Low FODMAP Diets: The Pros (minimal) & Limitations (many)

I get asked about the low FODMAP diet every week, and there are some things to discuss about this controversial intervention – often used for those unpleasant gastrointestinal symptoms.

First, what is a low FODMAP diet?

FODMAP is an acronym which stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. The low FODMAP diet then means eating less of foods with these carbohydrates/ingredients. Historically, low FODMAP diets have been recommended for those with the label of Irritable Bowel Syndrome (which is a common misdiagnosis), Crohn’s disease or Ulcerative Colitis.

Low fodmap diets are tricky; there are some pros and cons (a lot more cons in my opinion) to them.

Pros:

• Patients can get initial relief about 75% of the time. By reducing carb foods that ferment a lot, then in turn less fermentation occurs and a decrease in GI symptoms should result
• Short term – only mean to be used for ~6 to 8 weeks so light is at the end of the tunnel shortly after starting

Cons:

• Not a long term solution
• Restrictive of nutrients
• Challenging to execute and tip toe around many (for the most part) healthy foods and create unnecessary food fear
• Doesn’t inherently address the “root cause” of symptoms especially if advised to follow this diet for a diagnosis of IBS (as IBS is often a misdiagnosis in the first place; In my opinion it is important to ask “what is the underlying culprit(s) convoluting the normal digestive process?”)
• In my experience and according to research, I’ve seen a lot of patients follow a low fodmap diet and it actually did a lot more harm then good because it can “starve out” a lot of the commensal aka good intestinal bacteria (as seen in patients’ FDA approved GIMAP tests). Sometimes, if constipation is the chief complaint – the issue actually gets worse with a long term low FODMAP diet.

Reality: High FODMAP foods are usually straws breaking the camel’s back to a deeply rooted gastrointestinal problem. It might not always be a diagnostic problem however, and rather a “functional” problem and if it doesn’t meet an ICD-10 code label, often times the care plan is lack luster.

In my practice, I order GIMAP tests to see if there is something present and there almost always is. According to the Cleveland Clinic & numerous other studies show 50-80% of IBS diagnoses are a misdiagnosis and/or not the full picture. Typically there is something else deeper like:

H. Pylori (clinical or subclinical)
Intestinal parasites
SIBO
Candida overgrowth
Celiac disease
Low MSH from a clinically significant toxic indoor mold exposure
Low stomach acid
Low mineral intake
Histamine intolerance
Heavy metal bioaccumulation
Basically, something more upstream that actually needs found, eradicated or properly managed. #test,dontguess

Once the root cause is found, then the low fodmap diet is usually a no longer needed. Band-Aid. Note it is in the scope of practice for Registered Dietitians to order these functional tests and provide medical nutrition therapy based interventions.

The low FODMAP diet does have a small time and place

I view it to be used temporarily for 6 to 8 weeks as an elimination diet for symptom relief only. Usually there will be less gas and bloating (as less high FODMAP foods that won’t trigger as much fermentation). So again, it can help with symptom relief, but the caveat should be (in my opinion) that more exploration should be occurring in the mean time.

Many doctors will recommend this low FODMAP diet for symptom relief – which I agree patients deserve relief in the moment! But I also think very thorough evaluation should also be occurring and it is important to be ruling out or ruling in things. Testing and not guessing is so important.

Bottom line:

Tread very carefully with the low fodmap diet and view it as a short term solution to utilize alongside a co-occurring deeper investigation. This will usually require working with a practitioner who is more functional medicine aligned. All in all, my lived professional experience is that Gastroenterology is the go to specialty for screening, diagnosing and managing gastrointestinal related diseases; however, when a patient doesn’t fully meet “disease criteria” it is with exploring a functional approach and considering the “subclinical” issues or dysfunctional problems that don’t perfectly fit in a box decided by the ICD-10 code Gods above.

In my experience, there is usually something else to be found and then an intervention more specific to the root problem can occur. Remember, symptoms such as these while common are not normal/ideal/healthy and should not be dismissed or taken lightly:

• bloating
• excess gas
• heartburn
• constipation
• diarrhea
• blood in stools
• abdominal pain

The low fodmap diet may “take off the edge” which is good but keep digging in the meantime.

If someone alone tells you to “do a food journal” as their main intervention to “pinpoint problem foods,” you should absolutely run! Find yourself a good functional medicine aligned dietitian and good Gastroenterologist for medical evaluation when needed.

References & Studies:

• https://pubmed.ncbi.nlm.nih.gov/20197761/
• Celiac disease misdiagnosed as IBS: https://pubmed.ncbi.nlm.nih.gov/38715591/
• https://pubmed.ncbi.nlm.nih.gov/37317843/
• https://pubmed.ncbi.nlm.nih.gov/28274108/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10357384/
• https://pubmed.ncbi.nlm.nih.gov/36014888/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9412469/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5495893/
• Parasites misdiagnosed as IBS: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856272/
• https://pubmed.ncbi.nlm.nih.gov/17070814/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7268507/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277457/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9413972/