SIBO: The Complete Guide To Small Intestinal Bacterial Overgrowth

Today we will be covering everything you need to know about small intestinal bacterial overgrowth. This complete guide to SIBO, in all it’s 10,000 plus words glory, covers the key points on SIBO including testing options, conventional and alternative treatments and the common underlying causes of this gut disorder.

Small intestinal bacterial overgrowth, also known as SIBO, is a  digestive disorder that is becoming more widely recognised in the digestive health community. It is associated with a wide range of health issues such as nutrient deficiencies, intestinal hyperpermeability (aka leaky gut) and even liver damage. 

Read on to learn more about this digestive imbalance or if you know what you are looking for you can use the table of contents below. 

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What is SIBO

First off a definition is helpful. 

SIBO is much like it sounds. An overgrowth of bacteria in the small intestine. There has been debate over what the exact cut off is for SIBO. The most widely held definition is a growth of bacteria greater than 1,000,000 (thats 10 to the power of 5) colony forming units per ml while some researchers are pushing to reduce that number down to 10,000 (10 to the power of 3) colony forming units (1).

Either way the definition stands. 

More bacteria in the small intestine than there should be. 

Originally the thinking was that the small intestine was sterile. 

As our technology to assess microbes has improved we have learned that a healthy small intestine has a microbial community. That said, the small intestine has far less bacteria when compared to the large intestine due to a range of factors including the flow of the contents (known as peristalsis – we will be coming back to this concept later) as well as bactericidal substances such as bile acids keeping the level of microbes low (2).

Why is SIBO an issue?

Small intestinal bacterial overgrowth is associated with a whole range of comorbidities – additional conditions – as well as changes to the digestive tract structure and function.

SIBO may be responsible for 

• Vitamin deficiencies
• Malabsorption 
• Malnutrition 
• Intestinal permeability (aka leaky gut)
• Liver damage 
• Changes in bowel pattern
• Abdominal pain (and many other symptoms!)

Symptoms Of SIBO 

Now that we have covered the different types of SIBO we can talk about the different symptoms that digestive health clinicians should be familiar with. While no specific symptom can determine whether SIBO is present the following symptoms should raise some red flags and lead to SIBO testing. 

Some of the following symptoms can be present in both methane dominant SIBO and hydrogen dominant SIBO. Other symptoms are more common in one or the other. 

But remember, symptoms aren’t enough to diagnose which type of SIBO you really need to test if you suspect!

Symptoms (3).

• Bloating – common in methane and hydrogen dominant
• Flatulence – common in methane and hydrogen dominant
• Abdominal pain – common in methane and hydrogen dominant
• Tenderness – common in methane and hydrogen dominant
• Weight loss – common in methane and hydrogen dominant
• Steatorrhoea (aka fat in the stool due to poor fat digestion) – more common in hydrogen dominant SIBO
• Diarrhea – more common in hydrogen dominant SIBO
• Constipation – more common in methane dominant SIBO

Different types of SIBO 

While the umbrella concept of SIBO is simple enough to understand – an overgrowth of bacteria in the small intestine. The different forms of SIBO can make the picture slightly more complicated. And what can make it slightly more complicated is the fact that a number of different types of SIBO can be present at the same time. 

Confused yet? 

Don’t be.

We will take each different type of SIBO one at a time.

Hydrogen dominant SIBO 

In the human gut certain bacteria produce certain gases as a by-product of their growth and replication. Hydrogen production is common among bacteria that make up the gut microbiota. In a healthy gut hydrogen producing bacteria reside mainly in the large bowel. However, in the context of SIBO, certain hydrogen producing bacteria can take up residence in the small bowel and become what we call hydrogen dominant small intestinal bacterial overgrowth (4). 

The testing section of this guide will outline how to test for hydrogen dominant SIBO by using certain sugars that these particular bacteria use as a food source. 

Methane dominant SIBO

Moving onto the second form of SIBO we come to methane dominant SIBO. 

Where hydrogen production in the human gut can come from a wide variety of bacteria, methane production is limited to just a few. These are known as methanogens, and are technically not bacteria, but archaea. The most common methane producer in the human gut is known as Methanobrevibacter smithii. Methanobrevibacter smithii (and other less commonly found methane producers) use hydrogen – remember hydrogen is in good supply in the gut – to make methane or CH₄ (4).  

The number one symptom of methane dominant SIBO is constipation (5).

If a patient is presenting with bloating, abdominal distention after meals and constipation I would immediately be thinking methane-dominant SIBO. 

The next step her, after a thorough intake and history, would be ordering a SIBO breath test to confirm this suspicion. 

More on that soon

Mixed SIBO

The third type of SIBO is what is known as mixed type SIBO. 

I’m sure that some of you have already put two and two together. If methane producers use hydrogen to make methane then there must be hydrogen producing bacteria present as well. 

When we test for SIBO using SIBO breath tests there is the possibility that both methane and hydrogen producers are found in the small bowel leading to the mixed SIBO diagnosis. 

It is also possible for the methane producing archaea to be using all of the hydrogen (produced by the hydrogen bacteria). It is common to test for and find methane dominant SIBO, treat the methane producers successfully, then retest and find hydrogen dominant SIBO. 

What has happened here, most likely, is the methane producers have hidden the hydrogen producers by using up all of their byproduct – hydrogen. 

Hydrogen Sulfide dominant SIBO

A final form of small intestinal bacterial overgrowth is called hydrogen sulfide dominant SIBO. 

We have covered hydrogen sulfide production in the large bowel before by covering the different bacteria that form hydrogen (Desulfovibrio and Bilophila) as well as their implication in leaky gut and inflammatory bowel disease.

Now let’s talk about hydrogen sulfide production in the small intestines.

The main problem with diagnosing hydrogen-sulfide dominant SIBO is that there is, currently speaking, no test available that screens for this gas. Our best people are working on that as we speak.

The lack of testing for hydrogen sulfide SIBO is problematic to say the least. 

In one recent study the researchers found that screening for hydrogen sulfide was better correlated with patient symptoms. Patients with higher levels of hydrogen sulfide had more diarrhea, constipation, abdominal pain and even fatigue (6).

Below is an image that shows some of the clinical associations between the different gases and the possible mechanisms – ie how they affect the body.

Fungal SIBO – or should we say SIFO

This may be an article for a different time. 

Small intestinal fungal overgrowth (such as Candida) is not commonly talked about. The idea that bacteria can take up residence in the small bowel should be a clear sign that fungal overgrowth can occur as well (7).

If this is the case then proper fungal treatments may be necessary when addressing SIBO cases.

