Exploring Specific Disorders Diagnosed Through Breath Testing

Breath Testing for SIBO, Lactose Intolerance, Fructose Malabsorption, and Sucrose Intolerance

Are you curious about using Hydrogen / Methane breath testing at your practice to diagnose specific disorders, including small intestinal bacterial overgrowth (SIBO), lactose intolerance, fructose malabsorption, sucrose intolerance, and sorbitol sensitivity? These gastrointestinal issues are often missed. Breath testing can change the course of the health of many of your patients.

Patients come in with chronic digestive complaints. After ruling out inflammatory bowel diseases (IBD) and other serious gastrointestinal issues, many patients receive the diagnosis of irritable bowel syndrome (IBS). However, many of these patients may be dealing with underlying SIBO, lactose intolerance, fructose malabsorption, sucrose intolerance, or sorbitol sensitivity.

⅓ of 40 million IBS diagnosis have SIBO or Lactose Intolerance

If they don’t receive the proper diagnosis, they may never receive the proper treatment either. This will mean suffering with chronic symptoms for years or even for life. Fortunately, breath testing is an accurate, affordable, and simple way to test for SIBO and other disorders of carbohydrate metabolism.

In an earlier article, you learned about some of the disorders we can test for through breath testing and some of the causes and risk factors of these issues. But we didn’t go into detail about these conditions.

As a quick recap, let’s talk about some of the more specific disorders in more detail. But before that, a quick recap on what breath testing is.

What Is Hydrogen / Methane Breath Testing?

Hydrogen-methane breath testing, or breath testing, is a simple diagnostic test to measure the hydrogen (HO2) levels in the breath the patient exhales. Breath testing is an innovative and accurate method to diagnose a list of gut health issues.

Some of the specific disorders you may diagnose at your practice through breath testing may include:

  • Lactose intolerance or malabsorption
  • Small intestinal bacterial overgrowth (SIBO) (including SIBO-testing for those with diabetes)
  • Fructose malabsorption
  • Sucrose intolerance

Specific Disorders Diagnosed Through Breath Testings

Let’s look at the main disorders you can diagnose through breath testing.


Small intestinal bacterial overgrowth (SIBO) is a very common gastrointestinal (GI) disorder. It is characterized by the overgrowth of bacteria in the small intestine causing mucosal inflammation and chronic symptoms (1). Symptoms of SIBO may include bloating, gas, abdominal discomfort or pain, diarrhea, weakness, and fatigue.

As written about in this article, SIBO is very common in people with chronic gastrointestinal issues who get diagnosed with irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). Yet, many of these patients never receive the certainty of a diagnosis of SIBO and end up silently suffering with chronic symptoms without an appropriate SIBO treatment protocol.

In a 2023 review published in the World Journal of Gastroenterology, 33.8% of patients with an IBS diagnosis had underlying SIBO (2). An earlier, 2020 meta-analysis published in the World Journal of Gastroenterology has found that 36.7% of patients with IBS also had SIBO. Patients with IBS were 2.6 – 8.3 times more likely to test for SIBO than the healthy control group without IBS (3).

Moreover, SIBO is common in those who haven’t been diagnosed with IBS as well. The exact prevalence of SIBO in the general population is unknown. However, according to a 2013 review published in Alimentary & Pharmaceutical Therapeutics, the prevalence of SIBO may be up to 20% in the overall population (4).

Many studies identify SIBO in IBD and other more serious GI disorders as well. A 2019 systematic review and meta-analysis published in Alimentary Pharmacology & Therapeutics has found that SIBO was 9.51 times higher in patients with Crohn’s disease and ulcerative colitis compared to the control group (5).

The harsh acid environment of the stomach kills most bacteria that are ingested. As a result, there is usually a very low bacterial account in the small intestine. However, in achlorhydria, the lack of acid production in the stomach, bacteria may pass into the small intestine and colonize there. This can happen during aging with medications such as anti-reflux medications. Probiotic therapy can sometimes introduce bacteria into a susceptible small intestine (6).

Conditions associated with intestinal hypo-motility, scarring, or previous bowel surgery may result in blind loop syndrome or other causes of stagnation in the GI tract (7, 8, 9). Such stagnation may permit bacteria to enter the small intestine from the colon. If we see an increase in bacterial count of over 100,000 bacteria per milliliter in these conditions, it meets the criteria of bacterial overgrowth (10).

