Author: Melissa Zinda

Understanding Double Peak Patterns in Lactulose SIBO Breath Testing

Posted on by Melissa Zinda

When it comes to lactulose breath testing for Small Intestinal Bacterial Overgrowth (SIBO), one of the patterns that may emerge is the double peak. This refers to two distinct rises in gas levels during the breath test. The first peak occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as the lactulose reaches the colon. At this point, colonic bacteria begin their fermentation process. Although this double peak pattern was part of the diagnostic criterion for SIBO, improvements in testing methodology changed how these results are interpreted. While no longer considered definitive for diagnosing SIBO, the double peak still provides valuable insights into the overall health of the digestive system.

The Lactulose Breath Test Double Peak Explained

In a positive SIBO test, lactulose (a non-absorbable sugar) is fermented by bacteria in the small intestine. Within the first 120 minutes of testing, the fermentation causes the first rise or “peak” in hydrogen (H₂) or methane (CH₄) gases. This early gas production indicates excessive bacterial fermentation in the small intestine. As this area typically harbors fewer bacteria than the colon, this peak is considered abnormal. The second peak occurs when the remaining lactulose moves into the large intestine (colon). It is a normal result, reflecting healthy bacterial activity in the colon. However, extreme spikes in activity in the large intestines may indicate overgrowth/ abnormal activity. (See figure 1)

Classic double peak lactulose sibo breath test result
Figure 1: Classic double peak observed during a lactulose breath test. Two distinct rises in gas levels during the breath test are observed. Peak one occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as the lactulose reaches the colon, where colonic bacteria begin their fermentation process.

Double Peak Results: Transition from Diagnostic Use

Historically, a double peak was considered a clear indicator of SIBO. The idea was that if lactulose caused gas levels to rise in both the small and large intestines, bacterial overgrowth was present in the small intestine. However, with advancements in understanding SIBO and improved breath testing techniques, the double peak is no longer used as a primary diagnostic criterion. Now, research shows that the timing and levels of gas production can be influenced by multiple factors including gut motility and variations in the transit time of lactulose through the intestines.

Despite this, a double peak is still a common finding in breath testing. It can offer useful clinical information, especially for differentiating between small intestinal fermentation (indicative of SIBO) and colonic fermentation.

The Transition Period: 100-120 Minutes

One crucial aspect of lactulose breath testing is the transition period between 100 and 120 minutes. During this time, lactulose moves from the small intestine into the large intestine. This may result in a temporary drop in measurable gas activity often seen on breath test results. Levels drop because lactulose has finished fermenting in the small intestine but hasn’t yet begun in the colon.

This transition phase can be helpful for clinicians in interpreting results. For example, if a significant gas rise occurs before 120 minutes, it suggests bacteria in the small intestine are producing those gases. This rise is diagnostic for SIBO. However, if gas levels stay low or drop during the transition, then rise sharply after 120 minutes, it indicates fermentation in the large intestine. Fermentation in the large intestine is normal and expected. However, extreme increases may suggest irregularities.  Delayed transition periods can occur especially in patients with slow gut motility, constipation and gastroparesis (see Figure 2). 

Example of delayed double peak in SIBO breath test results
Figure 2: Double peak observed during a lactulose breath test. Baseline elevated hydrogen gas activity and transition period at 140 minutes suggest slow gut motility.

Importance of Differentiating Small vs. Large Intestinal Activity

Although the double peak is no longer a diagnostic requirement for SIBO, it remains valuable for assessing bacterial activity throughout the digestive tract. By analyzing both the early (small intestine) and late (large intestine) fermentation patterns, clinicians determine if bacterial overgrowth is confined to the small intestine or if other digestive issues, such as colonic dysbiosis, might also be present. The transition period between 100 and 120 minutes offers further insight. It helps pinpoint where gas production is happening—information that can guide diagnostic and treatment decisions.

Double Peak Case Study

Presentation: A 42 year old male with sudden onset of severe constipation, bloating, flatus and lower diffuse abdominal pain since food poisoning in the summer of 2023. 

After the first positive SIBO breath test, he was treated with a combination of herbal and prescriptive antibiotics and an herbal prokinetic. The patient reported initial symptom improvement and then progressively worsening constipation and bloating.                         

Retesting indicated lower gas activity from the previous breath test. However, an “elevated” baseline and late double peak indicate reduced gut motility and delayed intestinal emptying. Prescriptive prokinetic was begun with frequent monitoring (every 2-4 weeks) until motility improved without bloating. The goal is to eventually titrate off motility support over time. 

Prolonged double peak case study
Case Study Image 1: First breath test was a strong positive. Baseline levels are elevated.  Delayed emptying into the colon is indicated.
Double peak results indicating delayed colonic emptying
Case Study Image 2: Second breath test was negative. Baseline levels are elevated. Results indicate delayed emptying into the colon.