Underlying Causes of SIBO

What sets the stage for bacterial overgrowth in the small intestine? The answers can be numerous and much like the different types of SIBO a number of underlying causes can be present at the same time. 

As SIBO is relatively recent to the game (remember back when all gut issues were Candida infections?) the underlying causes don’t seem to be addressed by many people that treat SIBO. Many times it is simply antimicrobial herbs, possibly followed by probiotics and you’re done. 

As the underlying causes that led to SIBO are often not addressed with this approach the relapse rates can be high. 

These causes for SIBO can be broken down loosely into three categories including disorders of protective antibacterial mechanisms, anatomical abnormalities and motility disorders. Remember there may be one or many predisposing factors that can encourage small intestinal bacterial overgrowth (8).

Let’s cover each category one by one. 

Causes of SIBO Category 1. Disorders of protective antibacterial mechanisms

Low stomach acid 

Known in the medical world as achlorhydria may lead to SIBO. A healthy stomach is acidic. Damn acidic! This helps to kill off many of the microbes that are present in your food, on your pets (think of a dog’s love for licking your face), in unfiltered water (beaver fever is usually Giardia, contracted from river and pond water) and many, many other places.   

So low stomach acid can cause SIBO, but what causes low stomach acid? 

The first offender are pharmaceutical drugs known as proton pump inhibitors – or PPIs. These drugs effectively shut off the production of acid in the stomach. Originally this class of drugs were prescription and only intended for short-term use. Now many of them are available over the counter and are commonly taken long term. 

PPIs are associated with small intestinal overgrowth and there is high quality science to back this up, including two meta-analyses (one from 2013 and one from 2017).  

PPIs are also associated with other non-SIBO related issues (seen in the image below) including magnesium and vitamin B12 deficiencies and possibly even Clostridioides difficile (previously Clostridium difficile), chronic kidney disease and dementia (11).

While there may be a place and time for these commonly used drugs they, much like antibiotics, may be overprescribed.

Exocrine pancreatic insufficiency

This is a less-clear underlying cause of SIBO but worth covering anyway.

SIBO appears to be more common in patients with chronic pancreatitis (12).

The thinking here is, due to the reduced function of the pancreas and it’s antibacterial proteolytic enzymes, bacteria is permitted to grow in the small intestine (8).

There would be other symptoms associated with chronic pancreatitis that a primary care physician would be well aware of and capable of managing.

Immunodeficiency syndromes

Finally immunodeficiency syndromes including IgA deficiency and even AIDS can predispose one to SIBO (13, 14).

Narrowing in on the selective IgA deficiency we can see that it is one of the more common primary immunodeficiencies, which may predispose one to mucosal infections (SIBO would fit in here) as well as atopy and even autoimmune diseases (15, 16). 

Causes of SIBO Category 2. Anatomical Abnormalities 

Moving onto the second category of conditions we can see that anatomical abnormalities can predispose one to small intestinal bacterial overgrowth. These conditions include small intestinal obstruction, diverticula, fistulae, surgical blind loop and previous ileo-caecal resections (8).

This is a fairly simple concept to understand but one that is often overlooked. Anything that impairs the flow through the small intestinal lumen will lead to stagnation and bacterial overgrowth. 

Often these conditions are associated with previous surgeries (17).

One anatomical abnormality that is not necessarily associated with previous surgeries is diverticular disease. Diverticular disease is associated with slower oral-coecal transit time – remember anything that slows down the flow through the intestines may predispose you to SIBO (18).

One study found that transit time was delayed in 74.44% of patients with diverticulitis and that 58.88% of patients from the trial had SIBO diagnosed by a lactulose breath test (19).

Ileocecal valve pressure

The ileocecal valve connects the end of the small bowel to the start of the large bowel. For quite some time, poor ileocecal valve function it has been theorised to be involved in SIBO. As our technology to assess what is actually happening in the gastrointestinal tract develops we are started to get a clearer picture of how important the ileocecal valve is in health and disease. 

We know that the large bowel has significantly (let’s say exponentially!) more microbes when compared to the small intestine. The ileocecal valve keeps the microbes from being refluxed from the large bowel back into the small bowel. You can think of it as a gatekeeper. It allows contents to flow in one direction only. 

SIBO patients were shown to have lower ileocecal valve pressure, leading to a ‘lazy’ ileocecal valve and the possibility that microbes could make it back into the small intestine. These microbes, if given the right environment, could then overgrow into a case of SIBO (20).

Causes of SIBO Category 3. Motility Disorders

The third category of SIBO causes include a range of gastrointestinal motility disorders. Again we can see the same pattern emerge here with poor flow through the small intestine leading to bacterial overgrowth. 

These conditions include

• Scleroderma
• Autonomic neuropathy in diabetes mellitus
• Post-radiation enteropathy
• Vagal nerve dysfunction
• Migrating motor complex dysfunction

Post Infectious SIBO

Irritable bowel syndrome can be broken down into a number of different sub-categories (constipated, diarrheal, mixed and post-infectious) but the idea that infections could predispose you to SIBO is rather new and still needs to be worked out by the scientific community. 

Still, I felt it was worth including in this SIBO guide because it makes so much sense. 

How many people have developed SIBO after acute gastroenteritis. Maybe it was during a trip to a third world country or maybe (as in my experience) it was from consuming contaminated drinking water.   

So what does the literature say on this concept? 

First off, there has been new developments in diagnosing post infectious IBS. 

After being exposed to any number of different bacterial infections including Campylobacter jejuni, Salmonella, Escherichia coli and Shigella different toxins have been found including cytolethal distending toxin A, B and C. Our body then produces antibodies against these toxins. 

It all makes sense so far right?

Then, possibly due to the molecular mimicry model of autoimmunity, there is some cross reactivity and the antibodies start targeting a very important protein found in the gut called vinculin. 

Vinculin has a number of key roles in the gut. It is involved in neuronal cell motility, and gut wall formation (21). 

This is pretty big news. 

Infections by certain common bacteria can predispose you to poor gut motility, a hall-mark of SIBO!

Comorbidities associated with SIBO

Small intestinal bacterial overgrowth is associated with a long list of other health issues. Some may be caused by SIBO, some may be caused by the same thing that caused SIBO (a bit of a tongue twister there). 

The image below lists some of the more common conditions associated with SIBO. 

Intestinal permeability

Intestinal hyper-permeability (aka leaky gut) is associated with small intestinal bacterial overgrowth. 

In fact, SIBO may be causing leaky gut in certain people. 

One small study found that clearing the bacterial overgrowth in SIBO patients improved their leaky gut. 

Plus, increased intestinal permeability – leaky gut – is associated with a number of commonly seen issues in SIBO such as food intolerances and histamine sensitivity.

