Author: Bradley Bush

Common Breath Test Results Part 3: Atypical Breath Test Results

Posted on by Bradley Bush

Atypical breath test patterns provide unique insights into digestive health and treatment direction. Consequently, interpret results within the clinical context. In general, despite expert and research-based guidelines for diagnostic breath testing, the interpretation of results lacks a clear, universally accepted consensus. This leaves room for broad, sometimes varied clinical interpretation, making results more functional and insightful. As hydrogen and methane breath test markers signal different underlying conditions based on timing, peak patterns, and gas fluctuations, clinicians rely on experience and understanding of individual patient patterns.

Atypical Breath Testing Patterns

Breath tests are essential for diagnosing digestive issues such as small/large intestinal bacterial overgrowth (SIBO and LIBO). However, some results fall into atypical patterns, giving unique insights. Here’s an overview of six atypical breath test result patterns.

Flat Methane

In this case of atypical breath results, methane (CH₄) levels are elevated, but flat, throughout the small intestine (0–120 min) (Figure 1). Elevated methane gas levels throughout test results suggest increased bacterial activity throughout the intestines or elevated colonic activity combined with reduced gut motility.

Test results showing an atypical breath test pattern: elevated flat methane
Figure 1: This is a lactulose breath test example of an atypical breath test result for a flat-line, elevated methane SIBO positive results.

Baseline Elevated Hydrogen

Initially high hydrogen (H₂) that either dips or remains high across the small intestine reflects potential pre-existing fermentation (Figures 2a, 2b). 

Atypical breath test results showing elevated baseline hydrogen
Figure 2a: This is an example of an elevated baseline hydrogen breath test. Elevated baseline (34 ppm) gas activity quickly cleared out with a significant reduction in activity. Possible causes of elevated hydrogen baselines include, but are not limited to, not following preparation diet guidelines, reduced gut motility, oral microbial imbalance, or significant colon gas activity.

 

Atypical breath test pattern showing baseline elevated hydrogen
Figure 2b: This is an example of an elevated baseline hydrogen breath test. An elevated baseline (34 ppm), followed by continued elevation in hydrogen gas activity does not meet diagnostic criteria for SIBO. Possible causes of continually elevated hydrogen gas activity include, but are not limited to, reduced gut motility, sugar malabsorption syndrome, and/or yeast overgrowth.

Flat Negative

Low hydrogen and methane (<3ppm) suggest low fermentative activity or microbial population (Figure 3).

atypical pattern for breath test showing flat methane and hydrogen levels in a negative SIBO result
Figure 3: This lactulose breath test result shows little to no measurable gas activity (hydrogen and methane). Common causes for a “flat-line” result include: testing too soon after antimicrobials (antibiotics, anti-fungals, herbal antimicrobials) or the presence of dominant hydrogen sulfide (H2S) SIBO.

Delayed Gut Motility

A hydrogen spike after 120 min with a second increase (double peak) shows slowed motility (Figure 4). Normally, a classic looking “double peak” of gas activity shows an initial spike in gas activity just prior to and after the intestinal transition zone (commonly around 100-120 min). The pattern becomes atypical when the double peak occurs outside of that time frame.

results showing delayed gut motility which is an atypical breath test pattern
Figure 4: These results show delayed emptying of lactulose from the small to large intestines. Reduced gut motility and delayed emptying may be identified with a transition zone occurring in the 140-160 minutes specimens.

Multiple Peaks and Valleys

Fluctuating H₂/CH₄ peaks may result from uneven microbial distribution (Figure 5).  Causes include segmental delays in motility, uneven transit times with pockets of microbes at different points, and SIBO. Additionally, different bacterial species producing gas at varying rates can fluctuate gas levels. Finally, physiological gut responses with normal motility patterns or minor motility disorders may influence gas patterns in the intestines.

multiple peaks and valleys in hydrogen methane breath tests are atypical
Figure 5: Multiple peaks and valleys in gas activity may be due to a variety of conditions.

Atypical Colon

A notable hydrogen and/or methane spike in the colon indicates possible microbial imbalance in the large intestines (Figures 6a, 6b).

