Low FODMAP Diet For SIBO - Does It Actually Help?

What is a Low FODMAP Diet? 

The low FODMAP diet was developed by researchers out of Monash University in Melbourne, Australia. The term ‘FODMAP’ is an acronym that stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.

FODMAPs are short-chain carbohydrates made up of 1-10 sugars found in several common foods.1 These specific carbohydrates may worsen IBS symptoms by increasing intestinal water and gas content, resulting in distention, bloating, and abdominal pain.

The diet has been used with success to improve irritable bowel syndrome (IBS) symptom control in 50-80% of IBS sufferers. 2

Examples of FODMAPs and their primary sources

How do you do a low FODMAP diet?

A low FODMAP diet is a 3-phased plan which restricts (phase 1), challenges (phase 2), and then reintroduces FODMAPs found in several common foods (phase 3). The diet's end goal is to maintain IBS symptom control while expanding food options as much as possible.

Phase 1

• In phase 1 of the diet, low FODMAP foods are eaten in place of high and moderate FODMAP-containing foods. 
• High and moderate FODMAP containing foods are restricted from the diet for 2-6 weeks. Phase 1 of the diet is not intended to be followed over the long term. 
• Those who respond to the diet in phase 1 with improved symptom control move on to phase 2. 
• Those who do not respond with symptom improvement in phase 1 of the diet are advised to entirely abandon the low FODMAP diet and resume a regular diet. 

Phase 2

• Phase 2 lasts for 6-8 weeks and is used to identify which specific FODMAPs may be triggering IBS symptoms. 
• For this phase, the overall diet remains low in FODMAPs. Food challenges are staged with foods containing moderate and then high amounts of only 1 FODMAP group at a time. This helps to identify which FODMAPs are tolerated and which are not.

Phase 3

• In phase 3 of the diet, well-tolerated FODMAP-containing foods are added back into the diet. Only poorly tolerated FODMAP-containing foods remain restricted. 
• Phase 3 is ongoing. Some people may initially have sensitivities to certain foods that could potentially improve over time. Repeated challenges of poorly tolerated foods are recommended every 3-6 months.
  

Why might the low FODMAP diet help SIBO?

The low FODMAP diet was not initially intended for the management of SIBO. However, there is considerable overlap between IBS and SIBO symptoms. Common symptoms for both conditions include: 

• Abdominal Pain
• Bloating
• Flatulence
• Diarrhea and/or Constipation
• 3

It’s thought that the low FODMAP diet may improve SIBO symptoms by reducing the intake of highly fermentable, short-chain carbohydrates (FODMAPs). This could minimize bacterial fermentation in the small intestines, reducing symptoms such as gas, bloating, and abdominal pain.3

Adding to this, studies have found that IBS sufferers have higher odds of having SIBO.4 However, the prevalence of SIBO in IBS is a matter of debate.

• A meta-analysis published in 2020 looked at the prevalence of SIBO in individuals with IBS. 4 
• This meta-analysis reviewed 25 studies, which included 3,192 patients with IBS and 3,320 control subjects. People with IBS had 4.9 times the odds of having SIBO compared against healthy controls. 4 
• The study noted the low quality of evidence used to determine these odds, partly due to differences in study design and error-prone diagnostic tests.4 
• Breath tests may potentially over or under-diagnose SIBO depending on the type of carbohydrate ingested for the test (lactulose vs. glucose, respectively). 4 
• Culture-based techniques can also be prone to errors or challenges in interpretation due to contamination of samples from the mouth and studies using different culture-based cutoffs for diagnosis. 4 
• We should interpret these prevalence risks cautiously, but the information available to date has found that people with IBS are more prone to having SIBO. 4
  

What does the research say? 

We are unaware of any studies to date that have explored the use of a low FODMAP diet to treat or manage SIBO.

Monash University holds the position that low FODMAP diets might be used as symptom management aids for SIBO.3 In these cases, it is recommended that a low FODMAP diet be carried out under the supervision of a registered dietitian. Special care should be taken to ensure the diet remains balanced and that any nutritional inadequacies created by SIBO are addressed.

The diet should follow the standard 3-phased approach. However, if no symptom improvement is noted after completing phase 1 of the diet, it is recommended to abandon the low FODMAP diet and return to a regular diet.3

The low FODMAP diet should not be misconstrued as a treatment option for SIBO, as there is no evidence to support this claim. Monash University also suggests that only one intervention should be tried at a given time -- diet or otherwise-- to pinpoint which intervention offers relief. 3

The diet’s usefulness should be based on symptom improvement, not breath test measurements which can be highly error-prone.3

Our verdict

• The low FODMAP diet may improve SIBO symptoms by reducing highly fermentable, short-chain carbohydrates (FODMAPs) in the diet.
• The reduction in bacterial fermentation is what is thought to reduce symptoms like gas, bloating, and abdominal pain.
• We are unaware of any studies to date that have explored the use of a low FODMAP diet to treat or manage SIBO.
• A low FODMAP diet might be helpful in the management of symptoms in SIBO. 
• If a low FODMAP diet trial is undertaken for SIBO symptom management, we recommend the diet be supervised by a registered dietitian. 
• The low FODMAP diet should not be misconstrued as a treatment for SIBO as there is no evidence to support this claim. 
• Response to the diet should be measured based on symptom improvement, not breath test results.