Cirrhosis/Liver damage

Liver damage may not be the first thing you think of when you think of SIBO but the connection between the gut and liver is well documented. 

Seeing as the liver is connected to the gut via the portal vein, and receives a continuous supply of nutrient and microbe laden blood, this should be fairly obvious. 

In cases of SIBO and leaky gut the liver takes on an extra load of endotoxin (also known as lipopolysaccharide or LPS) laden bacteria which can promote localised inflammation, liver cell damage and even body wide inflammation (24).

A recent systemic review with meta analysis, published in the European Journal of Gastroenterology & Hepatology, concluded that there was a ‘significant association between NAFLD (non-alcoholic fatty liver disease) and SIBO was observed in this meta-analysis’

Malnutrition

Both fat soluble vitamins including vitamin D, vitamin E and possibly even vitamin A may be deficient in SIBO cases whereas vitamin K levels may be normal or even raised. This vitamin is synthesised by bacteria so this makes sense when you think about it.

Other nutrients which may be low in SIBO cases include vitamin B12 (keep an eye out for megaloblastic anaemia and the associated polyneuropathy) as well as iron deficiency which may lead to microcytic anaemia. 

There are a few reasons to explain these possible nutrient deficiencies associated with SIBO including bacterial metabolism, the damage that SIBO can cause to the mucosa of the small intestine and even the restricted diets that many people use to either treat their SIBO or minimise their symptoms. Finally chronic diarrhea and fat malabsorption may lead to nutrient deficiencies (26).

Inflammatory Bowel Disease

Are inflammatory bowel disease (IBD) and SIBO connected in any way? 

We know that IBD, including Crohn’s disease and ulcerative colitis, have an altered microbiota in the large bowel that could be driving the disease (more here and here). We also know that SIBO is a condition of an altered microbiota in the small intestine. But is there an overlap? 

One systemic review with meta-analysis (very high level science) found that SIBO was present in 22.3% of patients with inflammatory bowel disease. Looking into the subtypes of IBD they found that SIBO positive Crohn’s patients did not have elevated CDAI (Crohn’s disease activity index) compared to Crohn’s disease patients without SIBO. One study included in the review found that there was significantly higher levels of calprotectin (which can be tested by your doctor and is also found on the GI-MAP) in SIBO patients with Crohn’s disease compared to SIBO negative Crohn’s disease patients.  

So what do we make of this?

It is early days in the SIBO and IBD world. The study covered above was published this year (2019) and only included 1175 IBD patients. The second issue here is that the studies included only used one type of sugar in their SIBO breath test (we’ll cover why that is an issue later on) so they may be underreporting the incidence of SIBO in IBD. 

For now I think it is worth keeping in mind that if you have IBD then it is possible that SIBO is also present as well. Treating your SIBO (if present) may improve some of your gut symptoms but current thinking is that it is not a driver of IBD. 

Again this may change as we learn more. 

Irritable Bowel Syndrome

Irritable bowel syndrome has been correlated with SIBO for quite some time now. It is quite common for patients that had originally been diagnosed to have SIBO and, when treated, many of their symptoms improve. 

The question is, how common is SIBO in IBS and if someone has SIBO do they still have IBS?

The answer to the first question varies depending on which study you read.

• One of the most recent systemic review with meta analysis found SIBO to be present in over ⅓ of the patients with IBS
• Another, older systemic review with meta-analysis found that SIBO was present in 54% of IBS patients when using a glucose or lactulose breath test but only 4% when using the gold standard SIBO test, aspirate and culture.

The list of papers linking IBS to SIBO could go on and on.

I’ll leave it to the researchers to work out exactly how strong the connection is between the two gut disorders. For now it’s worth pointing out that if you have been diagnosed with IBS and fit the symptom picture of SIBO it may be worth getting tested to rule it out. 

Diabetes

Diabetes, both type 1 and type 2, are possible comorbidities associated with SIBO. 

In type 2 diabetes, the more common of the two, the poor blood sugar control (both hyperglycaemia and hypoglycaemia) can alter the gut motility. Type 2 diabetes have been shown to have slower oral-cecal transit time and higher rates of SIBO (31).

Rosacea 

Does SIBO cause rosacea or are they simple correlated?

One study found that SIBO was much higher in patients with rosacea. Plus when they treated and cleared the SIBO the skin condition cleared or greatly improved in over 90% of the patients.

True it was a small study and there is not much science to confirm these results but it does make you wonder. The gut-skin axis may be the driver in at least some people with rosacea. 

We have covered that particular study in more depth here for your to read at your convenience. 

Diverticular Disease

Most people would think that diverticulitis is associated with a low-fiber diet and much of the research is confirming that suspicion. While there is very little research connecting diverticulitis and SIBO, other predisposing factors for diverticular disease such as motility disorders (slowed transit time through the intestines) is a major factor that leads to SIBO in the first place (as we discuss here). 

One study looking into the connection between SIBO and diverticulitis found that 58.88% of patients with diverticulitis had SIBO using the lactulose breath test – don’t forget here that the lactulose breath test can miss some cases of small intestinal bacterial overgrowth as we covered in the testing section.

The same study also found that treating SIBO in patients with diverticulitis resulted in significantly improved symptoms.

Bacteria Found in SIBO Patients

So we now know that SIBO is an overgrowth of bacteria in the small intestine but what types of bacteria are responsible? 

This question is harder to answer than you might think.

A number of bacteria have been found in SIBO cases via duodenal aspirate and culturing including 

• Streptococcus
• Enterococcus
• Klebsiella
• E. coli

For SIFO it was predominantly Candida species of fungus (34).

Other bacteria include gram positive, aerobic or facultative anaerobic bacteria such as:

• Staphylococcus
• Micrococcus
• Lactobacillus
• Corynebacterium
• Bifidobacterium

Gram positive anaerobic bacteria:

• Fusobacterium
• Peptostreptococcus

Gram negative, aerobic or facultative anaerobic bacteria:

• Proteus
• Acinetobacter
• Enterobacter
• Neisseria
• Citrobacter

Gram negative, anaerobic bacteria

• Bacteroides
• Clostridium

References for bacteria found in SIBO (35, 36).

This list of bacteria associated with SIBO was put together from microbes found using the culture and microscopy techniques – basically sampling the small intestine and trying to grow what you have sampled. 

The real problem here is that not every microbe can be cultured! 

The percentage of microbes that cannot be cultured ranges from paper to paper (from 20-60% all the way up to 80%) although this number changers as our culture techniques improve (39).

To date there has only been a few studies using DNA based (non-culturable) assessments of the microbiota in SIBO patients. 