Atypical colon breath test result
Figure 6a: This is atypical breath test example shows a slightly elevated SIBO (combined H₂ & CH₄) result with significant colon gas activity at 140-180 minutes. Additionally, the total hydrogen activity (Total Bacterial Load) of these results strongly suggests irregular colon fermentation/ microbial activity.

 

Atypical colon total bacterial load breath test results
Figure 6b: These breath test results show the total hydrogen gas activity (Total Bacterial Load) for the results in Figure 6a. Note high colon activity at 140-180 min.

Conclusion

Each atypical breath test pattern reveals distinct physiological and microbial dynamics. By combining the results with the clinical presentation, healthcare providers can create highly targeted and personalized treatment plans for various GI concerns. In some cases, these trends can be difficult to interpret. Neurovanna offers healthcare providers using our breath tests free consults with our SIBO expert Dr. Bradley Bush. Become a Neurovanna healthcare provider for quality and exclusive test results as well as skilled clinical support.

This is part 3 of a three part series on common breath test trends. Read part 1 to learn about common trends for lactulose and glucose SIBO breath tests. Part 2 discusses common trends in fructose, sucrose, and lactose sugar malabsorption breath test results.

Common Breath Test Results Part 2: Sugar Malabsorption Testing for Lactose, Fructose, and Sucrose 

Posted on by Bradley Bush

Sugar malabsorption affects many individuals, causing symptoms like bloating, gas, diarrhea, and abdominal discomfort. When the body cannot properly absorb sugars such as lactose, fructose, or sucrose, they pass into the large intestine. Once in the large intestine, gut bacteria fermented the sugars producing hydrogen and/or methane gas. Measuring the levels of hydrogen and methane gas through breath tests provides important insights into how well the body is digesting these sugars.

How Sugar Malabsorption Breath Tests Work

During a sugar malabsorption breath test, the patient consumes a specific sugar (either lactose, fructose, or sucrose). If the sugar is not properly absorbed in the small intestine, it reaches the colon. In the colon, bacteria ferment it producing hydrogen (H₂) and methane (CH₄) gas. Then, hydrogen gas absorbs into the bloodstream which carries it to the lungs. When the patient exhales into the collection tube, the gas is collected and measured using gas chromatography.

By analyzing the rise in hydrogen gas levels during the breath test, clinicians determine whether malabsorption is occurring and to what extent. The greater the rise in hydrogen, the more significant the sugar malabsorption.

Diagnostic Criteria for Sugar Malabsorption

The following diagnostic thresholds are used to interpret malabsorption breath tests for lactose, fructose, and sucrose:

  1. Hydrogen: A rise > 20 ppm above baseline during the breath test is diagnostic of malabsorption.
  2. Combined Hydrogen and Methane: A rise > 15 ppm above baseline during the breath test is diagnostic of malabsorption 
  3. Methane: A rise > 12 ppm above baseline during the breath test is diagnostic of malabsorption.

Common Trends for Each Sugar Malabsorption Test

Lactose Malabsorption (see Figure 1)

  • Hydrogen Gas Trend: For individuals with lactose intolerance, a significant rise in hydrogen levels commonly occurs within 60 to 90 minutes after ingesting lactose.
  • Diagnostic Interpretation:
    • A rise of 20 ppm or more indicates severe lactose malabsorption where the the small intestine absorbs little to no lactose.
    • An increase of 15 ppm or more indicates moderate malabsorption suggesting partial lactase deficiency.
    • A rise of 12 ppm or more indicates mild malabsorption. In this case, some lactose is absorbed, but not enough to prevent symptoms like gas and bloating.
  • Symptoms: Common symptoms include bloating, diarrhea, and abdominal pain after consuming dairy products.
Sugar malabsorption breath test results showing a negative results for lactose malabsorption
Figure 1: Example of lactose malabsorption breath test report. This breath test did not meet diagnostic criteria for malabsorption.

