The Low FODMAP Diet: Negative Effects on the Gut Microbiome?



The Low FODMAP Diet: Negative Effects on the Gut Microbiome?


Irritable bowel syndrome (IBS) affects roughly 7-15% of the population and is the most common diagnosis made by gastroenterologists. (1) Symptoms of IBS include bloating/distention, constipation, diarrhea, flatulence, and abdominal pain. (1) For those with IBS, diet can play an integral role in triggering gastrointestinal symptoms with 60% of IBS patients reporting that certain foods trigger their symptoms. (1) Because the symptoms of IBS fluctuate, pharmacological treatments vary widely and drugs interventions often only target symptom relief and are inadequate. (1) Recently, clinical research has focused on different dietary patterns as a mean of managing IBS symptoms. One such diet that was developed for the management of IBS symptoms is the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyol (low FODMAP) diet. (1,2) Although the low FODMAP diet has shown promise in managing IBS related symptoms, clinical research suggests that long-term use of a how FODMAP diet negatively impacts the gut microbiome. (1,2,3)


What are FODMAPs?


FODMAPs are short-chain carbohydrates and sugar alcohols. FODMAP foods include fructose (fruits and vegetables), fructans (found in vegetables and grains), lactose (dairy), galactans (legumes) and polyols (artificial sweeteners). (1,2,3) For some individuals, FODMAPs have the potential to ferment in the colon during the digestive process. This process of fermentation draws water into the colon and produces carbon dioxide, hydrogen, and methane gas which causes IBS symptoms – bloating, gas, and pain. (1,2) FODMAPs are generally healthy foods that are found naturally in foods (fruits, vegetables, and whole grains) or are used as additives.


What is a low FODMAP diet?


The low FODMAP diet was developed based on the understanding that those with IBS symptoms have poor absorption of short-chain carbohydrates in the intestines leading to IBS related symptoms. (1,2,3) A low FODMAP diet aims to reduce such foods as a means of managing IBS symptoms. Although low FODMAP diets have shown to be effective in managing functional gastrointestinal symptoms (IBS), there are growing concerns about the long-term effects of such diet on overall health. (1) Due to the beneficial effects of fruits, vegetables, and whole grains on overall health and gut function, researchers have speculated whether a diet that restricts these health promoting foods is the most effective treatment in managing IBS symptoms. (2,3)


Negative Effects of a Low FODMAP diet:


In a systemic review, Marsh et al., (2016), noted that those following a low FODMAP had negative alterations in the gut microbiome. (1) It was discovered that those on a low FODMAP diet had reductions in beneficial bacteria (Bifidobacteria and Clostridial species) which are involved in the production of short chain fatty acids (SCFAs), the main fuel of gut bacteria. (1) Additionally, increases in IBS promoting bacteria, Ruminococcus torques, was seen in both the IBS patients and the healthy controls. (1,2) In a similar study, Staudacher et al., (2012), investigated the effects of fermentable carbohydrate restriction on the gut microbiota, SCFA production, and GI symptoms in patients with IBS. (3) Participants with IBS were placed on a low FODMAP diet or habitual diet for 4 weeks. After the 4 week intervention, stool testing determined that total luminal bacteria at follow-up did not differ between the groups, but it was observed that there were lower concentrations of beneficial Bifidobacteria in the intervention group compared to the controls. (3) These findings are concerning as Bifiodbacteria is one of the most abundant beneficial bacterial species in the human gut and alterations of Bifidobacteria will have negative implications on health beyond gut function.


It is apparent that the use of a low FODMAP diet can mitigate IBS symptoms, however studies have determined that long-term use of a low FODMAP diet results in negative alterations within the gut microbiome which may impact overall health. (1,2,3) Therefore, a low FODMAP diet should only be used when absolutely necessary and for short-periods of time with the addition of supplemental probiotic strains to address alterations within the gut microbiome.

1. Marsh, A., Eslick, E., & Eslick, G. (2016). Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis. European Journal of Nutrition, 55(3), 897-906.

2. Sloan, T. J., Jalanka, J., Major, G. A. D., Krishnasamy, S., Pritchard, S., Abdelrazig, S., . . . Spiller, R. C. (2018). A low FODMAP diet is associated with changes in the microbiota and reduction in breath hydrogen but not colonic volume in healthy subjects. PLoS ONE, (7).

3. Staudacher, H. M., Lomer, M. C. E., Anderson, J. L., Barrett, J. S., Muir, J. G., Irving, P. M., & Whelan, K. (2012). Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. Journal of Nutrition, 142(8), 1510.


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