One study sampled the jejunum (the middle section of the small intestine) from 20 patients which was then cultured to diagnose SIBO (remember over approximately 10 to the 5th factor – 10 to the 7th factor would indicate an overgrowth). They also assessed the samples using a common DNA based assessment known as 16S ribosomal RNA – I think of this almost as a unique fingerprint that each bacterial genera has. A great way to assess bacteria without culturing. 

The most abundant microbes were similar to bacteria found in the mouth including

• Streptococcus (28%)
• Prevotella (13%)
• Veillonella (7%) 
• Fusobacterium (6%)
• Haemophilus (5%) 
• Actinomyces (3%)
• Rothia (2%)
• Leptotrichia (2%)
• Gemella (2%)
• Neisseria (2%).

As well as other bacteria including a few from the Proteobacteria phylum which we have covered before including: 

• Escherichia (7%)
• Klebsiella (2%),
• Citrobacter (2%)
• Actinobacillus (1%) 
• Enterobacter (1%)
• Bacteroides (1%) 
• Lachnoclostridium (1%)

The study concluded that few to no colonic bacteria were found in the jejunum in patients with SIBO. We will circle back to this when we talk about different causes for SIBO.  

Another recent DNA based study found an increase in the Proteobacteria phylum in SIBO patients and a decrease in the Firmicutes phylum. They also found a decrease in bacterial diversity in SIBO patients as well.

The image below shows DNA based assessment of patients without SIBO (the 0’s along the x axis) as well as upper aerodigestive tract SIBO (the 1’s) and coliform SIBO (the 2’s). 

Testing For SIBO

Testing for SIBO is complicated.

To date there is not one test that is as specific and sensitive as many clinicians (myself included) would like. Each and every one of the SIBO tests available are unreliable in their own special way.

Before we get into the different testing options let’s cover exactly what I mean by specific and sensitive. 

Specificity and Sensitivity in Testing

Specific testing. A test that is highly specific means that there is a very low chance of what it known as a false positive. A false positive in the pathology world is when a test comes back positive for a marker (in this case we are talking about SIBO) but it is wrong. 

Definitely not what we want.

With tests that have low specificity we get these false positive test results. In the case of SIBO if the testing came back with a false positive you might end up treating SIBO when in fact there was no SIBO! 

Sensitive testing. On the other hand there is the concept of the sensitivity of a test. Tests that are highly sensitive rarely miss. Highly sensitive testing means there is a low chance of a false negative (a false negative is when the test says there is no infection when in fact there is). In the case of SIBO a highly sensitive test would catch SIBO every time. On the other hand testing that has poor sensitivity (meaning it has low sensitivity) would miss SIBO even when it was there!

Again not what we want. 

So circling back to the point above, currently we don’t have one readily available test that is both highly specific and highly sensitive. Let’s cover what we do have and the best way to get around this massive problem in SIBO testing and diagnosis. 

The Gold Standard Test

The gold standard test used to diagnose SIBO is what is known as a small bowel aspirate and culture. The small bowel is sampled and then cultured. If the cultured microbes reach a certain threshold it is considered small intestinal overgrowth (22). 

A few issues have been raised around this invasive and costly procedure.

• Where the sample was taken in the small bowel (the bacterial overgrowth may have been missed).
• Sample handling and culturing techniques vary
• How much is considered an overgrowth? 
• Many bacteria sampled cannot be cultured 

These issues and more have led researchers and gut health clinicians to look for better alternatives in assessing someone for small intestinal bacterial overgrowth. 

Introducing the SIBO breath test with all of its pros and cons!   

Breath Testing

An overview of the concept of breath testing is shown in the image below. 

Sugar is consumed. If there is sufficient bacteria in the small intestines then they will ferment the sugar and produce hydrogen and/or methane and carbon dioxide. Excess hydrogen and methane gas makes their way into the bloodstream and out of the body via the lungs which is then captured and assessed.

A sufficient rise in either one or both, within a given time, would indicate SIBO.

If there is a significant rise beyond the given time this indicates that the sugar has passed through the small intestines and into the large bowel where it has been fermented by the bacteria there.

The North American Consensus on SIBO Breath Testing

In 2017 a paper was published in the American Journal of Gastroenterology outlining a panel of SIBO researchers consensus on SIBO breath testing. Did I mention it was complicated? The paper outlined a number of key points that you need to be aware of when considering which SIBO breath test is best and how to interpret it. 

Key points from the paper include the following 

1. Avoid antibiotics for at least 4 weeks prior to SIBO breath testing. 
2. Stopping prebiotics and probiotics was unclear – some say yes some were uncertain
3. Stopping promotility and laxative agents for 1 week prior to SIBO breath testing was recommended.
4. Avoiding fermentable foods (complex carbohydrates, FODMAPS etc) should be avoided for 1 day prior to SIBO breath testing.
5. Fasting for 8-12 hours before the SIBO breath testing was recommended.
6. Patients should avoid smoking and exercising before the SIBO breath test.   

Each SIBO breath testing provider will have their own approach and best practices for getting the most from the test. It is best to follow their recommendations (or the health clinician you are working with) to the letter. The worst scenario would be a user error which normally means you have to pay for another test.

Glucose

Glucose is a very well studied sugar used in SIBO breath testing. It is considered very specific but not very sensitive. 

When glucose is used as a breath testing sugar to diagnose SIBO there are very little chances of it saying you have SIBO when in fact you do not (only when the proper pre-test diet is followed as outlined above). However, there is a higher chance of a glucose breath test saying you do not have SIBO when in fact you do!

Here is why.  

Glucose is very easily absorbed in the upper small intestine. Why is that important? If the intestinal overgrowth is located further down in the small intestine (what is known as distal in medicine speak) then the glucose may not be available (as in it has already been absorbed into the bloodstream) to be fermented by the bacteria and produce a rise in gas levels as seen in the image below (44).

Positive Glucose Breath Test

For hydrogen dominant SIBO a rise of 20ppm of hydrogen over baseline in the first 90 minutes is thought to be a positive reading. This conclusion was drawn by the The North American Consensus paper on SIBO breath testing paper.

Methane dominant SIBO is less precise. The The North American Consensus paper on SIBO breath testing agreed that a level equal to or greater than 10ppm of methane was indicative of SIBO. Here there is the issue of methane production in the large bowel. Some clinicians would want to see a rise in methane of 10ppm or more within the first 90 minutes to help distinguish between large bowel methane production and methane dominant SIBO.

Pros of glucose breath testing

Glucose breath testing is highly specific. If there is a significant rise in gas production (and you have followed the proper test prep instructions) then SIBO is probable.

Cons of glucose breath testing

Glucose breath testing is not very sensitive. If there is no rise in gas production then you may still have SIBO.