Fructose Sugar Malabsorption (see Figure 2)

  • Hydrogen Gas Trend: In cases of fructose malabsorption, hydrogen levels typically rise 30 to 60 minutes after consuming fructose.
  • Diagnostic Interpretation:
    • A rise of 20 ppm or more indicates severe fructose malabsorption, often causing significant digestive distress.
    • An increase of 15 ppm or more indicates moderate malabsorption, with symptoms occurring after consuming high amounts of fructose.
    • A rise of 12 ppm or more indicates mild malabsorption, where smaller quantities of fructose may still cause discomfort.
  • Symptoms: Fructose malabsorption can lead to bloating, gas, diarrhea, and cramping after consuming fructose-rich foods like apples, honey, or high-fructose corn syrup.
Test result showing positive fructose sugar malabsoprtion based on a breath test
Figure 2: Example of fructose malabsorption breath test report. Baseline measurement showed very little gas activity and then a significant increase was seen at 120 minutes. This breath test met diagnostic criteria for both an increase in hydrogen and combined (hydrogen + methane) gases.

Sucrose Malabsorption (see Figure 3)

  • Hydrogen Gas Trend: For those with sucrose malabsorption, hydrogen levels typically  rise 30 to 60 minutes after ingesting sucrose.
  • Diagnostic Interpretation:
    • A rise of 20 ppm or more suggests severe sucrose malabsorption, indicating a deficiency in the enzyme sucrase.
    • An increase of 15 ppm or more indicates moderate malabsorption, with symptoms occurring after consuming moderate amounts of sucrose.
    • A rise of 12 ppm or more indicates mild malabsorption, where some sucrose is absorbed, but not enough to prevent symptoms like bloating and gas.
  • Symptoms: People with sucrose malabsorption often experience digestive discomfort after consuming sugary foods like candy, baked goods, and sweetened beverages.
Breath test report showing positive for sucrose sugar malabsoprtion
Figure 3: Example of sucrose malabsorption breath test report. Even with an elevated baseline, this patient met diagnostic criteria for both an increase in hydrogen and combined (hydrogen + methane) gases.

What Do These Trends Mean?

The trends in hydrogen gas production during sugar malabsorption breath tests provide valuable insight into how well the body is absorbing specific sugars. A sharp increase in hydrogen levels, especially within the first 90 minutes, indicates a significant amount of undigested sugar is reaching the colon, where it is fermented by bacteria. The higher the hydrogen gas levels, the more severe the sugar malabsorption.

Understanding these hydrogen gas trends helps clinicians tailor dietary recommendations and treatment plans for individuals struggling with lactose, fructose, or sucrose malabsorption. For patients experiencing significant rises in hydrogen gas levels, reducing or eliminating the offending sugar from the diet can help manage symptoms and improve digestive health.

Prevent False Positives: Rule Out SIBO Before Sugar Malabsorption Breath Testing

SIBO can interfere with the accuracy of sugar malabsorption test results. Therefore, the North American Consensus for Breath Testing recommends ruling out Small Intestinal Bacterial Overgrowth (SIBO) with a glucose or lactulose breath test before testing for sugar malabsorption (such as lactose, fructose, or sucrose). If SIBO is present, bacteria in the small intestine may ferment sugars prematurely causing false positives during sugar malabsorption testing. By addressing SIBO first, clinicians can ensure that any malabsorption detected is due to enzyme deficiencies or transport issues rather than bacterial overgrowth.

This is part 2 of a three part series on common breath test trends. Read part 1 to learn about common trends for lactulose and glucose SIBO breath tests.

Common Breath Test Results Part 1: SIBO

Posted on by Bradley Bush

SIBO (small intestinal bacterial overgrowth) breath testing measures the production of hydrogen and methane gases by bacteria in the gut. These breath test results offer important insights into bacterial overgrowth.  First, individuals ingest glucose or lactulose, which are fermented by bacteria in the small intestine. By assessing the changes in gas production during the breath test, SIBO can be diagnosed. This article is part one of a three-part series discussing common trends and diagnostic criteria for both glucose and lactulose breath testing.

Glucose Breath Test Results

Glucose is absorbed in the small intestine relatively quickly, making it an excellent substrate for detecting bacterial overgrowth in the upper part of the small intestine.

Positive Glucose SIBO Breath Test Results (Hydrogen or Methane Elevation within 120 minutes)

  • Hydrogen Rise: An increase in hydrogen gas of 12 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 1). This indicates that bacteria in the small intestine are fermenting glucose before it can be fully absorbed.

