Leading international scientists advance a new definition of synbiotics

Reviewed by Emily Henderson, B.Sc.Aug 21 2020

The word 'synbiotic' appears on a growing number of food and supplement products, with synbiotic ingredients showing promise for modulating the community of microbes living in the human gut, while providing a health benefit. Synbiotics are generally understood to be a combination of a probiotic and a prebiotic--but experts have deemed this description too limiting for innovation in this field and too ambiguous to allow for a clear understanding of synbiotic health benefits.

To address the scientific ambiguity around synbiotics, a group of 11 leading international scientists formed a panel to create a consensus definition and to clarify the evidence required to show synbiotics are safe and effective.

In a paper published in Nature Reviews Gastroenterology & Hepatology, the authors advance a new definition of synbiotics, which is informed by the latest scientific developments in the field: "a mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host".

The experts on the panel emphasize that the definition is designed to be inclusive--many different combinations of live microorganisms and selectively utilized substrates could qualify as synbiotics, as long as a human study demonstrates the health benefits of any particular combination. Furthermore, synbiotics need not be limited to the gut; they could potentially target any part of the human body that harbours a community of microorganisms.

We hope the publication of this definition will mark a shift in people's understanding of synbiotics. We can begin discussing synbiotics in a more scientifically accurate way, giving everyone a shared vocabulary for understanding what they do, how they work, and what evidence is needed to meet the definition."

Kelly Swanson, First Author, Professor in the Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois at Urbana-Champaign

In the publication, the group also makes a distinction between 'complementary synbiotics', in which a probiotic and prebiotic are combined but work separately, and 'synergistic synbiotics', in which the selectively utilized substrate specifically feeds the microorganisms that accompany it.

The expert panel was convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP), the non-profit organization that previously led the scientific consensus definitions of both probiotics and prebiotics.

"Creating a definition of synbiotic is a first step," says Mary Ellen Sanders, ISAPP's Executive Science Officer. "From here, the scientific community can focus on designing and carrying out studies to test the health effects of these products."

Surveys indicate that consumers increasingly look for evidence that products on the market provide the benefits they claim to provide. Sanders says, "We expect that the scientific data on synbiotic health benefits will increase over time, alongside an increase in general awareness about synbiotics."