Review Article

FODMAPS, Prebiotics and Gut Health—The FODMAP Hypothesis Revisited

Peter R. Gibson; Emma P. Halmos; Jane G. Muir

Disclosures

Aliment Pharmacol Ther. 2020;52(2):233-246. 

In This Article

Abstract and Introduction

Abstract

Background: Restriction of dietary FODMAP intake can alleviate symptoms in patients with irritable bowel syndrome. Because many FODMAPs have prebiotic actions, there is concern that their dietary restriction leads to dysbiosis with health consequences, and their intake is being encouraged by addition to foods and via supplements.

Aims: To examine the hazards and benefits of high and low FODMAP intake.

Methods: Current literature was reviewed and alternative hypotheses formulated.

Results: Low FODMAP intake reduces abundance of faecal Bifidobacteria without known adverse outcomes and has no effect on diversity, but the reduction in bacterial density may potentially be beneficial to gut health. Supplementary prebiotics can markedly elevate the intake of FODMAPs over levels consumed in the background diet. While this increases the abundance of Bifidobacteria, it adversely affects gut health in animal studies by inducing colonic mucosal barrier dysfunction, mucosal inflammation and visceral hypersensitivity. Rapid colonic fermentation is central to the identified mechanisms that include injury from high luminal concentrations of short-chain fatty acids and low pH, and inflammatory effects of increased endotoxin load and glycation of macromolecules. Whether these observations translate into humans requires further study. Opposing hypotheses are presented whereby excessive intake of FODMAPs might have health benefits via prebiotic effects, but might also be injurious and contribute to the apparent increase in functional intestinal disorders.

Conclusions: Reduced FODMAP intake has few deleterious effects on gut microbiota. Consequences (both positive and negative) of excessive carbohydrate fermentation in the human intestines from elevated FODMAP intake require more attention.

Introduction

In 2005, a collective group of dietary short-chain carbohydrates that are slowly absorbed in the small intestine or non-digestible due to inactivity or lack of hydrolases were described and termed FODMAPs (Fermentable Oligosaccharides, Monosaccharides, Disaccharides and Polyols).[1] A hypothesis was presented for their involvement in the pathogenesis of Crohn's disease. However, their ability to induce abdominal symptoms when consumed at usual dietary amounts in patients with irritable bowel syndrome (IBS) and the symptomatic alleviation that reliably occurs when they are reduced in the diet somewhat diverted attention away from potential harmful effects of FODMAPs on intestinal integrity.[2,3] Furthermore, the notion that at least the oligosaccharide components of FODMAPs are prebiotic for colonic microbiota raised concerns that strict restriction of their intake might be potentially harmful to health, in line with prebiotic concepts.[2] Hence, FODMAPs migrated from potentially inflammation-inducing to promoting of health. Recent studies in rats, mice and humans have once again indicated that FODMAPs might indeed be harmful to the colon. This is of particular relevance to prebiotic FODMAPs since these are being liberally added to the food supply, including baby formulas,[4] particularly as fructans (inulin, chicory root extract, fructo-oligosaccharide), with the view that they will promote health by favourable effects on gut microbial communities. Hence, the aim of this review is to revisit the FODMAP hypothesis and address the issue of whether too many FODMAPs might be harmful.

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