Review Article

Review Article: Dietary Fibre in the era of Microbiome Science

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


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

In This Article

Re-Introducing Fibre to the Western Diet

The Academy of Nutrition and Dietetics recommend that fibre is consumed in adequate amounts as part of a balanced diet. What does this actually mean? Reference intakes suggest 14 g of dietary fibre per 1000 kcal consumed, which equates to 25 g for females and 38 g for males, depending on energy intake.[64,65] The National Academy of Sciences Institute of Medicine similarly recommend 20-35 g/d[6] and the Scientific Advisory Committee on Nutrition (SACN) recommend 30 g/d.[66] Despite this, current dietary fibre consumption in socioeconomically developed societies, such as the United States of America, is estimated at only 12-18 g/d.[64,67,68] Figures in Europe vary but remain highest in Italy and lowest in Sweden and the UK general population.[69] In Africa, among rural South African and Ugandan populations, fibre is consumed in amounts greater than 50 g/d, which is associated with a reduced prevalence of chronic inflammatory disorders.[10,70] Contemporary consumption of dietary fibre remains far less than that exhibited by ancestral humans who had estimated intakes of up to 100 g/d.[71] The striking reduction in fibre consumption is partly attributable to changes in agricultural practices and production of fibre-based foods.[71] Reliance on energy dense, high glycaemic-load convenience foods is common in western society, largely replacing fibre and so recommended dietary fibre intakes are now seldom achieved.[65,72,73] Restoration of fibre after a prolonged period of dietary deficiency represents a significant challenge, not simply educational but also physiological.

Abrupt addition of or change in fibre intake leads to bloating, abdominal cramps and increased flatulence.[6,74] Furthermore, delayed gastric emptying and digestion, from soluble and viscous fibres, may aggravate symptoms of dyspepsia. This was identified in a small study where transient lower oesophageal sphincter relaxations were observed with fibre supplementation.[75] These unwanted symptoms are associated with many gastrointestinal and functional disorders and when coupled with negative social connotations of increased gas and flatulence may affect adherence. Clinical practice favours slow titration of fibre to achieve daily fibre intake in accordance with guideline recommendations.[6,64,65,66] Dietary fibre advice should not be glib and needs attention to detail for dose titration to avoid or reduce gas production and cramps, together with education on the expected benefits of fibre. Fibre intake guidelines as initial targets in clinical studies may allow future increases in doses that may even approach ancestral intake in appropriates individuals.