Review Article

Review Article: Dietary Fibre in the era of Microbiome Science

John O'Grady; Eibhlís M. O'Connor; Fergus Shanahan

Disclosures

Aliment Pharmacol Ther. 2019;49(5):506-515. 

In This Article

Abstract and Introduction

Summary

Background Explanations for the health benefits of dietary fibre have, in the past, been inconsistent and studies of the physiological effects of dietary fibre were, perhaps, directed at the wrong read-outs. Confounding factors included a failure to appreciate the molecular diversity and varied properties of fibre-types and the role of fibre as a substrate for microbial metabolism in the gut.

Aim To present a modern perspective on fibre science and to encourage clinicians to re-consider the health impact of dietary fibre and how best to approach adjustments in dietary consumption.

Methods This perspective is drawn selectively from recent microbiome science; no attempt was made to perform an exhaustive review of all articles related to every aspect of dietary fibre.

Results Advances in microbiome science have revealed not only the functional impact of dietary fibre on the composition and function of the microbiota but have also demonstrated the physiologic responses to microbial-derived metabolites from fibre digestion. Moreover, studies have shown the personalised nature of host responses to dietary fibre intervention, with outcomes being dependent on individual pre-treatment gut ecology.

Conclusions The physical properties of dietary fibres are important for homeostasis within the gut, but the predominant health benefits extend beyond the gut to enhanced metabolic welfare, including protection against obesity and related metabolic diseases. Fibre is a form of functional food joining a growing list of examples of diet-microbe-host interactions which link microbe-host metabolic and immune cascades.

Introduction

Once was a time when gastroenterologists regarded (or disregarded) dietary fibre as the undigested component of natural foods which gave the colon a good work-out. Fibre was seen to add bulk to stools and to promote orderly bowel function, by which regular bowel habits was intended and was in some vague way good for health in general and for "functional" bowel disorders, in particular. Those who were privileged to hear the iconic Denis Burkitt were struck by the Irishman's persuasive rhetoric, refreshing in its directness and simplicity: "if you pass small stools (low dietary fibre) you have to have large hospitals."[1] Then followed a period of disappointment, when dietary fibre seemed to be unhelpful in irritable bowel syndrome[2] and other presumed clinical benefits could not be demonstrated. As these cold facts emerged, Burkitt's stock was in decline and viewed, by some, as "hot air".[3] Sadly, few gastroenterologists considered the details behind dietary fibre science. What is the appropriate dose of fibre for a healthy diet? Is there a difference between soluble and insoluble fibre? What is fibre and what happens to it in the human gut? Today, Burkitt's star is rising again and fibre science is undergoing a remarkable phase of revisionism in light of developments in microbiome science. With the expanding knowledge of diet-microbe-host interactions, clinicians once again have to consider the health impact of dietary fibre and how best to advise regarding adjustment of dietary consumption.

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