ll learn about important SIBO herbal treatments in Part 2 of this series. But I want you to know that if you’re hesitant to take prescription antibiotics, there are herbal therapies you can consider that are known to be as effective.

3. Anatomical Causes From Surgery or Injury

Your gut’s structure and overall anatomy are important in making sure that your food digests properly. Some conditions from trauma or anatomical changes can interfere with your digestive system’s ability to process foods. Some of these causes include:

    • Scar tissue from abdominal surgery or radiation
    • Removal of parts of your small intestine
    • Certain medical conditions like Crohn’s disease and Celiac disease

Scar tissue can also interfere with your MMC leading to slow intestinal motility and eventually SIBO.

4. Stress

With our fast-paced, always-on-the-go culture, it’s really common to be consistently stressed. Being chronically stressed can not only affect your health in general but it can do a number to your digestive system.

Stress can contribute to digestive health problems because when your body’s stressed your nervous system remains in a fight-or-flight mode even while you’re eating. Your body gets the message to shunt your blood and nutrient supply away from your digestive tract to your heart and large muscle groups (so you can run from that tiger in the jungle). This leads to a decrease in digestive enzymes, stomach acid, and bile production – chemicals that your body needs in order to digest foods properly.

Your body needs stomach acid and digestive enzymes to break down food properly and suppress the growth of harmful bacteria. Bile also helps in digestion by breaking down fatty acids and preventing the growth of harmful bacteria too.

Additionally, stress can thin and erode the protective mucous membrane which lines the stomach and intestines. Damage to this important mucous layer can lead to symptoms such as heartburn/acid reflux and GERD, digestive pain, ulcers, and leaky gut syndrome.

If you’re dealing with high amounts of stress, you can work with your naturopathic doctor or therapist to manage these symptoms in order to improve your digestive health and overall lifestyle.

5. Acid-Blocking Medications

Acid blocking medications like proton pump inhibitors (PPIs) are very common when used to treat heartburn. However, while these medications can provide temporary relief, they may lead to harmful long-term effects like SIBO.

Acid-blocking medications can contribute to SIBO because they block the acid pumps in your stomach. Your gut relies on acid to destroy harmful bacteria by creating an acidic and inhospitable environment, it’s part of your gut’s immune system. Medications like PPIs and acid-blockers interfere with this protective acidic environment and increase your susceptibility for bacterial overgrowth and infections.

While there are many causes of SIBO: slow intestinal motility through food poisoning, antibiotic overuse, anatomical conditions or abdominal scar tissue, stress, and acid-blocking medications being five of the most common causes; It’s critical to understand which type of SIBO you have (hydrogen, hydrogen-sulphide, or methane dominant), as well as the root cause of your SIBO in order to get proper treatment and importantly to prevent SIBO from recurring. 

Let’s Understand the Real Cause of Your Digestive Upset

Dealing with IBS and SIBO can be frustrating… 

I want you to know that you’re the expert on your body. You’re not imagining your symptoms. And I can use my expertise in digestive health to get the answers you deserve.

So if you’re interested in partnering together to understand the root cause of your digestive upset, schedule a free consultation call with me here.

I believe in you!

Dr. Laura Brass


P.S.: Are you interested in learning about SIBO testing and treatment protocols? Stay tuned for Part 2 of this blog post series.


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