SIBO Diagnosis: Fructose Testing
1. What is SIBO?
1.1 SIBO Diagnosis
1.2 SIBO Treatment
2. Fructose Malabsorption and SIBO Testing with Fructose
2.1 Procedure of the Fructose Breath Test
2.2 Interpretation of the Fructose Breath Test
2.3 Advantages and Disadvantages of the Fructose Breath Test
1. What is SIBO?
“Small Intestinal Bacterial Overgrowth” (SIBO) describes an abnormal bacterial colonization of the small intestine. Typical symptoms include abdominal pain, bloating, diarrhea, and constipation. A bacterial overgrowth in the small intestine means that bacteria, which typically populate the large intestine, colonize the small intestine. This can lead to the production of gases and toxins. While the large intestine of a healthy person is richly populated with bacteria, the small intestine is usually germ-free.
1.1 SIBO Diagnosis
Breath testing is the method of choice for diagnosing SIBO. In this test, the patient is given a sugary solution. The sugar is metabolized by bacteria, and the resulting gases enter the bloodstream and are exhaled. The substances used in the test include lactulose, lactose, glucose, or fructose. The breath test uses the fact that human cells do not produce hydrogen or methane. An increase in these gases in the breath, along with information about the timing of the increase, allows an experienced therapist to make conclusions about the presence of SIBO.
1.2 SIBO Treatment
Specially tailored diets, the use of herbal or conventional antibiotics, and probiotics are suitable for treating SIBO. The approach is individualized based on the patient and their symptoms.
2. Fructose Malabsorption and SIBO Testing with Fructose
Fructose is a monosaccharide absorbed in the human small intestine. The fructose transporter GLUT5 is required for this process. If there is a defect in this transporter, it leads to inadequate absorption of fructose in the small intestine (fructose malabsorption). The undigested fructose then reaches the large intestine of the digestive tract, where it is fermented by bacteria, leading to gas production and symptoms like diarrhea or bloating. This condition is commonly referred to as fructose intolerance. However, this form of fructose intolerance should not be confused with the hereditary, life-threatening condition known as hereditary fructose intolerance, which is caused by a genetic defect affecting fructose metabolism.
2.1 Procedure of the Fructose Breath Test
The fructose breath test for determining SIBO (small intestinal bacterial overgrowth) is conducted as follows: The patient initially provides a fasting breath sample. Then, the patient drinks a test solution containing a maximum of 25g (1) fructose in 250ml of water. Breath samples are then taken every 15 to 20 minutes over a period of approximately three hours (1).
2.2 Interpretation of the Fructose Breath Test
For the fructose breath test, an increase in the breath gases within the first 90-100 minutes indicates bacterial presence in the small intestine. If the levels of hydrogen exceed 20 ppm (1) or methane exceeds 12 ppm, a diagnosis of SIBO is likely. The earlier the increase in gas levels occurs, the more clearly it can be attributed to the presence of SIBO.
If the increase occurs after 120 minutes, a hydrogen increase of at least 20 ppm indicates fructose malabsorption.
2.3 Advantages and Disadvantages of the Fructose Breath Test
Whether the fructose breath test is suitable for SIBO diagnostics has not yet been scientifically clarified. The fact is that no human cell produces hydrogen or methane. Therefore, an increase in hydrogen or methane in the breath sample must be caused by bacteria. It is also generally accepted that the first 90/100 minutes of a breath test represent the small intestine.
In general, the breath test method is non-invasive and cost-effective compared to obtaining samples from the small intestine by endoscopy.
In my opinion, fructose testing can provide valuable initial information on the presence of SIBO.
References
- Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, Schmulson M, Valdovinos M, Zakko S, Pimentel M. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017 May;112(5):775-784. doi: 10.1038/ajg.2017.46. Epub 2017 Mar 21. PMID: 28323273; PMCID: PMC5418558.