Lactulose

Moving onto the darling sugar used in SIBO breath testing we come to lactulose. It has been getting a ton of press lately for reasons that I will outline below. 

First off what is lactulose?

Lactulose is a semi-synthetic disaccharide formed from lactose. It acts as a prebiotic, meaning it reaches the large intestine undigested and can be fermented and consumed by beneficial bacteria (45). 

When consumed as a sugar for a SIBO breath test lactulose makes its way through the small intestine and into the large intestine where it is fermented by colonic bacteria, resulting in the production of hydrogen and possibly methane (if methanogens are present). If there is an overgrowth of bacteria in the small intestine – if SIBO is present – then there will be a rise in hydrogen and/or methane before the lactulose reaches the colon (46).

There have been a range of different interpretations proposed for the interpretation of a positive lactulose breath test ranging from the ‘double peak’ – the thinking here is that the first peak signifies bacterial fermentation in the small bowel and the second peak signifies bacterial fermentation in the large bowel – and the ‘early rise’ – a rise in hydrogen above 20 ppm over baseline within 90 minutes – (both seen in the image below)

In the The North American Consensus paper on SIBO breath testing they agreed that the ‘early peak’ was a better indication of a SIBO positive patient and that the ‘double peak’ was not necessary for a positive result. 

Positive Lactulose Breath Testing

This is much the same as the glucose breath test taking into account the issues with lactulose breath testing outlined below.

For hydrogen dominant SIBO a rise of 20ppm of hydrogen over baseline in the first 90 minutes is thought to be a positive reading. This conclusion was drawn by the The North American Consensus paper on SIBO breath testing paper.

Methane dominant SIBO is less precise. The The North American Consensus paper on SIBO breath testing agreed that a level equal to or greater than 10ppm of methane was indicative of SIBO. Here there is the issue of methane production in the large bowel. Some clinicians would want to see a rise in methane of 10ppm or more within the first 90 minutes to help distinguish between large bowel methane production and methane dominant SIBO.

Issues with Lactulose breath testing

As with every other SIBO test available lactulose breath testing does have its own issues. 

First off we have patients with fast oral-cecal transit time. This is common in people suffering from diarrhea – a common SIBO symptom. Secondly lactulose is commonly used as a laxative and has been shown to speed up transit time! With a faster transit time an early rise in gas production could mean that the lactulose has reached the colon – here we could suffer from a false positive diagnosis of SIBO (22).

The last issue, and one that many clinicians miss, is the fact that lactulose is very selective in which bacteria it feeds. This is why it has commonly been used as a prebiotic. Certain bacteria cannot use lactulose as a food source. If these bugs were making up the small intestinal overgrowth there is a high chance of getting a false negative.  

Pros of lactulose SIBO breath testing.

It is a commonly used SIBO breath test sugar, is widely available and is relatively affordable

Cons of lactulose SIBO breath testing.

Lactulose SIBO breath testing may miss certain cases of SIBO due to the selectivity of the sugar. Using it may also result in false positives due to the increased transit time. 

Fructose

A third sugar, very rarely used in clinical and research settings to identify SIBO, is fructose. Commonly this sugar is used to identify fructose malabsorption issues. In a healthy small intestine fructose should at least partly be absorbed. When there is fructose malabsorption the sugar makes its way down to the large bowel where it can cause issues such as bloating, nausea and even diarrhoea. 

Fructose malabsorption is such a common issue that some researchers are even considering it as one of the issues causing irritable bowel syndrome (47).

The image below shows fructose malabsorption leading to excessive fructose reaching the colon and the classic symptoms of fructose malabsorption being produced. What is not shown in the image below, and what few gut health professionals are aware of, is the possibility of the malabsorbed fructose being fermented in the small intestine even before it reaches the large intestine. If there is an early rise of gases on a fructose SIBO breath test then, you guessed it, you could be dealing with SIBO. 

Pros of fructose SIBO breath testing.

Including the fructose SIBO breath test covers more area when testing for SIBO.

Often times SIBO patients have trouble absorbing fructose in the small intestine due to the damage done to the microvilli. If this is the case then the poorly absorbed fructose will be fermented in the small bowel and turn up as a positive SIBO breath test.

Cons of fructose SIBO breath testing.

Fructose is not a commonly used sugar for detecting SIBO.

There is very little research available and no consensus on proper interpretation guidelines. As such it is best used in combination with other breath tests (glucose or lactulose) 

Which Test is Best when Screening for SIBO?

And now the million dollar question. Which test is best for proper SIBO diagnosis? 

Seeing as each test, from the aspirate and culture to everyone of the three breath test sugars (glucose, lactulose and fructose) all have their issues and proper diagnosis of SIBO is so important before any microbiome restoration can happen in the large bowel we need to use a combination of tests to be sure. 

The best practice, as outlined by Dr Jason Hawrelak, one of the top gut health practitioners here in Australia, is to use multiple breath tests each with a different sugar. 

Screening for small intestinal bacterial overgrowth using glucose, fructose and lactulose (each on different days) makes up for each of the different sugars shortcomings. Plus noting which sugar is fermented in the small bowel and which isn’t can help when it comes to the treatment of SIBO.   

SIBO diets

The approaches to dietary interventions for SIBO vary depending on who you speak to. A few of the top diets for SIBO include the low FODMAP (stands for fermentable oligosaccharide, disaccharide, monosaccharide and polyol) diet, the SCD (specific carbohydrate) diet and the GAPS (gut and psychology syndrome) diet. 

Below is a short snapshot of the low FODMAP diet which is commonly used to minimise the symptoms associated with SIBO. 

Just a quick note here. 

I am including these dietary interventions here due to the fact that they are frequently recommended for SIBO patients by different clinicians. 

I wouldn’t personally endorse one over the other to (or any to be frank) for all SIBO patients. Again it comes down to the individual patient, how they are presenting and also which test was used to screen for SIBO.   

The low FODMAP diet

The low FODMAP diet is the most frequently diet used to manage symptoms associated with SIBO. 

First off what is a low FODMAP diet?

The quick answer here is that it is a very restrictive diet.

The low FODMAP diet restricts a whole range of carbohydrates that can be fermented by the bacteria that reside in your gastrointestinal tract including

• Fructose (particularly in excess of glucose)
• Oligosaccharides found in many foods including wheat and onions
• Galacto-oligosaccharides – found in legumes 
• Sugar polyols – sorbitol and mannitol 
• Lactose – particularly if it is poorly absorbed 

The idea around this diet stems from the idea of limiting poorly absorbed short-chain carbohydrates, thus limiting fermentation and gas production which is associated with symptoms of SIBO such as bloating and distention (49). 

