FODMAPs and SIBO
Content
1. What are FODMAPs?
2. What is SIBO?
2.1 SIBO Diagnostics
2.2 SIBO Treatment
3. FODMAPs and SIBO
3.1 low-FODMAP Diet
3.2 Other SIBO Diets
1. What are FODMAPs?
FODMAP stands for “Fermentable Oligo-, Di-, Monosaccharides and Polyols.” These are fermentable carbohydrates and sugar alcohols that are poorly absorbed in the small intestine and easily fermented by bacteria. This fermentation produces gas and can lead to a variety of symptoms, especially in patients with digestive conditions. FOS (fructooligosaccharides) and GOS (galactooligosaccharides) are common oligosaccharides found in high-FODMAP foods like onions, garlic, bananas, legumes, and oats. Lactose (a disaccharide), fructose (a monosaccharide), and polyols such as sorbitol and mannitol are also part of this group. When these substances are not fully digested, they reach the colon and interact with the gut microbiome. In cases where bacteria are present in elevated numbers in the small intestine, as in SIBO, fermentation occurs prematurely and produces excess gas, leading to abdominal discomfort.
Foods particularly high in FODMAPs include fruits like pears, apples, and cherries, as well as vegetables such as onions, artichokes, cauliflower, and beans. Legumes and cruciferous vegetables are known for their high FODMAP content and tendency to cause bloating. Dairy products and sweeteners like xylitol can also trigger symptoms. (1)
2. What is SIBO?
SIBO (Small Intestinal Bacterial Overgrowth) is a condition in which bacteria normally found in the colon overpopulate the small intestine. These bacteria ferment carbohydrates and produce hydrogen, methane, or hydrogen sulfide, which can result in abdominal pain, bloating, diarrhea, constipation, belching, fullness, and heartburn. SIBO shares many symptoms with IBS, making it a key differential diagnosis. Some patients may even be misdiagnosed with IBS when SIBO is the underlying cause.
2.1 SIBO Diagnostics
The diagnosis of SIBO is typically done through a breath testing method. Patients consume specific substances like lactulose, lactose, glucose, or fructose, which are then metabolized by bacteria. This bacterial metabolism results in the production of hydrogen or methane, which can be measured in the patient’s breath. Since human cells do not produce these gases, a positive rise in hydrogen or methane levels after carbohydrate consumption indicates bacterial overgrowth in the small intestine. Any elevated levels reflect bacterial activity.
2.2 SIBO Treatment
Several treatment approaches exist for SIBO, including targeted dietary interventions as well as the use of herbal or conventional antibiotics and antimicrobials. Treatment is customized based on the type of bacterial overgrowth and the patient’s specific symptoms. Furthermore, the type of gas produced (hydrogen, methane, or hydrogen sulfide) helps determine whether the dominant issue is SIBO or IMO (Intestinal Methanogen Overgrowth). A personalized diet strategy is often recommended to alleviate symptoms and support gut healing.
3. FODMAPs and SIBO
When bacteria are present in the small intestine, FODMAPs are fermented earlier than intended, leading to elevated gas levels and worsened symptoms. This can cause pain, bloating, and other negative effects on the digestive system. Reducing FODMAP intake can help limit bacterial fermentation and allow the gut to recover.
3.1 low-FODMAP Diet
The low-FODMAP diet is an approach developed to manage symptoms related to FODMAP intolerance and SIBO. As the name suggests, this diet focuses on reducing fermentable oligo-, di-, monosaccharides, and polyols in food intake. It begins with an elimination phase (4–6 weeks) where all high-FODMAP foods are avoided. Patients then move into a reintroduction phase to assess individual tolerance levels. Low-FODMAP foods include raspberries, melon, papaya, potatoes, pumpkin, and spinach. High-FODMAP foods like onions, apples, beans, and dairy are restricted in the initial phase. Although the diet does not eliminate bacterial overgrowth, it can reduce symptoms significantly by minimizing fermentation in the gut. (1)
The diet begins with a strict elimination phase lasting four to six weeks, during which all high-FODMAP foods are avoided. However, this diet is not intended as a long-term solution. After the initial phase, foods are gradually reintroduced to assess individual tolerance. The goal is to return to a balanced diet that includes some FODMAP-containing foods without triggering symptoms. (2)
The rationale behind using a low-FODMAP diet in SIBO treatment is to deprive bacteria of their preferred nutrients. This reduces bacterial metabolism, gas production, and toxin release, helping the gut to recover. However, the diet does not eliminate bacterial overgrowth itself but primarily alleviates symptoms.
Although research on the low-FODMAP diet specifically for SIBO is still limited (as of Summer 2024), it has been shown to have positive effects on other gastrointestinal conditions, such as irritable bowel syndrome (IBS). (3,4) The diet likely helps IBS patients by reducing gas production and minimizing irritation of the sensitive gut lining. Based on this, it is believed that a low-FODMAP diet may also be beneficial for SIBO symptom management. However, medical or dietary supervision is recommended when following this diet.
3.2 Other SIBO Diets
In addition to the low-FODMAP diet, several other dietary approaches can be used to support patients with SIBO. These include the Specific Carbohydrate Diet (SCD), SIBO-Specific Food Guide (SSFG), the Bi-Phasic Diet (BPD), and the Low-Fermentation Diet. Each of these approaches aims to reduce bacterial fermentation, improve gut health, and alleviate symptoms. Choosing the right diet should be done in contact with a healthcare professional familiar with SIBO and related conditions. For more details, refer to our dedicated article on SIBO diets and therapeutic options here.
References
- FODMAP-Tabelle-Blog.jpg (761×1200) (fodmap-info.de); zuletzt geprüft 17.08.2024; modifizierte Tabelle aus „Der Ernährungsratgeber zur FODMAP-Diät“ von Prof. Dr. med. Martin Storr
- Lucas Zapata P, García Navarro E, Ribes Koninckx C. The low-FODMAP diet. An Pediatr (Engl Ed). 2024 Jul;101(1):36-45. doi: 10.1016/j.anpede.2024.06.005. Epub 2024 Jun 20. PMID: 38906802.
- Staudacher HM, Whelan K. Altered gastrointestinal microbiota in irritable bowel syndrome and its modification by diet: probiotics, prebiotics and the low FODMAP diet. Proc Nutr Soc. 2016 Aug;75(3):306-18. doi: 10.1017/S0029665116000021. Epub 2016 Feb 24. PMID: 26908093.
- Ong DK, Mitchell SB, Barrett JS, Shepherd SJ, Irving PM, Biesiekierski JR, Smith S, Gibson PR, Muir JG. Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol. 2010 Aug;25(8):1366-73. doi: 10.1111/j.1440-1746.2010.06370.x. PMID: 20659225.
