The effectiveness of prebiotics in modifying the gastrointestinal microbiota for the management of digestive disorders
The June Nutrition Society Paper of the month is the Sir David Cuthbertson Medal Lecture published in Proceedings of the Nutrition Society and is entitled ‘ Mechanisms and effectiveness of prebiotics in modifying the gastrointestinal microbiota for the management of digestive disorders’
The gastrointestinal (GI) microbiota is a complex and metabolically active ecosystem that plays an important role in health and disease. The microbiota vary in number, diversity, composition and activity depending on the region of the GI tract. One of the biggest advances thus far has been the comprehensive metagenomic sequencing of the GI microbiota by the MetaHIT Consortium (http://www.metahit.eu/), which demonstrated that any of 1,000-1,150 different bacterial species could populate the human GI tract, with each individual harboring approximately 160 different species.
Extensive research has demonstrated a role for specific dietary carbohydrates in modifying the microbiota, first described as the prebiotic concept in 1995. Prebiotics are non-digestible, fermentable food components that result in ‘the selective stimulation of growth and/or activity of one or a limited number of microbial genera/species in the gut microbiota that confer health benefits to the host’
Marked alterations of the luminal microbiota have been demonstrated in patients with digestive disorders, including higher Clostridia in patients who develop diarrhoea during enteral nutrition and the influence of bifidobacteria on intestinal dendritic cell phenotype in Crohn’s disease. Although the impact of prebiotics on the intestinal microbiota of healthy people has been extensively investigated, relatively few studies have addressed their role in digestive disorders, and those that have do not always replicate the microbiological findings in healthy subjects.
For example, in enteral nutrition, where diarrhoea is a common complication, some trials have shown that prebiotics have little impact on bifidobacteria or short-chain fatty acid concentrations. In active Crohn’s disease, two randomized controlled trials have shown no impact of inulin/oligofructose on gastrointestinal bifidobacteria, indeed both studies showed greater withdrawal in the prebiotic groups. Meanwhile in irritable bowel syndrome, two trials of inulin-type fructans found no significant impact on symptoms (indeed in one study, high doses actually worsened symptoms), whereas two trials of low doses of prebiotics showed symptom improvement.
Unlike healthy humans, patients experience a number of issues that may alter their gastrointestinal microbiota (disease, antibiotics, inflammation) and the use of microbiota modifying therapies, such as prebiotics, do not always elicit the same effects in patients as they do in healthy people. It is important that health professionals use the results of robust trials to inform their clinical decision-making regarding prebiotic use in digestive disorders and use the compound and dose in the population originally investigated.
This paper is freely available for one month
Each month a paper is selected by one of the Editors of the five Nutrition Society Publications (British Journal of Nutrition, Public Health Nutrition, Nutrition Research Reviews, Proceedings of the Nutrition Society and Journal of Nutritional Science). This paper is freely available for one month.