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Selection of naturally conserved fermented foods in jars
October 17, 2019

The current state of prebiotics

In the third of a four-part CME series titled, "The Microbiome and Digestive Health: A Look at Prebiotics," Bridgette Wilson, PhD, RD, and Kevin Whelan, PhD, RD, cover the current state of prebiotics.
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This article is the third of a four-part CME series on prebiotics. This educational activity is supported by an educational grant from GlaxoSmithKline. Part 1, “Prebiotics 101,” and Part 2, “Diet vs. Prebiotics,” are available through AGA University.

Authors
Bridgette Wilson, PhD, RD
Postdoctoral Research Associate in Nutritional Sciences
King’s College London
Kevin Whelan

Kevin Whelan, PhD, RD
Professor of Dietetics
King’s College London

Introduction

Prebiotics are “substrates that are selectively utilised by host microorganisms conferring a health benefit.” Two key components of the definition are their selective utilisation and conferring a health benefit. The health benefit may be derived through:

1. Promotion of numbers of certain microbes;
2. Production of microbial metabolites (e.g. butyrate) that may benefit the host; or
3. Direct interaction with mucosal immune-modulatory receptors.

The two most studied classes of prebiotics are the inulin-type fructans (ITF) and β-galacto-oligosaccharides (GOS).

Utility of prebiotics in clinical settings

Prebiotics are not digested in the small intestine and arrive largely intact in the colon, where they promote the growth of beneficial bacteria such as bifidobacteria, increase short-chain fatty acid production, which may support cell cycle regulation, and improve immune function as measured by increased faecal IgA.

Key conditions for which prebiotics are studied

Prebiotics are being investigated for their use in conditions where microbiota and short-chain fatty acid production differ compared to healthy controls, e.g., gastrointestinal (GI) disorders, metabolic syndrome, and aging/immune senescence.1 Patients with GI disorders may have overt or subclinical intestinal inflammation and typically have fewer bifidobacteria than healthy controls. Therefore, these patients could benefit from the anti-inflammatory and bifidobacteria-augmenting effects of a prebiotic. Further, patients taking a probiotic could consider taking a prebiotic alongside (so-called “synbiotic”).

Irritable bowel syndrome. Irritable bowel syndrome (IBS) is a prevalent, chronic gastrointestinal disorder in which prebiotics have been investigated. A recent meta-analysis of 11 clinical trials has shown that prebiotics increase faecal bifidobacteria but generally do not improve IBS symptoms. However, lower doses (<6 g/d) of non-ITF prebiotics (e.g., GOS, pectin, partially hydrolysed guar gum) may reduce flatulence, whereas ITF prebiotics (e.g., FOS, oligofructose, inulin) increase flatulence.2

ITF and GOS prebiotics are short-chain fermentable carbohydrates, or FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols). Interestingly, a diet that restricts FODMAPs has been shown to improve IBS symptoms despite reducing bifidobacteria concentration and lowering short-chain fatty acids.3,4 In a comparative four-week trial, supplementation with GOS prebiotics alone also significantly improved IBS symptoms, similar to the low FODMAP diet; however, unlike the low FODMAP diet, there was an increase in faecal bifidobacteria.5

Constipation. Two studies in elderly patients with defecation difficulties or constipation have demonstrated an increase in stool frequency and a shift towards softer stool when prebiotics were taken at doses ≥ 10 g/d.6,7 However, a meta-analysis of seven clinical trials did not show prebiotics to be superior to placebo, possibly due to underpowering of studies.8

Inflammatory bowel disease. In active Crohn’s disease, prebiotics do not improve clinical outcomes and at high doses may make some gastrointestinal symptoms worse. However, prebiotics have been shown to beneficially modulate markers of intestinal immunity such as increased IL-10 and decreased IL-6.9 In ulcerative colitis, prebiotics are well tolerated although there is no evidence of clinical benefit in large trials. There may be a reduction in inflammation when prebiotics are added to standard care.10

Overall, additional clinical studies are needed to better understand which prebiotics, alone or in combination, may be most effective for patients with GI disorders.

