Probiotics, prebiotics — now postbiotics? What's known and not about latest gut research

Probiotics have been all the rage the last few years, as more food companies advertised the active bacteria in their products and consumers became more aware of the role of bacteria in keeping their gut healthy. 

Also in the "biotics" family is prebiotics, the stuff that probiotics eat, such as high-fibre foods.

Postbiotics is a less familiar term, but one some microbiologists say is a huge area of interest.

"Understanding what the microbiota is and how it changes in disease, that was a huge deal five years ago," said Lisa Osborne, an assistant professor in University of British Columbia's microbiology and immunology department. 

"Then we realized maybe it's not necessarily who's there but what they're doing, the postbiotics that are being produced and how that's influencing the host's post-response. It's still a relatively new field."

Postbiotics are the waste left behind after your body digests probiotics and prebiotics. Some postbiotics are the product of fermentation and some postbiotics are the structural parts of the cells themselves. 

They can be found in fermented foods, but your gut can also make them, Jennifer Stearns, a microbiologist and assistant professor in McMaster University's department of medicine, told Dr. Brian Goldman, host of CBC's The Dose. 

Although an official definition of postbiotics has been decided by experts only within the last year, researchers have been well aware of postbiotics in the human gut for several years.  

"People are trying to figure out how to improve their gut health in order to improve their overall health. And postbiotics are just part of that conversation," Stearns.

Yet, even if the term is already popping up on commercial supplements, there are still many unknowns when it comes to postbiotics and any potential health benefits, Stearns said. 

What are they?

Last year,  a group of experts from around the world specializing in nutrition, microbiology, food science and other research areas came to a consensus on the definition of postbiotics. 

The panel organized by The International Scientific Association of Probiotics and Prebiotics (ISAPP) agreed a postbiotic is a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host."

Most people will get postbiotics from fermented foods like kefir or kimchi. 

"When you eat fermented foods, then you're getting all of it. You're getting the prebiotic, the probiotic and the postbiotic. It's the super mix," Stearns added.

Postbiotics can also come in the form of an oral supplement that can be purchased online. But most Canadians won't have easy access to them on store shelves, some experts say, and warn against purchasing them in oral supplement form. 

"It's still so new that it's not something that I would recommend, even if you could find it at a health food store," said Osborne.

Health Canada has not approved any natural health products with postbiotics as the "recommended use or purpose," a spokesperson said. 

Postbiotics are also becoming more popular in the skincare industry, which is largely focusing on the skin's microbiome. 

Identified as a top trend by WGSN, a global source for trend forecasting, the next evolution of beauty inspiration from Korea and Japan will put fermented ingredients in the spotlight. 

Are there proven health benefits to postbiotics?

The gut's microbiota (also known as microorganisms) and its relationship to overall health is a major area of research. 

Researchers are trying to get a better understanding of the gut-brain connection and what a "healthy" gut microbiome looks like. 

Often dubbed the "second brain," the enteric nervous system (ENS) found within the digestive system has been shown to have effects on our moods and brain health.

A clinical study recently published in the peer-reviewed Journal of the American Medical Association, for example, found a highly pure supplement of urolithin A — a gut microbiome postbiotic — may improve muscle endurance in older adults. 

Another possible postbiotic, butyrate, a short-chain fatty acid, has been shown in some cases to reduce inflammation, said Andrea Azcarate-Peril, a microbiologist and associate professor at University of North Carolina at Chapel Hill's department of medicine and nutrition.

A 2009 study published in the peer-reviewed journal Diabetes also found that dietary supplementation of butyrate can "prevent and treat diet-induced insulin resistance" and obesity in mice that were on a high-fat diet.

But Stearns warns the oral supplement hasn't been tested extensively in humans for weight loss.

Although ISAPP doesn't technically recognize butyrate as a postbiotic, some of the researchers who spoke to CBC did.

Postbiotics could also prevent common infectious diseases like upper respiratory tract infections and acute gastroenteritis, but more clinical trials are still needed, according to one of the experts involved in crafting the definition of postbiotics.

What don't we know about postbiotics?

Azcarate-Peril said more needs to be done to get a better understanding of how postbiotics may help reduce inflammation and other health concerns — or if  they can't help at all. 

"There's enough knowledge to be more specific" in the research questions asked, she said. 

Stearns said one of the reasons postbiotics are an interesting area of research is because they are "emerging as a safer alternative" to probiotics. 

Probiotics are live organisms and there may be a small risk of infection if given to those who are immunocompromised, she said. Since postbiotics are dead bacteria, there is potential they may be safer for some, adding more research to figure out their potential is needed. 

It's also still unknown how effective an oral postbiotic can be for someone's health and for specific health conditions, said Stearns. 

She said for now, eating fermented foods is an easier way to get "the desirable effect of probiotic and postbiotic organisms."

Produced and written by Stephanie Dubois