If there is a bacterial overgrowth in the small intestine, it exposes the complex sugar and other soluble carbohydrates in the small intestine to bacterial fermentation instead of being hydrolyzed by enzymes and absorbed in the normally relatively sterile small intestine. This may lead to chronic symptoms similar to what we see in carbohydrate metabolism. SIBO may also increase the risk or co-occur with lactose intolerance and other carbohydrate malabsorption issues (11). It may also destroy some vitamins, interfering with the proper absorption of short-chain fatty acids. The bacteria will also compete with sugar and other nutrients that normally are absorbed in the small bowel, causing further issues (12).

These types of issues can cause serious digestive disturbances in the body. And while many of these gut issues can be treated effectively, it’s dependent on accurate diagnosis. Breath testing for SIBO is now easy to offer, affordable, and can provides results in just a few days as an at-home test for patients, enabling practitioners get beyond the simple but incomplete IBS diagnosis and helpful for accelerating patient recovery.

Testing for SIBO

Breath testing for SIBO with glucose or lactulose as a substrate is a great test for diagnosing SIBO (12, 13). However, it can still be a difficult diagnosis in some cases, given the many variables involved in nutrient metabolism. Patients with diabetes are usually given lactulose as a substrate instead of glucose to avoid high blood sugar peaks. However, this is somewhat less accurate and may have a highly laxative effect on healthy people.

Jejunal aspirate and culture is another option, often mentioned as a gold standard (14). However, it is far from perfect, given that only a certain percentage of the bacteria that are aspirated from the small intestine can be cultured, according to some studies up to 50%. Not to mention that it is a rather uncomfortable, invasive, and expensive procedure.

When you distill all this together, combine hydrogen and methane measurements, and compare to the gold standard of jejunal aspirate, glucose SIBO testing may be 65 to 75% sensitive only and about 85% specific on average. Lactulose SIBO testing is only 60 to 65% sensitive and only 50 to 70% specific. In other words, a lot of false positives are common with lactulose testing. Testing with glucose is less likely to overestimate the presence of SIBO, but can still generate false negatives.

SIBO testing overall is far from perfect, and it’s important to find the right test to ensure the most accurate testing possible based on current standards and scientific advancement. You will learn more about AllClear Healthcare breath testing for SIBO at the end of this article.

Treatment of SIBO

According to Treatment of SIBO depends on each individual case. It should always be recommended and monitored by a qualified provider. It usually consists of one or sometimes repeated courses of non-absorbable antibiotics, Rifaximin. This is generally followed by specific diets, such as a low FODMAP diet, as well as, supplementation and probiotics. According to a 2017 review published in the Journal of Gastroenterology, patients treated with probiotics had better results than the non-probiotic group (15).

In some cases, such as for motility issues, specific treatments are recommended. In certain situations, even surgery is necessary to eliminate blind loops that have previously been created by surgery or by some underlying disease.

Lactose Intolerance

Lactose intolerance is a condition in which the small intestine is unable to produce enough of the lactase enzyme to digest lactose (milk sugar). As a result, patients will experience digestive symptoms when consuming dairy products with lactose. According to the National Institute of Diabetes, Digestive, and Kidney Disease of the National Institute of Health (NIH), about 68% of the human population has a decreased ability to digest lactose properly (16). Lactose intolerance is especially common in certain ethnicities, including West African, Asian, Arab, Jewish, Greek, and Italian descent. It is rather uncommon in Northern Europe.

Lactose intolerance should not be confused with dairy allergy, which is an allergic reaction to milk protein, not lactose. Lactose is a milk sugar, present in all mammal milk types, including cow, sheep, and goat milk. In lactose intolerance, patients have a partial or complete inability to metabolize lactose. This happens because of a partial or complete lack of the enzyme lactase, which is necessary to split this sugar. As a result of the lack of lactase, the body is unable to break down and absorb lactose. This will lead to the sugar molecules ending up in the colon, causing GI symptoms similar to SIBO, including bloating, gas, nausea, loose stools, and abdominal cramps.