    Graph showing positive SIBO results
    Figure 1: Hydrogen Rise: An increase in hydrogen gas. Glucose is mostly absorbed in the small intestines therefore the increase in gas is from bacteria.
  • Peak Methane Levels: A peak methane level of 10 ppm or more within 120 minutes suggests the presence of methane-producing bacteria in the small intestine, meeting the criteria for SIBO (Figures 2 & 3). Methane-producing bacteria are often associated with constipation.
    Graph showing increasing levels of methane on SIBO test
    Figure 2 Peak Methane Level: Methane gas activity achieves a level of more than 10 ppm from 60-180 minutes of the test. This indicates the presence of methane producing bacteria and SIBO.Graph showing elevated methane levels on a SIBO test

    Figure 3 Peak Methane Level: Methane gas activity elevated throughout test (baseline to 180 minutes).

  • Combined Hydrogen + Methane Rise: An increase in the combined total of hydrogen and methane gas of 12 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 4). This indicates bacteria in the small intestine ferment the glucose before it can be fully absorbed.
    Graph showing positive SIBO results based on combined gas levels
    Figure 4 Combined Hydrogen + Methane Rise: A rise in the combined total of hydrogen and methane gas of 12 ppm (glucose)/ 15 ppm (lactulose) or more within the first 120 minutes meets the diagnostic criteria for SIBO. This is an example of a positive glucose breath test result.

     

Negative Glucose SIBO Breath Test Results

In healthy individuals, glucose absorbs before it reaches the large intestine, and there is no significant rise in hydrogen or methane within the first 120 minutes (Figure 5). Gas production occurring after 120 minutes reflects normal fermentation in the large intestine.

graph showing negative SIBO test
Figure 5 Negative SIBO: No significant increases in hydrogen gas, methane levels below 10 ppm, and insignificant levels of combined gases indicates negative breath test results.

 

Lactulose Breath Test Results 

Lactulose is not absorbed by the body and passes through both the small and large intestines, making it useful for detecting bacterial overgrowth in both regions. 

Lactulose Positive SIBO Breath Test Results (Early Hydrogen or Methane Rise within 120 minutes)

  • Hydrogen Rise: A hydrogen increase of 20 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO, indicating fermentation in the small intestine by bacteria (Figure 6).graph showing a positive lactulose breath test resultsFigure 6 Hydrogen Rise: An increase in hydrogen gas. Lactulose is not absorbed in the intestines. Therefore, large intestinal bacterial fermentation is observed (typically 140-180 minutes).
  • Peak Methane Levels: A peak methane level of 10 ppm or more within 120 minutes suggests the presence of methane-producing bacteria in the small intestine. This meets the criteria for SIBO (Figures 2 & 3). Methane-producing bacteria are often associated with constipation.
  • Combined Hydrogen + Methane Rise: An increase in the combined total of hydrogen and methane gas of 15 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 4). This indicates bacteria in the small intestine ferment lactulose. 

Lactulose Negative SIBO Breath Test Results

In a negative test, there will be no significant gas rise in the first 120 minutes. Additionally, gas production typically rises after this period, reflecting normal lactulose  fermentation within the large intestine (Figure 5).

Common Trends in Hydrogen and Methane Gas Production

  • Hydrogen-Dominant SIBO: Patients with diarrhea-predominant symptoms (IBS-D) often show elevated hydrogen levels. A sharp rise in hydrogen gas, particularly early in the breath test, suggests bacterial fermentation of glucose or lactulose in the small intestine. (Figures 1 & 6)
  • Methane-Dominant SIBO: Patients with constipation-predominant symptoms (IBS-C) usually present with elevated methane levels. High methane gas, especially when peaking at 10 ppm or more within 120 minutes, indicates the presence of methanogenic archaea. The presence of these bacteria can slow intestinal transit. (Figures 2 & 3)
  • Mixed Hydrogen and Methane Production: Some patients may show elevated levels of both hydrogen and methane gases, leading to a mix of symptoms such as alternating diarrhea and constipation. This pattern can indicate the presence of both bacterial overgrowth and methanogens in the small intestine. (Figure 4)
  • Double Peak Patterns:  For lactulose, a double peak may be observed. If SIBO is present, the first peak occurs within 120 minutes due to small intestinal fermentation. As lactulose reaches the colon, fermentation by colonic bacteria cause the second peak (Figure 7). Double peak results used to be diagnostic for SIBO but are not anymore due to improvements in testing methodology. However, double peaks seen on testing can assist in differentiating between small and large intestine specimen assessments. 

    graph showing a double peak in a lactulose breath test result
    Figure 7: Classic double peak observed during a lactulose breath test. Two distinct rises in gas levels during the breath test are observed. The first peak occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as lactulose reaches the colon where colonic bacteria begin their fermentation process.