It has been commonly prescribed for patients with IBS and has shown good success in reducing their symptoms (50).

Remember when we covered the connection between SIBO and IBS? Due to the overlap, many things that improve IBS symptoms may also improve SIBO symptoms. 

It is important to note that a low FODMAP diet is not a no FODMAP diet. The particular approach involved restricting these foods, noting whether symptoms have improved, then reintroducing different types of FODMAPs one at a time and finally customising your personal low FODMAP diet (51).

Risks with the low FODMAP diet

The low FODMAP diet does come with a few possible downsides as listed in a 2017 review paper Controversies and Recent Developments of the Low-FODMAP Diet

1. Using the low FODMAP diet to ‘diagnose’ IBS is used by some clinicians. This is considered poor practice and proper diagnostic procedures are much better suited. An example here would be using the ROME criteria for IBS and excluding other pathologies like SIBO, gluten sensitivities and large bowel dysbiosis. 
2. Disordered eating. As with many restrictive diets the low FODMAP diet can lead to eating disorders in certain predisposed people.
3. Altered gastrointestinal microbiota. This may be the top offender when it comes to issues with the low FODMAP diet. Many FODMAPs, due to their fermentable nature, have prebiotic like effects on the gut microbiota. Low FODMAP diets have been shown to reduce levels of beneficial bacteria in the large bowel. Other possible negatives of the low FODMAP on the gut microbiome include a reduction in the butyrate producing beneficial bacteria. 

Due to these issues it is best to limit the low FODMAP diet to the treatment phase and begin to reintroduce fermentable carbohydrates as quickly as possible. 

Conventional treatment for SIBO

Conventional treatment for SIBO is antibiotics. The thinking here is that if there is a bacterial overgrowth then the treatment is to remove the bacteria that are overgrowing. Pretty straight forward right?

Antibiotics in SIBO

Commonly used antibiotics include 

• Clindamycin
• Metronidazole
• Neomycin
• Rifaximin
• Tetracycline

Each of these different antibiotics have different success rates with successful interventions ranging from 35% up to 100% (53).

Rifaximin appears to be the antibiotic of choice for hydrogen dominant SIBO. The archaea involved in methane dominant SIBO (Methanobrevibacter smithii) appear to be more antibiotic resistant. When methane dominant SIBO is present the most common conventional approach appears to be a combination of both neomycin and rifaximin (54).

Pros of Rifaximin over other Antibiotics

As a herbalist and a microbiome explorer and admirer I am not a huge fan of antibiotics and their overuse. The rise of resistant microbes and the negative impact on the gut microbiota puts me off antibiotics unless absolutely necessary. More on that here.  

With that out of the way rifaximin appears to be safer than most other antibiotics. 

First off it is effective against both anaerobic and aerobic bacteria plus it is very poorly absorbed into circulation. Rifaximin seems to be well tolerated with few adverse events noted (55).

One in-vitro study even showed some prebiotic effects of rifaximin on the large bowel gut microbiota. An increase in Bifidobacteria and Faecalibacterium prausnitzii were observed in a colonic like simulation (56).

These prebiotic effects on the colonic gut microbiota have been seen in a number of other studies (shown in the table below). 

While it seems that rifaximin is better tolerated than most other antibiotics and that it does not appear to cause microbiome damage and disruption in the large bowel it does not treat the underlying cause in many patients who eventually relapse (8).

Prokinetic Drugs

Prokinetic pharmaceuticals are often used in conventional medicine to encourage healthy movement through the small bowel in SIBO patients post antibiotic treatment.

These mainly include one of three drugs although others may be used (54).

• Erythromycin
• Domperidone
• Prucalopride

Erythromycin is actually an antibiotic, and although it is only used in small amounts as a prokinetic drug, it is still worth knowing that it’s primary use is to kill bacteria. 

Natural Treatments for SIBO

Herbal antimicrobials 

Herbal medicine can be very effective in treating SIBO. 

In fact, one particular study compared the use of herbal antimicrobials against rifaximin (a popular antibiotic for SIBO). They found that the herbal antimicrobials were actually more effective at treating SIBO than the antibiotic (58).

The study does have a few inconsistencies, mainly the smaller than recommended dose for rifaximin as well as the timing of the intervention. Either way it does show that herbs can be used to successfully treat SIBO.

Different herbs that are commonly used include ones high in different active constituents including those high in 

• Berberine
• Tannins 
• Volatile oils

Berberine rich herbs include 

• Philodendron 
• Coptis chinensis 
• Goldenseal 
• Oregon grape root
• Barberry 

There may be an overemphasis on berberine at the moment when treating different gut infections and overgrowths. There has even been talk about berberine-resistance. 

Plants rich in polyphenols are often a suitable alternative to berberine rich herbs. Some of these herbs are also rich in volatile oils (a major win!).

These include among many many others

• Pomegranate husk 
• Propolis 
• Cloves 
• Oregano leaf (not oil as it may be too damaging to the gut ecosystem)

Finally volatile oils from selective herbs have been used in the treatment of SIBO. 

These include

• Oregano oil
• Thyme oil
• Clove oil 
• Peppermint oil 

There is some concern around the damage to the gut microbiota composition when using such strong herbal oils. Many of these oils can almost be seen as broad-spectrum as antibiotics. 

As a clinical herbalist I would only recommend taking the whole plant, often in tincture form, instead of the isolated plant oils. 

Here we are still getting the oils (although at lower concentrations) along with all of the other active constituents that would be missed by going the oil only route.

Herbs to avoid

Apart from the long term use of herbal oils and berberine rich herbs there is one other herb that should be absolutely avoided. 

Grapefruit seed extract, often used as a potent herbal antibiotic, has been shown again and again to be a contaminated product spiked chemicals like benzethonium chloride and triclosan.

Some preliminary (and unfortunately unpublished data) has shown that it has broad-spectrum and devastating effects on the gut microbiota, possibly as bad as broad spectrum antibiotics.

Tailored Herbs for Specific SIBO Types

When it comes down to it  you really need to know which type of SIBO you are treating. Then the herbal formula can be specifically tailored to treat the specific bacterial overgrowth. 

Just throwing herbs and supplements at SIBO generally won’t get you very far.

Best case scenario you may clear the overgrowth, worse case scenario you will be throwing money away and prolonging your healing journey. 

Herbs to Treat the Underlying Cause of SIBO

Specific herbal medicines can be used to treat the different underlying causes of SIBO. 

If the underlying cause for your specific case of SIBO was low stomach acid then bitter herbs can be used to increase stomach acid production and digestive flow. 

If poor gut motility was the underlying cause then prokinetic herbs such as ginger can be used.