Practitioners commonly see lactose intolerance in patients who were diagnosed with IBS. Lactose intolerance is also commonly seen in Celiac disease, though, of course, it is not the cause of Celiac (17, 18). In some cases, it is possible to see lactose intolerance after bowel infections, diarrheal illnesses, or antibiotic therapy.

Testing for Lactose Intolerance

Historically, the breath test replaced a blood test, which was based on the absence of an increase in blood glucose level following lactose ingestion. However, this lactose blood test is not as reliable as the hydrogen breath test since it produces a greater proportion of false negative and false positive tests.

The accuracy of breath testing depends on the specific breath test. When using hydrogen breath testing alone without methane determination, false negative results are reported in five to 18% of all lactose malabsorption. Adding the methane testing reduces the number of false negatives and increases the sensitivity to over 90%. The specificity, so the risk of indirectly the risk of running into a false positive, is much better than a lot of the other breath tests. The specificity is over 95%, so the risk of false positives is quite low. AllClear Healthcare uses the more accurate Hydrogen / Methane breath testing.

You will learn more about AllClear Healthcare breath testing for lactose intolerance at the end of this article.

Treatment of Lactose Intolerance

Treatment of lactose intolerance consists of avoiding lactose-containing foods and supplementing the lactase enzyme with meals. If there are other co-occurring GI issues, such as SIBO, those need to be addressed as well. It is a fairly common problem.

Fructose Malabsorption

Fructose malabsorption happens when the cells of the intestine are unable to absorb fructose normally. This can lead to chronic symptoms, including abdominal pain, bloating, gas diarrhea, or constipation. It is triggered by consuming foods containing fructose. As you see, these symptoms are very similar to IBS, SIBO, lactose intolerance, and other carbohydrate metabolism disorders.

Fructose malabsorption is a fairly common problem we see in medical practices. A 2016 study published in Molecular and Cellular Pediatrics found that 58% of participants had absorption issues (19). It is a common underlying issue in patients with an IBS diagnosis or IBS-like symptoms. A 2018 study published in the Journal of Neurogastroenterology and Motility, has found that 45.7% of patients with IBS but without SIBO had fructose malabsorption issues (20).

Fructose malabsorption shouldn’t be confused with hereditary fructose intolerance, which is an inherited condition in which the liver enzyme that breaks up fructose in the bloodstream is deficient (21). Hereditary fructose intolerance, in rare cases, can be fatal, which is not true for fructose malabsorption. Most patients with hereditary fructose intolerance are infants or children, we rarely see it in adults.

Fructose is absorbed in the small intestine without the help of any digestive enzymes. Even in healthy people, only about 25 to 50 grams of fructose per sitting can be properly absorbed. This is the reason why some clinicians feel that fructose malabsorption is not really an issue. But there is a significant group of people whose capacity for absorption is actually significantly less.

Testing for Fructose Malabsorption

When symptoms and an abnormal breath test appear with consumption of 25 grams or less of fructose per sitting, fructose malabsorption can be diagnosed. Simultaneous ingestion of fructose and sorbitol seems to increase the malabsorption of fructose. Fructose that’s not been adequately absorbed is fermented by colonic bacteria, producing hydrogen methane, maybe hydrogen sulfide and carbon dioxide, as well as short-chain fatty acids. This abnormal increase in the gas concentrations is detectable with the Hydrogen / Methane breath test with fructose as a substrate.

There’s also evidence that fructose malabsorption can cause decreased tryptophan, folic acid, and zinc levels in the blood.

One has to be careful with the results of the fructose breath test because a negative result does not completely rule out that a trial of fructose restriction may help that patient. In other words, the sensitivity is not over 90%. A positive result demonstrates that the absorptive capacity for fructose in that individual is relatively low. When seeing a positive result, it is advisable to recommend a trial of fructose restriction. Being aware of false positives, such a trial may be prompted as well, especially when other test results don’t show evidence of another underlying gut health issue.

You will learn more about AllClear Healthcare breath testing for fructose malabsorption at the end of this article.

Treatment for Fructose Malabsorption

Restricting the dietary intake of free fructose and or fructans, which are longer sugars containing fructose, may provide symptom relief in a high proportion of patients with such a functional gut disorder.

