J Neurogastroenterol Motil 2024; 30(3): 379-380  https://doi.org/10.5056/jnm24009
Predicting Response to Low Fermentable Oligo-, Di-, Mono-saccharides, and Polyols Diet in Patients With Abdominal Bloating Using Hydrogen Methane Breath Test: Is a Spot Sample Enough?
Uday C Ghoshal,1,2* Uzma Mustafa,1 Subhra K Mukhopadhyay,1 and Mahesh K Goenka1
1Institute of Gastrosciences and Liver Transplantation, Apollo Multispeciality Hospitals, Kolkata, India; and 2Department of Microbiology, The University of Burdwan, Burdwan, West Bengal, India
Published online: July 30, 2024
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

TO THE EDITOR: Somvanapanich et al1 showed that a 2-hour post-lunch spot hydrogen (H2) and methane (CH4) breath test predicted response to low fermentable oligo-, di-, mono-saccharides, and polyols (FODMAP) diet. While we acknowledge its significance, we have a few comments.

In this study, the spot breath test was performed after usual non-standardized lunch.1 The variable amount of “FODMAPs” in the non-uniform meals might influence the diagnostic accuracy of the test. Also, the comparison of outcomes across studies may be difficult.

The FODMAP content in a meal does not depend only on food types but also on serving sizes (https://www.monashfodmap.com/ibs-central/i-have-ibs/get-the-app/). A specific food may be classified as low-FODMAP at a particular serving size, moderate-FODMAP at a larger size, and high-FODMAP at a greater size.

About 40% of gastric emptying occurs during the initial 2 hours after meal and 90% by 4 hours.2 Fermentation of FODMAP largely occurs in distal gut.3 In our recent study on FODMAP-meal challenge test, we observed that rise in breath H2 was most prominent after the first 4 hours of ingestion of a standardized high FODMAP meal.4 Somvanapanich et al1 claimed that they replicated their previous protocol wherein, rise in breath H2 was not observed after breakfast until 2 hours post-lunch.5 However, it raises a question whether 2-hour post-lunch rise is exclusively attributed to lunch and not influenced by the breakfast. Moreover, assuming that a small portion of lunch meal reached the distal small bowel 2-hour post-lunch, it could cause “FODMAP stacking effect” to the breakfast meal.1 “FODMAP stacking effect” refers to adding up FODMAPs in the gut before manifesting into symptoms.

Interestingly, 6/21 responders (28.57%) had constipation-predominant irritable bowel syndrome (IBS-C).1 Most studies showing benefit of low-FODMAP diet included non-IBS-C patients.4

The major food items consumed in this study were animal proteins and rice, which are low in FODMAP though high FODMAP additives might be used in preparation.1 High-protein diets might shift carbohydrate to protein fermentation by gut bacteria.6-8 A possibility of high FODMAP food additives or protein foods might cause the observed rise in breath gases.

The sensitivity observed by Somvanapanich et al1 (66.7%) is lower than our study (78%).4 The above-mentioned factors might explain the difference in sensitivity in these 2 studies.1,4 We believe that studying breath H2 over a longer duration along with symptoms generation is expected to predict microbial metabolic index in the gut lumen and visceral hypersensitivity to predict response to a low-FODMAP meal as reported by us recently. 4


Uzma Mustafa thanks GastroLab India Pvt. Ltd. for supporting her.

Financial support


Conflicts of interest

Uday C Ghoshal have patent application for BreathCalc and FODMAP meal challenge test. None of the other authors declare any conflict of interest.

Author contributions

Uday C Ghoshal conceptualized, reviewed literature, and contributed to drafting and editing the manuscript; Uzma Mustafa reviewed literature and helped to write the first draft; Subhra K Mukhopadhyay and Mahesh K Goenka provided critical input while writing and edited the paper. All the authors read the final version of the paper.

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  4. Ghoshal UC, Mustafa U, Mukhopadhyay SK. FODMAP meal challenge test: a novel investigation to predict response to low-FODMAP diet in non-constipating irritable bowel syndrome. J Gastroenterol Hepatol 2024;39:297-204.
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  6. Gilbert MS, Ijssennagger N, Kies AK, van Mil SWC. Protein fermentation in the gut; implications for intestinal dysfunction in humans, pigs, and poultry. Am J Physiol Gastrointest Liver Physiol 2018;315:G159-G170.
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  7. Beaumont M, Portune KJ, Steuer N, et al. Quantity and source of dietary protein influence metabolite production by gut microbiota and rectal mucosa gene expression: a randomized, parallel, double-blind trial in overweight humans. Am J Clin Nutr 2017;106:1005-1019.
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  8. Geypens B, Claus D, Evenepoel P, et al. Influence of dietary protein supplements on the formation of bacterial metabolites in the colon. Gut 1997;41:70-76.
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