Urbana, IL—An international panel of experts, including two from the University of Illinois, has redefined the termsynbioticsand developed guidelines on the scientific investigation thereof, according to a press release. The consensus report, written by the International Scientific Association for Probiotics and Prebiotics (ISAPP), has been published inNature Reviews: Gastroenterology & Hepatology.

"Synbiotics are starting to gain traction in the marketplace, but there's a lot of confusion around the term, even among scientists," says Kelly Swanson, consensus panel chair and professor in the Department of Animal Sciences at Illinois, in the press release. "The panel's main goal was to clarify what synbiotics are and provide guidance for future research and innovation."

The general idea of synbiotics—thus far, known as a combination of prebiotics and probiotics—was first proposed in 1995 when prebiotics were defined, the press release explains. But FDA has never defined the concept, which has therefore been left open to interpretation.

"This consensus statement provides guidance for different stakeholders, including scientists in academia and industry, consumers, and even journalists. We want to remind each group that these terms should be used consistently, avoiding sensationalizing or overstating health claims," says Hannah Holscher, panel member and assistant professor in the Department of Food Science and Human Nutrition at Illinois, in the press release.

The new definition: “A mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host.”

The definition doesn’t contain the words “probiotics” and “prebiotics”—and this is for a reason, the press release says. “The old definition of synbiotic,” which included pre- and probiotics, “may have restricted innovation,” Holscher suggests. Omitting these terms allows for the use of micoorganisms and selectively utilized substrates that may work together to elicit a health benefit, even if they don’t fit the definitions of pre- and probiotics when administered independently.

Moreover, the definition doesn’t require synergy. A probiotic could boost immunity while a prebiotic aids in digestive health; the goal may not be the same, but as long as they provide those benefits to a host while in use together, they’re still complementary synbiotics.

"The key there is testing. Even if the pre- and probiotics work separately, there could be some antagonism when put together. So really, they need be tested together in the target animal or human. We don't want companies just randomly throwing things together," Swanson says in the press release.
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This isn’t to say that synergistic synbiotics don't exist. Holscher explains: “In synergistic synbiotics, the substrate would support probiotic survival. For example, providing an energy source for the probiotic or changing the microbiome to support the survival of the probiotic.” These additive synbiotics, the press release says, are most likely to be made with novel ingredients not already categorized under the current definitions of pre- and probiotics.

Either way, the panel of researchers emphasizes the importance of testing the ingredients together. The report lays out testing protocols for multiple hosts.

And when these products make their way to consumers, Holscher and Swanson have some advice.

"The question is not whether you should take a pre-, pro-, or synbiotic,” Holscher emphasizes. “The question is, 'what do you need those products to do?' We know a lot about the specific health outcomes of these products, so it's a matter of finding what you need rather than thinking of them as a blanket cure-all."

"Just because there's a pre-, pro-, or synbiotic on the market, that doesn't mean they'll work across the board from infants to adults to geriatrics, from heart disease to gastrointestinal health,” Swanson agrees. “They're all really there for a specific purpose.”