Conclusion

Both glucose and lactulose are good substrates for SIBO breath testing. For glucose breath tests, a rise in hydrogen levels or combined gases of 12 ppm or more within 120 minutes meets the criteria for diagnosing SIBO. For lactulose breath tests, hydrogen levels rising by 20 ppm or more or 15 ppm (combined gases) within 120 minutes also indicate SIBO. Peak methane levels of 10 ppm or more indicate methane-dominant SIBO. These tests help clinicians distinguish between hydrogen-dominant and methane-dominant SIBO, leading to more targeted treatment plans.

This is the first blog in a three-part series. Part 2 discusses fructose, lactose, and sucrose sugar malabsorption patterns. In part 3, learn about atypical breath test patterns.

The Case for Large Intestine Bacterial Overgrowth (LIBO)

Posted on by Bradley Bush

Breath testing is commonly used to diagnose Small Intestinal Bacterial Overgrowth (SIBO), but it could also be used to identify Large Intestine Bacterial Overgrowth (LIBO). The SIBO breath test measures amounts of the gasses hydrogen and methane produced by bacteria in the small intestine when they ferment carbohydrates. However, these breath tests also assess the hydrogen and methane gas activity in the large intestines. In most cases, this data is ignored, but this oversight may prevent proper diagnosis and treatment.

SIBO vs LIBO

In a healthy digestive system, the small intestine has relatively few bacteria compared to the large intestine. However, in SIBO, an overgrowth of bacteria in the small intestine ferments carbohydrates prematurely. This fermentation produces gasses, primarily hydrogen, methane, or hydrogen sulfide, which are absorbed into the bloodstream and then exhaled through the lungs. After a patient ingests a specific carbohydrate substrate, like lactulose or glucose, the breath test detects the levels of these gasses. Abnormally high levels indicate bacterial overgrowth in the small intestine.

The large intestine, or colon, is naturally populated with a vast number of bacteria responsible for fermenting undigested carbohydrates. This fermentation produces gasses like hydrogen, methane, and carbon dioxide as a normal part of digestion. Because this process is a normal function of the large intestine, the conventional medical community believes that assessing gas activity of the colon has no diagnostic value. In other words, elevated gas levels detected later in the breath test are expected, to some degree, and therefore do not specifically indicate pathology.

Large Intestinal Bacterial Overgrowth (LIBO) is a condition where there is an abnormal increase in the number and/or types of bacteria in the large intestine (colon). While the colon normally contains a vast and diverse population of bacteria that play essential roles in digestion, immunity, and overall health, an imbalance or overgrowth of certain bacterial species can lead to digestive issues and other health problems.

Key Aspects of Large Intestinal Bacterial Overgrowth (LIBO)

Causes of LIBO

  • Dietary Factors: A diet high in refined carbohydrates or sugars and low in fiber can promote bacterial overgrowth in the large intestine.
  • Dysbiosis: An imbalance in the gut microbiota, often caused by factors like antibiotics, poor diet, chronic stress, or other medications, can lead to LIBO.
  • Slow Transit Time: Conditions that slow down the movement of food through the colon, such as constipation, can lead to bacterial overgrowth as bacteria have more time to ferment undigested food.
  • Immune System Dysfunction: A weakened immune system, which fails to keep bacterial populations in check, can contribute to LIBO.

Symptoms of LIBO

  • Abdominal Bloating and Gas: Excess fermentation of undigested carbohydrates by bacteria can produce large amounts of gas, leading to bloating and discomfort.
  • Diarrhea or Constipation: LIBO can cause changes in bowel habits, leading to either diarrhea (due to rapid fermentation and irritation) or constipation (due to slower transit and hard stools).
  • Abdominal Pain: The buildup of gas and changes in motility can cause cramping and discomfort in the abdomen.
  • Fatigue and Malaise: Chronic LIBO can lead to malabsorption of nutrients, resulting in fatigue, nutrient deficiencies, and general feelings of unwellness.