Sucrose Intolerance

Sucrose intolerance is another common form of carbohydrate malabsorption. It is the result of sucrase-isomaltase deficiency. Sucrose intolerance, sucrose is also called SROs is a two-sugar chain, a disaccharide composed of glucose and fructose, which are bonded together. The general public knows about sucrose as sugar, beet sugar, cane sugar, and basically the sugar we eat every day (22).

The sucrase-isolate maltase enzyme is designed to break the bond between the glucose and the fructose molecules. Once this enzyme splitting into single molecule sugars has happened in the small intestine, they can then be absorbed directly into the blood. If there is a deficiency in this enzyme, it will result in sucrose intolerance and related symptoms. Symptoms resemble symptoms of IBS, SIBO, and other disorders of carbohydrate metabolism, including bloating, gas, diarrhea, and abdominal cramping (22).

A genetic form of enzyme deficiency, congenital sucrase-isomaltase deficiency, causing similar issues, is quite common in the indigenous population of Canada, Alaska, and Greenland, at 1 in 20 being affected (23). However, it is very rare in European descent at 1 in 5,000 people (23). Acquired sucrose intolerance is more common and is associated with IBS, SIBO, small intestinal diseases, and aging. It is a secondary sucrose intolerance.  A 2022 study published in Proceedings (Bayern University Medical Center) has found that 34.4% – 40% of people with gastrointestinal issues had sucrose intolerance (22).

Diagnosis of Sucrose Intolerance

There are specific tests used to diagnose this. The most accurate test is the enzyme activity determination, which requires a biopsy of the small intestine. Though this is a very accurate test, it is also expensive, invasive, and complicated.

Using a sucrose breath test may be a better option. It is easy to perform. It’s not invasive. And it’s affordable compared to a biopsy and other more invasive GI testing.

Sucrose breath testing is slightly less sensitive and specific than the enzyme activity test. A deficiency of this enzyme may result in malabsorption of the sucrose. This can then lead to potentially serious symptoms, including episodes of hypoglycemia, and low blood sugar. As a result, patients may experience dizziness, palpitations, anxiety, and even fainting. However, considering the ease and cost of breath testing, it may be a preferred option of diagnosis.

You will learn more about AllClear Healthcare breath testing for sucrose intolerance at the end of this article.

Treatment of Sucrose Intolerance

Sucrase ISO maltase is also involved in the digestion of starches This means that some patients with sucrose intolerance may not be able to absorb starches very well. It’s important for patients with this disorder to minimize sucrose consumption as much as possible. There are enzyme supplements available as a substitute, which may be really helpful in the therapy.

Why Choose AllClear Healthcare Labs for Hydrogen Methane Breath Testing

SIBO and other disorders of carbohydrate metabolism are common issues in a significant enough percentage of the population to make it worthwhile to roll out accessible testing for everyone. If you are looking to use breath testing at your practice, we recommend AllClear Healthcare.

AllClear Healthcare is a CLIA-certified lab based in Massachusetts. At AllClear Healthcare, they offer FDA-approved and CLIA-waived testing for a variety of illnesses, including SIBO, lactose intolerance, fructose malabsorption, and sucrose intolerance. This means that they are obliged to maintain strict disciplines.

All of their technicians are trained on the analyzers before they start testing. They test the analyzers regularly for accuracy and with every new lot of test reagents. They also participate in internal and external quality controls.

All the breath tests are reviewed by Dr. Martin Hahn, Chief Medical Officer and Medical Advisor at AllClear Healthcare and a physician with over 35 years of experience in clinical practice, internal medicine, and gastroenterology, as well as significant experience in laboratory and clinical research.

AllClear Healthcare strives to offer affordable, accurate, and rapid testing accessible to everyone, without delays.

Final Thoughts

Hydrogen/Methane Breath testing is currently the best way to diagnose small bacterial overgrowth (SIBO), lactose intolerance, fructose malabsorption, or sucrose intolerance in your patients. We recommend that you choose AllClear Healthcare Hydrogen/Methane Breath testing. It is the most accurate, non-invasive, easy-to-use, and affordable test option available today. It’s simple to use for your patients with straightforward results that can help you, as a practitioner, offer best-in-class diagnosis and the most effective treatment possible. Order your AllClear Healthcare breath test kits here today.

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