Why a Low FODMAP Diet Might Not Work for IBS
Last updated: April 2023
A low FODMAP diet is a go-to diet for the treatment of irritable bowel syndrome (IBS). It involves reducing foods with high amounts of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, which can make IBS symptoms worse.1
Studies have shown that a low FODMAP diet can offer symptom relief for 70 percent of people with IBS, showing improvements in pain, diarrhea, and bloating.1
When a low FODMAP diet doesn’t work
What happens when you are in the 30 percent of people with IBS for whom the low FODMAP diet doesn’t work?
In my professional experience with patients, you will know whether the low FODMAP diet has helped you during the 2 to 6 weeks you follow the diet. While you are going through the diet, it’s important to rate your symptoms before, during, and after the diet.
It’s also important to understand that outside factors can influence symptoms, such as stress levels or anxiety, other illnesses, hormone fluctuations in women (especially around the time of their period), and other factors.2
If you are not sensitive to FODMAPs, your symptoms should not come back when you reintroduce foods that contain them.1
Before ruling out FODMAPs, it’s important to assess whether you were 100 percent compliant with the diet. The best way to ensure compliance and be sure you are following the diet correctly is to work with a qualified nutritionist or dietitian.
If you were compliant, then it’s time to rule out other conditions that have similar symptoms, such as celiac disease, inflammatory bowel disease, and endometriosis. Once these are ruled out, then other scenarios can be explored.
Is it SIBO?
Small intestine bacterial overgrowth (SIBO) has been found to be a contributing factor in those with IBS. SIBO occurs when bacteria that should mainly be located in the large intestine are found in the small intestine. The fermentation from bacteria results in similar symptoms as those of IBS, such as bloating, pain, and altered bowel movements.3
SIBO is usually diagnosed through a hydrogen breath test. If the test is positive, then you may be prescribed antibiotics or herbal antimicrobials to clear the overgrowth. This treatment is combined with a diet. This might include the FODMAP diet, but your health practitioner may also remove other forms of carbohydrates, such as starch, resistant starch, sugar, soluble fiber, and prebiotics. It is best to work with a health practitioner if you suspect SIBO.3
Is it a food chemical?
Food chemicals such as histamine, salicylates, glutamates, amines, and certain food additives can cause food reactions.4
Diagnosing an intolerance to a food chemical such as salicylate intolerance is done using a low chemical elimination diet. Food chemicals can be reintroduced systematically and quantities tested to see which foods are safe and to determine how much you can eat of a certain food without triggering your symptoms.
Is it a yeast overgrowth?
The most well-known form of yeast overgrowth is candida overgrowth (candidiasis). Symptoms may include constipation, diarrhea, nausea, flatulence, and bloating. But there is also a range of other symptoms such as fatigue, oral thrush, recurring genital, or urinary tract infections.5
In my opinion, one way to treat candida overgrowth is to eliminate sugar. Taking certain supplements, such as garlic, probiotics, and pomegranate, may also help. It is best to work with a qualified health practitioner if you suspect candida.
What else could it be?
Additionally, your health practitioner may want to test your liver function or test for parasites or an overgrowth of certain bacteria species.
Has the low FODMAP diet worked for you? Tell us your story:
Do you suffer from IBS-C, IBS-D, or IBS-Mixed/Alternating?