The herbal formulation is very much dictated on each individual person’s needs.

Probiotics in SIBO

Here we are venturing into controversial territory.

Are probiotics helpful when treating SIBO? 

It very much comes down, once again, to the type of SIBO and the type of probiotic. 

Thanks to all the hard work that Dr. Jason Hawrelak has done in educating naturopaths on probiotics it seems clear that probiotic strains come are key here (61).

Some probiotics may be helpful in reducing methane dominant SIBO (Lactobacillus reuteri stands out here) and some may help to speed gut transit time.

Working with a healthcare provider that really and truly understands probiotics and their appropriate use is important here. They may be hard to find and in high demand but don’t let that stop you from looking! 

One study assessed a probiotic in the treatment of SIBO in patients with chronic liver disease. 

They found that the probiotic group, taking a product called Duolac Gold resulted in SIBO symptom alleviation in 24% of the treatment group (it wasn’t clear whether they retested)

The probiotic contained the following strains and was given at a dose of 2 capsules daily for 4 weeks.

• Bifidobacterium bifidum (KCTC 12199BP)
• Bifidobacterium lactis (KCTC 11904BP)
• Bifidobacterium longum (KCTC 12200BP)
• Lactobacillus acidophilus (KCTC 11906BP)
• Lactobacillus rhamnosus (KCTC 12202BP)
• Streptococcus thermophilus (KCTC 11870BP)

In another study probiotics were assessed for the treatment of SIBO in a Chinese group of patients with gastric or colorectal cancer. 

They found that taking a certain probiotic called Bifidobacterium triple viable capsule was effective in treating SIBO in 81% of the probiotic group. 

The major issues with this study includes 

1. The diagnostic testing issues to determine SIBO. They used a glucose breath test and a cutoff of only 12 ppm of hydrogen increase over baseline. Now it is considered 20 ppm
2. The authors did not describe what probiotics were Bifidobacterium triple viable capsule product so we don’t know what type were used! 

Just from these two studies it should be clear that probiotics are a possible treatment option for SIBO. Combining them with herbal antimicrobials may very well improve their effects. 

Prebiotics in SIBO 

Again very controversial territory. Prebiotics in SIBO?

The use of prebiotics in SIBO treatment is a hotly debated topic. Many clinicians would advise against prebiotics when treating SIBO. Afterall, the low FODMAP diet, which restricts prebiotics, can be helpful for improving SIBO symptoms. 

The real art and science of prebiotic prescribing for SIBO comes down to determining which specific bacteria are overgrown in the small intestine. Seeing as we don’t have the technology to determine this educated guesses can be made. The second crucial part of this is symptom improvement or worsening by the patient when certain prebiotics are introduced. 

Personal note here. 

I have found that fructo-oligosaccharides are generally not well tolerated in SIBO patients. Things like FOS and inulin are best avoided *personal opinion here* until after the SIBO has been cleared.

Other prebiotics seem to be better tolerated depending on the patient.

One study found that combining a prebiotic, in this case partially hydrolysed guar gum, with antibiotics significantly improved eradication rates compared to the antibiotic alone. 

The debate goes on between clinicians and researchers that believe that this is due to the prebiotic feeding up the bacteria so that they were happy and rapidly dividing (thus more exposed to the antibiotic treatment) and the other side who believe that this particular prebiotic helped to modulate and rebalance the small intestinal gut microbiota.

Other than that specific study there are very few papers available looking at prebiotics and SIBO. 

One fascinating paper (which we have covered here) outlined an interesting case study where a patient, suffering from long term IBS, was treated successfully with a prebiotic called lactulose.

Lactulose shouldn’t be used in certain SIBO cases, mainly the ones that have been diagnosed with a lactulose breath test. That makes perfect sense when you think it through. If a lactulose SIBO breath test has shown that there are bacteria in the small intestine that can utilise lactulose as a food source you wouldn’t want to be feeding them up.  

Elemental Diet

Finally the elemental diet is commonly used in difficult to treat SIBO cases. 

The elemental diet is a specifically formulated diet which is absorbed in the proximal small bowel. Basically the nutrients in this liquid diet are completely absorbed quickly before they can be used as food by the bacterial overgrowth. 

The success rate of the elemental diet is approximately 80% for a two week diet. At two weeks if the SIBO breath test is still positive an additional week of the elemental diet bumps the success rate up to about 85% (66).

The Issues with the Elemental diet 

1. Cost. The elemental diet can be quite costly. That said, you are eliminating your shopping bill for the time that you are on the elemental diet so that needs to be factored in.
2. Palatability. The elemental diet is reported to taste terrible for some people. 
3. Weight loss. It can be difficult to maintain weight on the elemental diet. 

The pros and cons of the elemental diet (67) needs to be weighed up for each SIBO patient.

Why Does My SIBO Keep Coming Back?

SIBO relapse is common. Very common. 

It may be the one issue that few clinicians know how to address when treating SIBO.

For some patients it may be next to impossible to address the relapse issue.

One paper found that SIBO recurrence was upwards of 40% in a 9 month follow up of successfully treated patients.

Another study found that in patients who had cleared SIBO with antibiotics it returned in 13% in 3 months, 28% in 6 months and 44% in 9 months (68).

Treating the SIBO overgrowth in the first place is straightforward enough for most cases. True there are very tough to treat cases but with proper diagnosis (is it hydrogen dominant SIBO, methane dominant SIBO or both?) and targeted therapy most SIBO cases can be successfully cleared. 

Preventing a relapse is another thing.  

Getting to the bottom of why you had SIBO in the first place is key to working towards prevention of relapse.  

Preventing SIBO recurrence 

Maintaining remission in treated SIBO patients means addressing the original issue that led to the overgrowth in the first place. 

Motility agents may be required long term to keep the flow through the intestines and prevent stasis, stagnation and an overgrowth of bacteria. 

Conventional approaches rely on prokinetic drugs. Alternative practitioners (naturopaths, herbalists) rely on prokinetic herbs.

One approach is to limit your food intake to windows of the day. The fasted state encourages the migrating motor complex in the intestinal tract to sweep through and keep things moving along. That is akin to the grumbling of your stomach when you are hungry. 

In the table below we can see the approach taken by modern medicine to treat the underlying cause of SIBO.

Work with a SIBO savvy gut clinician 

As you have now learned small intestinal bacterial overgrowth can be more complicated than simply treating the bacterial overgrowth in the small bowel. There are high rates of relapse and underlying causes that are often not addressed. 

If you suspect you have SIBO and would like to organise a consultation with us here at Byron Herbalist then head over to our appointments page to organise a suitable time.

