Understanding SIBO Testing: What, When, and Why

Receiving a firm and accurate diagnosis of SIBO (small intestine bacterial overgrowth) can be a real challenge. SIBO is a digestive condition that is often undiagnosed and commonly overlooked. SIBO testing doesn’t always happen when it needs to. How can this happen during a time of growing scientific advancements? 

A big problem with diagnosing SIBO is testing. Who to test, what time is best to test, how to test, types of tests, and how to interpret the findings of the SIBO breath test.

SIBO research is evolving every day and it may be challenging for practitioners to keep up to date with the best methods. And unfortunately, there is no typical presentation for SIBO! 

In most patients, it is caused by multiple types of bacteria that are displaced and can present with a variety of symptoms. However, it is important that you know what to look for in a SIBO test result and are well prepared when working with a practitioner. 

Let’s get started and jump into an overview of SIBO and the main types of testing.

What is SIBO?

First off, SIBO stands for Small Intestinal Bacterial Overgrowth. This means there is an accumulation of bacteria in the small intestine (SI). Basically, bacteria that normally lives in the colon, moves up to where they don’t belong to colonize in the SI region. 

Normally, the colon is populated with trillions of different bacteria and the SI has significantly fewer (about 10,000 total). In a healthy GI tract, besides a variety of microbes, there are many common gases produced like nitrogen, CO2, and hydrogen. 

However, during bacterial overgrowth, different gases, like methane and hydrogen, are elevated. It is important to note that these gases are produced by bacteria, not humans. The levels of hydrogen and methane contribute to the symptoms, like gas and bloating, that people experience with this often confusing and frustrating condition. 

The Problem with SIBO

These little gas-releasing bacterial parties can interfere with normal digestion of food and may damage the lining of the small intestine (also known as leaky gut syndrome.)

Some examples of the problems a bacterial imbalance can cause include: 

• Bacteria use the food we eat as fuel, leading to nutrient deficiencies such as iron and B12. Deficiencies of vitamins and minerals can cause anemia, low energy, and overall body pain. 
• Due to the damage of the gut, food is unable to be absorbed properly through the lining of the SI.
• GI discomfort and symptoms (we will tackle these later on!).
• Decrease fat absorption which can lead to deficiencies of fat-soluble vitamins. This is often associated with fatty, foul-smelling stools. 
• Large food particles aren’t easily broken down and damage the gut lining, causing an immune reaction. Bacteria may enter the bloodstream and cause immune system antibodies to attack these evil bugs. This can cause chronic fatigue, body pain, and liver damage,

Different Types of SIBO

There are three main types of SIBO: methane, hydrogen, and hydrogen sulfide. These are the three main gases produced by certain bacteria and archaea. 

 1) Methane Dominant 

Your intestinal microbiome contains organisms called archaea. These really aren’t bacteria but are single-celled organisms without a nucleus. A type of archaea species called methanogens, convert hydrogen gas into methane in the large intestine. 

Most research has shown the role of methane gas in slowing down GI transit time. This may lead to constipation (predominant symptom) and excessive bloating. It may be more challenging to resolve methane dominant SIBO because these bugs tend to be antimicrobial/antibiotic-resistant. 

Symptoms of Methane SIBO:

• Constipation and slow transit time
• Bloating
• Gas
• Abdominal Discomfort

2) Hydrogen Dominant

Hydrogen dominant SIBO is the result of carbohydrate-fermenting bacteria that produce hydrogen gas in the SI. These hydrogen gases can be absorbed and exhaled or they can be converted into methane. Remember, we all create gas from our living microbes in the colon. 

The problem arises when we have too many microorganisms, producing too much gas in the small intestine. Your small intestine is sensitive to these high levels of hydrogen production, which leads to uncomfortable GI symptoms. . 

Symptoms of Hydrogen SIBO: 

• Diarrhea (most common)
• Excess hydrogen tends to cause fast transit time and loose stools
• Bloating
• Abdominal distension and discomfort

3) Hydrogen Sulfide

This type of SIBO is the new kid on the block, less common and less understood. Sulfur is an essential mineral that is used in all living cells. It plays a role in amino acid composition, energy production, and cellular response. 

In a healthy person, small amounts of hydrogen sulfide is made, and our body excretes the byproducts of sulfur. When high amounts of hydrogen sulfide are made, our gut panics because it is overwhelmed by detoxifying. These high amounts can become very problematic.

Symptoms of Hydrogen Sulfide SIBO: 

• Rotten egg smelling gas
• Fatigue
• Diarrhea or constipation
• Brain fog 
• Leaky Gut
• Belching
• Intolerance to sulfur-containing foods (eggs, onions, cruciferous veggies, garlic, etc.) 

Testing for SIBO

After going through your symptoms, health history, and physical exam, your practitioner may recommend additional testing if he or she is suspecting SIBO. 

Hydrogen and Methane Lactulose Breath Test

A breath test is a gold standard for non-invasive SIBO testing by measuring hydrogen and methane gas production. After the gases have been produced by the bacteria, they diffuse into your bloodstream and then to your lungs for expiration. 

Essentially, to complete a test you will consume a sugar substrate (either lactulose or glucose) and breathe into a breathalyzer device at specific intervals. The sugar will be fermented by your gut bacteria and produce gases that will travel to your lungs. The test measures the gases in your breath sample and the amount of time it takes the gases to be produced.

It is important to look at spikes in your gas levels before the sugar substance reaches your colon to determine if there is an overgrowth throughout the SI. Keep in mind, you should test for both hydrogen and methane because methane-producing bacteria can consume hydrogen gas to produce methane. 

Types of tests: 

• Lactulose Breath Test: Humans can’t absorb or digest lactulose. But, bacteria have enzymes that break down lactulose and make gas. When there is an overgrowth, this will be reflected in the levels of gases. Lactulose won’t be absorbed until it reaches the gut bacteria, usually in the lower part of the SI.
• Glucose Breath Test: Glucose is absorbed in the first parts of SI, therefore if there are levels of hydrogen or methane during the test, this reflects an overgrowth in the high part of the SI. Unfortunately, this test doesn’t show if SIBO is present at the end of the small intestine. 

Inconclusive Test for SIBO

But what if your breath test shows normal hydrogen and methane gases? Do your symptoms show your gas is linked to sulfur? This may be because you have hydrogen sulfide overgrowth. The popular SIBO breath test is not able to detect hydrogen sulfide gas yet. 

However, stay calm, now the science becomes confusing. In simple terms, if you have lots of hydrogen sulfur bugs, they can compete with the methanogens (methane-producing bacteria) and consume hydrogen to produce more hydrogen sulfide. Due to this competition and consumption of gases, you may have a flat line graph from the breath test. 

Good news though! You can work with your practitioner to find out if your symptoms are due to hydrogen sulfide SIBO and treat it naturally – especially since rotten-egg smelling gas is a telling symptom.

Testing and Treating SIBO

If your gut is functioning correctly, different gases are maintained in healthy amounts from digestion and fermentation. If there is an increase in hydrogen, hydrogen sulfide, and methane gas is produced, you might be suffering from SIBO. 

Remember than many people may be suffering from methane AND hydrogen-producing SIBO. Testing can help distinguish the severity; however, it is best to tackle your SIBO by addressing the symptoms and using testing to confirm. 

By working with a practitioner, you can help overcome your abdominal discomfort and be one step forward on the journey to a healthy, more enjoyable life! Let us work together to bring the balance back to your small intestine, gut health, and body.