Talking points to use with your patients
  • Different prebiotic supplements have different effects on gut symptoms. For example, lower doses of non-inulin type fructans (e.g., GOS, pectin, partially hydrolysed guar gum) are likely to be better tolerated in patients with functional gut symptoms including IBS.
  • Though prebiotic-containing foods are thought to benefit gut health in general, some prebiotics are FODMAPs that have been associated with symptoms in IBS patients. Individual patients on restrictive diets should systematically introduce prebiotic foods to identify the type and quantity they can tolerate.
  • Prebiotic supplementation of ≥ 10 g/d may soften stools and increase bowel movements in patients with defecation difficulty or constipation.
  • Prebiotic supplementation may worsen symptoms in Crohn’s disease but is well tolerated in ulcerative colitis, although there is no effect on disease activity.

To claim your CME credits for this activity, please visit AGA University.

Key further reading
 
References

1. Peterson, C.T., Sharma, V., Elmen, L. Peterson, S.N. Immune homeostasis, dysbiosis and therapeutic modulation of the gut microbiota. Clin Exp Immunol. 2015;179(3):363-77.

2. Wilson, B., Rossi, M., Dimidi, E., Whelan, K. Prebiotics in irritable bowel syndrome and other functional bowel disorders in adults: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2019;109(4):1098-111.

3. Staudacher, H., Lomer, M., Farquharson, F. et al, Diet low in FODMAPs reduces symptoms in patients with irritable bowel syndrome and probiotic restores bifidobacterium species: a randomized controlled trialGastroenterology. 2017;153(4):936-47.

4. Wilson, B., Rossi, M., Parkes, G. et al, OC-026 prebiotic b-galacto-oligosaccharides in conjunction with the low FODMAP diet improves symptoms of irritable bowel syndrome but does not prevent decline of bifidobacteria: a randomised controlled trial. Gut. 2017;66(Suppl 2):A14-A14.

5. Huaman, J.W., Mego, M., Manichanh, C. et al, Effects of prebiotics vs a diet low in FODMAPs in patients with functional gut disorder. Gastroenterology. 2018;155(4):1004-07.

6. Surakka, A., Kajander, K., Rajilic, M. et al, Yoghurt containing galactooligosaccharides facilitates defecation among elderly subjects and selectively increases the number of bifidobacteria. Int J Probiotics Prebiotics. 2009;4(1):65-74.

7. Marteau, P., Jacobs, H., Cazaubiel, M., Signoret, C., Prevel, J.M., Housez, B. Effects of chicory inulin in constipated elderly people: a double-blind controlled trial. Int J Food Sci Nutr. 2011;62(2):164-70.

8. Christodoulides, S., Dimidi, E., Fragkos, K.C. et al, Systematic review with meta-analysis: effect of fibre supplementation on chronic idiopathic constipation in adults. Aliment Pharmacol Ther. 2016;44(2):103-16.

9. Benjamin, J.L., Hedin, C.R., Koutsoumpas, A. et al, Randomised, double-blind, placebo-controlled trial of fructo-oligosaccharides in active Crohn’s disease. Gut. 2011;60(7):923-9.

10. Casellas, F., Borruel, N., Torrejon, A. et al, Oral oligofructose‐enriched inulin supplementation in acute ulcerative colitis is well tolerated and associated with lowered faecal calprotectin. Aliment Pharmacol Ther. 2007;25(9):1061-67.

Conflict of interest disclosures

Dr. Wilson has received a PhD fellowship from Clasado. Dr. Whelan has received research funding from Clasado and Nestle; served as a consultant for Danone; received speakers fees from Yakult; and is the co-inventor of a mobile application for the low FODMAP diet (FoodMaestro).

 
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