Hydrogen Gas Production in the Large Intestine

The large intestine is home to a vast and diverse community of bacteria, many of which play a key role in digesting food components that were not fully broken down in the small intestine. These bacteria ferment undigested carbohydrates, fibers, and other nutrients, producing gasses as byproducts. Hydrogen gas (H₂) is one of the primary gasses produced during this fermentation process.

When carbohydrates, especially complex carbohydrates and fibers, reach the large intestine, they become substrates for bacterial fermentation. The bacteria break down these carbohydrates to obtain energy, and in the process, hydrogen gas is released along with other gasses like carbon dioxide (CO₂) and methane (CH₄).

Fate of Hydrogen Gas in the Large Intestine

  • Hydrogen-Consuming Microbes: In a healthy gut, hydrogen gas produced by one group of bacteria is often consumed by other microbes. For example:
      • Methanogenic Archaea: These microbes convert hydrogen gas into methane, which is another gas commonly found in the colon.
      • Sulfate-Reducing Bacteria: These bacteria use hydrogen to reduce sulfate to hydrogen sulfide (H₂S).
      • Acetogens: These microbes can convert hydrogen gas into acetate, which is a short-chain fatty acid beneficial for gut health.
  • Exhalation and Flatulence: Some of the hydrogen gas is absorbed into the bloodstream and then exhaled through the lungs, which is why hydrogen breath tests are used to diagnose certain gastrointestinal conditions. The remaining hydrogen gas, along with other gasses produced in the colon, can be expelled as flatulence.

Conditions Influencing Hydrogen Production in the Large Intestine

  • Dietary Composition: Diets high in fermentable fibers, sugars, and complex carbohydrates can increase hydrogen gas production in the large intestine because they provide more material for bacterial fermentation.
  • Gut Microbiome Balance: The balance of different types of bacteria in the large intestine influences hydrogen production. A healthy balance means that hydrogen production and consumption are balanced, minimizing excess gas.
  • Digestive Disorders: Conditions like irritable bowel syndrome (IBS), small intestinal bacterial overgrowth (SIBO), or malabsorption syndromes can lead to increased hydrogen production, contributing to symptoms like bloating, discomfort, and gas.

Summary

Hydrogen gas is indeed produced in the large intestine as a result of bacterial fermentation of undigested carbohydrates and fibers. The gas is either consumed by other gut microbes, absorbed into the bloodstream and exhaled, or expelled as flatulence. The production of hydrogen gas in the colon is a normal part of digestion, but excessive production may contribute to digestive discomfort, bloating, excessive flatus, irritable bowel symptoms and may suggest the presence of LIBO. Total hydrogen activity assessed during breath tests, e.g. the Neurovanna Total SIBO Bacterial Load, offer another functional diagnostic tool for assessing the presence and extent of LIBO. 

Start testing with Neurovanna or contact us for more information.

Learn more about the author, Dr. Bradley Bush.

A Review of Breath Testing

Posted on by Bradley Bush

Small Intestinal Bacterial Overgrowth (SIBO) is a condition characterized by an excessive growth of bacteria in the small intestine. Diagnosing SIBO accurately is crucial for effective treatment, and one of the primary diagnostic tools is breath testing. Breath tests typically use either lactulose or glucose as substrates.

Breath Testing for SIBO Breath testing measures the amount of hydrogen and methane gasses produced by bacteria in the small intestine. These gasses are not produced in significant quantities by human cells but are byproducts of bacterial metabolism. The presence and levels of these gasses in the breath can indicate bacterial overgrowth.

Types of Breath Tests

  1. Lactulose Breath Test (LBT)
  2. Glucose Breath Test (GBT)

Lactulose Breath Test (LBT) Lactulose is a non-absorbable sugar that passes through the small intestine into the colon. When lactulose is fermented by bacteria in the small intestine, it produces hydrogen and methane, which are absorbed into the bloodstream and exhaled in the breath.

Procedure

  1. Preparation: Patients fast for at least 12 hours before the test.
  2. Baseline Breath Sample: A baseline breath sample is collected to measure hydrogen and methane levels.
  3. Ingestion: The patient drinks a lactulose solution.
  4. Sampling: Breath samples are collected at regular intervals (usually every 15-20 minutes) for about 2-3 hours.