Conclusion

The double peak pattern in lactulose breath testing provides important clues about how bacterial fermentation occurs in both the small and large intestines. While no longer considered diagnostic for SIBO on its own, observing the timing and levels of gas production in relation to the transition period differentiates between small intestinal overgrowth and normal colonic fermentation. For patients with unexplained digestive symptoms, understanding these patterns guides effective treatment strategies, ensuring a more tailored approach to gut health management. Learn more about abnormal breath test patterns.

New Clinical Tool: Total SIBO Bacterial Load Measurement

Posted on by Melissa Zinda

Breath testing is a non-invasive diagnostic tool shown to be effective for diagnosing a number of conditions including Small Intestinal Bacterial Overgrowth (SIBO). Gas produced by intestinal bacteria diffuses into the bloodstream, passes through the lungs, and is excreted in the breath where it can be measured. SIBO is characterized by an excessive amount of bacteria in the small intestines, primarily anaerobic fermenting bacteria, that produce measurable gasses such as hydrogen and methane.

 

In the human gastrointestinal (GI) tract, hydrogen and methane gasses are produced by fermenting bacteria as a byproduct of breaking down carbohydrates that have not been fully digested. Bacteria in the gut ferment undigested carbohydrates, releasing atomic hydrogen (H) as a byproduct, which then combines to form molecular hydrogen (H₂). In certain cases, methane gas (CH₄) is produced when methanogenic archaea in the gut utilize hydrogen (H) as a substrate, combining it with carbon dioxide (CO₂) to create methane (CH₄). This process requires atomic hydrogen to first be released during fermentation, making atomic hydrogen a critical precursor for the creation of both hydrogen and methane gasses in the body. 

 

The amount of hydrogen produced in the gut and measured in breath testing, in the forms of H₂ and CH₄, provides data on a person’s bacterial activity. Although there are no published diagnostic criteria using total molecular hydrogen levels to date, it is relevant clinical data that increases the overall functionality of breath test results.

New Clinical Tool for Determining the Total SIBO Bacterial Load

After thousands of SIBO tests, Neurovanna has come to understand the clinical relevance of measuring the total amount of molecular hydrogen produced in both the small and large intestine. The Total SIBO Bacterial Load was developed to help healthcare providers visualize this data and develop more personalized diagnostics and treatment. This unique assessment:

  • Allows for comparisons between optimal and elevated SIBO populations
  • Provides insight into bacterial activity within the large intestine
  • May help predict the potential for die-off reactions to treatments

 

Optimal vs Elevated SIBO Populations

Image showing Total SIBO Bacterial Load graph found on a report

In order to provide clinical value, it is necessary to have ranges with which to compare patient values. Neurovanna generated both optimal and elevated ranges for molecular

 hydrogen from 200 randomly selected breath tests from each diagnostic criteria: glucose SIBO positive, glucose SIBO negative, lactulose SIBO positive and lactulose SIBO negative. As a result, the SIBO breath test reports for both lactulose and glucose include an assessment of the Total SIBO Bacterial Load. Each assessment plots the patient values representing the total molecular hydrogen (H₂) measured for each breath sample against the ranges for the optimal and elevated hydrogen activity over time allowing for comparison between populations. See figure 1.

By comparing the timing and concentration of hydrogen gas in individuals versus a normal population, clinicians can detect fermentation patterns indicative of gastrointestinal abnormalities.

Elevated Bacterial Load in the Large Intestine Indicates Gastrointestinal Abnormalities 

Total hydrogen gas activity can be elevated in the large intestine due to various gastrointestinal abnormalities including: microflora dysbiosis (natural or post-antibiotic), parasitic infections, food maldigestion, food allergies, sugar malabsorption (e.g. lactose intolerance), and disturbances like post-food poisoning or traveler’s diarrhea. Figures 1-5 provide examples commonly seen in SIBO and/or large intestinal bacterial overgrowth (LIBO) positive individuals. Here’s how each of these factors contributes to elevated hydrogen gas.

Dysbiosis and Microflora Imbalances: Dysbiosis, an imbalance of gut bacteria, can cause excessive fermentation of undigested carbohydrates in the large intestine, leading to increased hydrogen gas production. This occurs when harmful bacteria overgrow or beneficial bacteria are reduced, causing disruptions in normal digestion.

Parasitic Infections: Infections from parasites like Giardia can disrupt digestion, causing malabsorption of nutrients. This undigested food reaches the large intestine, where bacteria ferment it, resulting in elevated hydrogen gas levels.

Food Maldigestion: Insufficient production of digestive enzymes (e.g., from pancreatic insufficiency) can lead to undigested carbohydrates entering the colon, where bacteria ferment them, increasing hydrogen gas production.

