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Can prebiotics help tackle obesity? New systematic review questions available evidence, draws criticism

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Adi Menayang

By Adi Menayang

05-Sep-2017
Last updated on 06-Sep-2017 at 12:26 GMT2017-09-06T12:26:01Z

Photo: iStock/Hannah Gleg
Photo: iStock/Hannah Gleg

In a systematic review, researchers in Brazil concluded that with the science available, “it would not be appropriate to recommend, at the moment”, the clinical use of prebiotics, or its combination with probiotics, to tackle obesity-related health risks.

“Some prebiotics and synbiotics may have immunomodulatory action, however, more randomized controlled trials are needed to support the clinical use of inulin-type fructans, galacto-oligosaccharides or related synbiotics,” they wrote in their study, published in the journal Clinical Nutrition.

Led by Dr Erasmo Trindade of the Federal University of Santa Catarina in Brazil, the researchers pooled together 10 randomized controlled trials that investigated the use of prebiotics and synbiotics, which modulate intestinal bacteria, in improving metabolic and immune functions of overweight and obese populations.

According to the researchers, no systematic review has been conducted on the effect of popular prebiotics such as inulin-type fructans and galacto-oligosaccharides on metabolic and immune functions.

One expert criticizes the ‘lump’ of prebiotics analyzed

Aside from narrowing the study population to obese and overweight individuals, the researchers narrowed down the intervention product by searching for existing studies using the terms ‘prebiotic,’ ‘fructan,’ ‘fructooligosaccharide,’ ‘inulin,’ ‘galactooligosaccharide,’ ‘synbiotic,’ ‘bifidobacter-,’ and ‘lactobacil-.’

This diverse set of intervention search terms drew some criticism. They have lumped together studies that include inulin, FOS, and GOS, and synbiotic trials that use different probiotics,” said Dr Brad Saville, commenting independently on the study.

Dr Saville is a professor of chemical engineering and applied chemistry at the University of Toronto, and Chief Science Officer at Prenexus Health, which manufactures the prebiotics ingredient XOS95.

“The authors then go on to say that they cannot do a meta-analysis because this small set of trials had material differences, including the fact that they used different prebiotics (and/or doses), and different probiotics with the prebiotic. Yet, that is how they designed their search!” Saville added.

“I could have told them up front that they should not do a meta-analysis based upon their chosen search criteria, although perhaps they were hoping to find more papers than were realistically available, and they may have been hoping to compare different prebiotics.”

A more optimistic result

Saville admitted that the study offered some ‘excellent commentary; about the design of clinical trials that involve prebiotics and synbiotics, “information that would be very useful for companies producting/marketing probiotics, prebiotics, and synbiotics as they plan clinical trials with their products.”

The study addresses a popular area of microbial science, “namely dietary modification of the gut microbiota,” Prof Glenn Gibson, who teaches food microbial sciences at the University of Reading, told NutraIngredients-USA. Prof Gibson coined the term ‘prebiotic’ in a 1995 paper.

However, both Saville and Gibson would have extracted a different conclusion from the systematic review. “Given the lack of side effects, including low calorific influences, and safety profile of prebiotics, I would be a little more optimistic than the review suggests and conclude that they could be recommended for such situations,” Gibson said.

For Saville, the Brazilian researchers’ conclusion was unfair. “The fairest conclusion would be to state that there are not enough studies with specific prebiotics (or synbiotics) to reach a firm conclusion regarding efficacy or clinical application,” he said.

“Instead, because the trials selected are materially different, and they cannot do a meta-analysis, they state that ‘it would not be appropriate to recommend, at the moment, the clinical use of these food compounds...’”

“That is a materially different conclusion and implication regrading the potential efficacy of prebiotics or synbiotics; to a certain extent, the conclusion is driven by their methodology, rather than an outright acknowledgement that there are simply not enough studies with a particular prebiotic/synbiotic to do an analysis.”

Source: Clinical Nutrition
Published online ahead of print, https://doi.org/10.1016/j.clnu.2016.10.003
"Effects of inulin-type fructans, galacto-oligosaccharides and related synbiotics on inflammatory markers in adult patients with overweight or obesity: A systematic review"
Authors: R. Fernandes, et al. 

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