Interpretation There are a variety of published diagnostic criteria for lactulose breath tests. These are the most clinically relevant SIBO diagnostic criteria:

  • A rise over lowest preceding value in hydrogen production of 20 parts per million (ppm) or greater within 120 minutes after ingesting lactulose
  • A rise over lowest preceding value in methane production of 10 ppm or greater within 120 minutes after ingesting lactulose
  • A rise over lowest preceding value in the combined sum of hydrogen and methane production of 15 ppm or greater within 120 minutes after ingesting lactulose.

Advantage

  • Can detect overgrowth throughout the entire small intestine.

Disadvantage

  • Potential for false positives due to rapid transit time or colonic fermentation are possible, but most experienced practitioners can reduce false positives by combining clinical presentation with the tests results.

Glucose Breath Test (GBT) Glucose is a sugar that is absorbed in the proximal small intestine (the first part of the small intestine). If bacteria are present in this region, they will ferment glucose, producing hydrogen and methane.

Procedure

  1. Preparation: Similar to the lactulose breath test, patients fast before the test.
  2. Baseline Breath Sample: A baseline breath sample is collected.
  3. Ingestion: The patient drinks a glucose solution.
  4. Sampling: Breath samples are collected at regular intervals for up to 2-3 hours.

Interpretation There are a variety of published diagnostic criteria for glucose breath tests. Below are the most clinically relevant SIBO diagnostic criteria:

  • A rise over lowest preceding value in hydrogen production of 12 parts per million (ppm) or greater within 120 minutes after ingesting glucose.
  • A rise over lowest preceding value in methane production of 10 ppm or greater within 120 minutes after ingesting glucose.
  • A rise over lowest preceding value in the combined sum of hydrogen and methane production of 12 ppm or greater within 120 minutes after ingesting glucose.

Advantages

  • Higher published specificity and lower false positive rate compared to lactulose, although this is less of an issue with an experienced practitioner.
  • Less likely to be influenced by colonic bacteria since glucose is usually absorbed before reaching the colon.

Disadvantages

  • May miss bacterial overgrowth in the distal (farther) parts of the small intestine.
  • Does not provide additional information on colonic bacterial activity.

Comparison of Lactulose and Glucose Breath Tests

Lactulose Breath Test

  • Pros: Can assess the entire small intestine
  • Cons: Higher rate of false positives due to colonic fermentation; influenced by intestinal transit time

Glucose Breath Test

  • Pros: Higher specificity; less influenced by colonic bacteria
  • Cons: May not detect overgrowth in the distal small intestine

Clinical Considerations Test Selection

  • The choice between lactulose and glucose breath tests depends on clinical judgment and specific patient circumstances.
  • Some practitioners may prefer one test over the other based on their familiarity and the patient’s symptoms.

Results Interpretation

  • Both tests require careful interpretation by experienced clinicians to avoid misdiagnosis.
  • False positives and negatives can occur, so results should be considered alongside clinical symptoms and other diagnostic information.

Summary

Breath testing with lactulose and glucose provides a non-invasive and relatively simple method for diagnosing SIBO. Each test has its advantages and limitations, and the choice of test should be tailored to the patient’s needs and clinical presentation. Accurate interpretation of these tests is crucial for effective diagnosis and management of SIBO.   for the diagnosis of SIBO are available and have their own pros and cons.

For further detailed information, consult sources such as:

  • Pimentel, M., et al. “Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus.” The American Journal of Gastroenterology.
  • Lauritano, E. C., et al. “Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome.” Gut.

What is SIBO?

Posted on by Bradley Bush

Small Intestinal Bacterial Overgrowth (SIBO) is a condition where an excessive number of bacteria grow in the small intestine. While the large intestine is home to a rich bacterial population, the small intestine typically contains far fewer bacteria. When these bacteria overgrow in the small intestine, they interfere with digestion and nutrient absorption, leading to a variety of symptoms and health complications.