Food Allergies: Food allergies can cause inflammation in the gut, impairing digestion and leading to malabsorption. As undigested food reaches the large intestine, fermentation by gut bacteria increases hydrogen gas levels.

Lactose Intolerance: In individuals with lactose intolerance, the inability to properly digest lactose results in it reaching the colon undigested. Colonic bacteria ferment lactose, leading to excessive production of hydrogen gas, often causing bloating and discomfort.

Post-Food Poisoning or Traveler’s Diarrhea: Following food poisoning or traveler’s diarrhea, the gut microbiome may be disrupted, leading to malabsorption and bacterial overgrowth. This can result in increased fermentation of carbohydrates in either the small and/or large intestine and elevated hydrogen gas levels.

Graph showing a late rise, positive SIBO result Graph showing a negative SIBO, positive LIBO result

Bacterial Load Predicts Bacterial Die-Off Reactions

 

Hydrogen gas levels can provide insights into the severity of bacterial overgrowth (bacterial load) in SIBO/LIBO and may also be predictive of die-off (Herxheimer) reactions during treatment. 

Hydrogen Gas Levels and Overgrowth Severity

Higher hydrogen gas levels during a breath test can indicate a greater bacterial load in the small intestine. The more bacteria present in the gut, the more fermentation of carbohydrates takes place, resulting in the release of hydrogen gas. In this way, elevated hydrogen levels can reflect the extent of bacterial overgrowth, with higher levels generally suggesting more severe overgrowth.

 

For instance, a rapid and significant rise in hydrogen gas levels shortly after consuming a fermentable substrate (like glucose or lactulose) is often associated with a larger population of hydrogen-producing bacteria, particularly in the small intestine.

 

Predictive of Die-Off (Herxheimer) Reactions

Graph showing a high positive SIBO & LIBO resultHerxheimer reactions or die-off occur when large numbers of bacteria are killed rapidly during treatment (such as with antibiotics or herbal antimicrobials). Patients with higher molecular hydrogen levels, indicating a higher bacterial load, may be at greater risk of experiencing more pronounced die-off reactions during treatment. As more bacteria are killed off in a short period, there is an increased likelihood of releasing toxins into the body, triggering inflammatory responses and worsening symptoms like fatigue, headaches, bloating, and body aches (Figures 1, 3 & 4). 

 

Monitoring hydrogen gas levels before treatment can help predict the intensity of these reactions. Patients with very high hydrogen levels may need a slower introduction to treatment or supportive measures such as detox protocols or liver support, to manage die-off symptoms.

 

While it is difficult to predict exactly how patients will respond to treatment, the total bacterial load can provide some guidance. A general rule is that the higher the total bacterial load, the greater the likelihood of experiencing bacterial die-off (Herxheimer) reactions (Figures 1, 3, & 4). Alternatively, the lower the bacterial load the less likelihood there is of experiencing bacterial die-off (Herxheimer) reactions. For example, the lack of colonic activity shown in figures 2 and 5 suggest a less complicated clinical presentation and greater chance of successful SIBO treatment with lower chance of SIBO recurrence. 

Graph showing a low positive SIBO & LIBO result

Summary

In conclusion, elevated hydrogen gas activity throughout the gastrointestinal tract can result from a variety of factors, including digestion issues, malabsorption, bacterial imbalances, colon diseases, and parasitic infections. Measuring hydrogen gas levels provides valuable insight into the severity of bacterial overgrowth in the small and large intestines and can serve as a predictive tool for treatment-related reactions such as Herxheimer (die-off) responses. Patients with higher hydrogen levels often have a larger bacterial load, which can increase the likelihood of more intense die-off reactions during treatment, underscoring the importance of personalized care to manage symptoms.

Hydrogen gas measurement not only aids in diagnosing SIBO but can also help identify other underlying gut conditions, such as dysbiosis in the large intestine, parasitic infections, or sugar malabsorption disorders like lactose intolerance. Monitoring hydrogen levels can guide healthcare providers in creating a more tailored and holistic treatment plan, which may include additional testing for colon infections, additional support for patients undergoing SIBO treatments, targeted therapies for imbalances, or adjustments to manage food malabsorption. Ultimately, the integration of tools like the Neurovanna Total Bacterial Load provides a deeper understanding of gut health, improving outcomes for patients with SIBO, LIBO, and related gastrointestinal disorders.

The Total SIBO Bacterial Load is unique to Neurovanna. If you are a healthcare provider interested in using non-invasive breath testing to assess SIBO and/or LIBO, set up a Neurovanna account. If you are a patient interested in testing with Neurovanna, ask your doctor to complete this referral form or contact us to find a doctor near you.