We use targeted herbal medicine, prebiotics, probiotics and microbiome restoration techniques to address the bacterial overgrowth and ensure that the underlying causes for your SIBO have not been neglected.  

We covered a lot there! 

Now over to you.

Do you have any questions, comments or experiences to share on small intestinal bacterial overgrowth? 

Use the comment section below to share them.

References and Resources 

1. Small Intestinal Bacterial Overgrowth: A Primary Care Review  
2. The small intestine microbiota, nutritional modulation and relevance for health
3. Review article: small intestinal bacterial overgrowth – prevalence, clinical features, current and developing diagnostic tests, and treatment
4. Gas and the Microbiome
5. Methane Production During Lactulose Breath Test Is Associated with Gastrointestinal Disease Presentation
6. Measurement of Hydrogen Sulfide during Breath Testing Correlates to Patient Symptoms
7. Small Intestinal Fungal Overgrowth
8. Small intestinal bacterial overgrowth syndrome
9. Proton Pump Inhibitor Use and the Risk of Small Intestinal Bacterial Overgrowth: A Meta-analysis 
10. Meta-analysis: proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth.
11. Proton Pump Inhibitors: Review of Emerging Concerns
12. Intestinal Bacterial Overgrowth During Chronic Pancreatitis 
13. Association of gastric hypoacidity with opportunistic enteric infections in patients with AIDS.
14. Jejunal bacterial overgrowth and intestinal permeability in children with immunodeficiency syndromes
15. The Epidemiology and Clinical Manifestations of Autoimmunity in Selective IgA Deficiency
16. Selective IgA deficiency: Epidemiology, Pathogenesis, Clinical Phenotype, Diagnosis, Prognosis and Management
17. Small Intestinal Bacterial Overgrowth in Patients With Lower Gastrointestinal Symptoms and a History of Previous Abdominal Surgery
18. Interaction between rifaximin and dietary fibre in patients with diverticular disease
19. Assessment of small intestinal bacterial overgrowth in uncomplicated acute diverticulitis of the colon 
20. A Prospective Evaluation of Ileocecal Valve Dysfunction and Intestinal Motility Derangements in Small Intestinal Bacterial Overgrowth
21. Assessment of Anti-vinculin and Anti-cytolethal Distending Toxin B Antibodies in Subtypes of Irritable Bowel Syndrome
22. Breath Testing for Small Intestinal Bacterial Overgrowth: Maximizing Test Accuracy
23. Small intestinal bacterial overgrowth and intestinal permeability
24. Review article: the gut microbiome as a therapeutic target in the pathogenesis and treatment of chronic liver disease. 
25. Small intestinal bacterial overgrowth and nonalcoholic fatty liver disease: a systematic review and meta-analysis
26. Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance
27. Systematic review and meta‐analysis: the prevalence of small intestinal bacterial overgrowth in inflammatory bowel disease
28. Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and metaanalysis
29. Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome: Systematic Review and Meta-analysis
30. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy
31. Malabsorption, Orocecal Transit Time and Small Intestinal Bacterial Overgrowth in Type 2 Diabetic Patients: A Connection
32. Small intestinal bacterial overgrowth in rosacea: clinical effectiveness of its eradication.
33. Assessment of small intestinal bacterial overgrowth in uncomplicated acute diverticulitis of the colon
34. Dysmotility and ppi use are independent risk factors for small intestinal bacterial and/or fungal overgrowth
35. Diagnosis and Management of Small Intestinal Bacterial Overgrowth
36. Small Intestinal Bacterial Overgrowth: Roles of Antibiotics, Prebiotics, and Probiotics
37. Characteristics of gut microbiota in adult patients with type 1 and type 2 diabetes based on next‑generation sequencing of the 16S rRNA gene fragment
38. Culturing the human microbiota and culturomics
39. Functions of the Microbiota for the Physiology of Animal Metaorganisms 
40. Jejunal Flora of Patients with Small Intestinal Bacterial Overgrowth: DNA Sequencing Provides no Evidence for a Migration of Colonic Microbes
41. First Large Scale Study Defining the Characteristic Microbiome Signatures of Small Intestinal Bacterial Overgrowth (SIBO): Detailed Analysis from the Reimagine Study
42. Characterization of Proximal Small Intestinal Microbiota in Patients With Suspected Small Intestinal Bacterial Overgrowth: A Cross-Sectional Study
43. Breath Tests for Gastrointestinal Disease: The Real Deal or Just a Lot of Hot Air? Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus
44. Is It Useful to Administer Probiotics Together With Proton Pump Inhibitors in Children With Gastroesophageal Reflux?
45. Medical, nutritional and technological properties of lactulose. An update
46.  The diagnosis of small intestinal bacterial overgrowth: Two steps forward, one step backwards?
47. Is Fructose Malabsorption a Cause of Irritable Bowel Syndrome? 
48. Fructose malabsorption
49. Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta‑analysis
50. Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta‑analysis
51. The low FODMAP diet in the management of irritable bowel syndrome: an evidence-based review of FODMAP restriction, reintroduction and personalisation in clinical practice
52. Controversies and Recent Developments of the Low-FODMAP Diet
53. A Systematic Review of Diagnostic Tests for Small Intestinal Bacterial Overgrowth
54. How to Test and Treat Small Intestinal Bacterial Overgrowth: an Evidence-Based Approach
55. Rifaximin dose-finding study for the treatment of small intestinal bacterial overgrowth
56. Rifaximin modulates the colonic microbiota of patients with Crohn’s disease: an in vitro approach using a continuous culture colonic model system  
57. Eubiotic properties of rifaximin: Disruption of the traditional concepts in gut microbiota modulation
58. Herbal Therapy is Equivalent to Rifaximin for the Treatment of Small Intestinal Bacterial Overgrowth
59. Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract
60. Development and Validation of an HPLC/UV/MS Method for Simultaneous Determination of 18 Preservatives in Grapefruit Seed Extract
61. Probiotics: Choosing The Right One For Your Needs
62. Short-term probiotic therapy alleviates small intestinal bacterial overgrowth, but does not improve intestinal permeability in chronic liver disease
63. Effect of probiotics on small intestinal bacterial overgrowth in patients with gastric and colorectal cancer
64. Clinical trial: the combination of rifaximin with partially hydrolysed guar gum is more effective than rifaximin alone in eradicating small intestinal bacterial overgrowth
65. Culture-proven small intestinal bacterial overgrowth as a cause of irritable bowel syndrome: response to lactulose but not broadspectrum antibiotics
66. A 14-day elemental diet is highly effective in normalizing the lactulose breath test 
67. Diagnosis of small intestinal bacterial overgrowth in the clinical practice
68. Small intestinal bacterial overgrowth recurrence after antibiotic therapy