Common Symptoms of SIBO

  • Abdominal Bloating and Distention: Excess gas production by the bacteria leads to bloating and a sensation of fullness
  • Diarrhea: Bacterial overgrowth can disturb normal digestion, leading to frequent, loose stools
  • Constipation: Certain types of SIBO slow down intestinal motility, resulting in constipation
  • Abdominal Pain and Discomfort: Gas buildup and inflammation cause cramping and discomfort
  • Flatulence: Increased gas production by the bacteria leads to excessive passing of gas
  • Nausea: Disrupted digestion and bacterial byproducts can cause nausea
  • Fatigue: Nutrient malabsorption depletes energy, contributing to fatigue
  • Weight Loss: Persistent malabsorption and reduced appetite can lead to unintentional weight loss

Less Commonly Discussed Symptoms of SIBO

  • Gastroesophageal Reflux Disease (GERD) and Hiatal Hernias: SIBO can exacerbate GERD and sliding hiatal hernias due to increased intra-abdominal pressure from gas, impaired gut motility, and chronic inflammation.
  • Electrolyte Imbalance: SIBO can lead to diarrhea and malabsorption, causing imbalances in electrolytes like sodium and potassium.
  • Adrenal Fatigue: Chronic gastrointestinal distress from SIBO can strain the adrenal glands, leading to adrenal fatigue, which may affect hormone levels such as cortisol, DHEA, and aldosterone.
  • Nonalcoholic Fatty Liver Disease (NAFLD): SIBO can contribute to the development of NAFLD through chronic inflammation, increased intestinal permeability, and metabolic dysfunction.

Complications Caused by SIBO

  • Nutritional Malabsorption: Bacterial overgrowth disrupts nutrient absorption, leading to deficiencies.
  • Vitamin Deficiencies: Particularly of fat-soluble vitamins (A, D, E, K) and vitamin B12
  • Mineral Deficiencies: Poor absorption can lead to deficiencies in iron and calcium
  • Intestinal Permeability (Leaky Gut): Bacterial toxins and inflammation damage the gut lining, allowing larger molecules to pass through.
  • Chronic Inflammation: Persistent bacterial overgrowth triggers ongoing inflammation in the gut.
  • Blood-Brain Barrier Permeability: Lipopolysaccharides (LPS) from bacteria can increase permeability of the blood-brain barrier, allowing inflammatory molecules to reach the brain and affect the hypothalamus.
  • Neuroinflammation: Inflammation in the brain can disrupt hormone regulation, including cortisol production, by affecting the hypothalamus and pituitary gland.

Nutritional Malabsorption and Clinical Side Effects

  • Vitamin B12 Deficiency: Can cause anemia, fatigue, weakness, and neurological symptoms like tingling or numbness
  • Fat-Soluble Vitamin Deficiencies (A, D, E, K): 
    • Vitamin A: Leads to poor vision in low light and immune dysfunction
    • Vitamin D: Results in bone pain, muscle weakness, and a higher risk of fractures
    • Vitamin E: Can cause neurological issues and impaired immune response
    • Vitamin K: May lead to an increased tendency for bleeding and easy bruising
  • Iron Deficiency: Causes anemia, leading to fatigue, weakness, and pale skin
  • Calcium Deficiency: Results in weakened bones, increased fracture risk, and potentially osteopenia or osteoporosis
  • Protein Malabsorption: Can cause muscle wasting, edema, and overall weakness

 

Condition

SIBO Prevalence Rate

Health Study Controls

0-20%

Celiac disease

up to 67%

Crohn’s disease

up to 88%

Ulcerative Colitis

81%

Chronic Fatigue Syndrome

81%

Fibromyalgia

93%

Irritable Bowel Syndrome

up to 78%

Gastrectomy

63-78%

Connect Tissue Disease (e.g. Scleroderma)

43-55%

Diabetes Type II

up to 44%

Hypothyroidism

54%

Obesity

up to 41%

Rosacea

46%

Hypochlorhydria (drug-induced)

up to 78%

Summary

SIBO is characterized by excessive bacterial growth in the small intestine, leading to digestive discomfort, nutrient malabsorption, and a wide range of symptoms. The bacteria produce gasses and toxins that not only cause gastrointestinal issues but also contribute to more serious complications such as vitamin and mineral deficiencies, inflammation, and even neurological disturbances. Addressing SIBO is critical to restoring digestive health and preventing these long-term effects.