Prebiotics: Beneficial bacteria’s best supporters
If ‘probiotics’ were an athlete, she would be the star of the track team. She would be the one getting all the gold medals, receiving the armfuls of flowers, and appearing in the magazine ads. She's talented, and everyone knows it.
But it wouldn't be fair to give all the credit to probiotics, when her teammate ‘prebiotics’ has worked so hard to help probiotics shine. Prebiotics has given probiotics the prime starting lanes, has let her take centre stage in the TV interviews, and has been there with hugs and high fives on all of the toughest days. Probiotics wouldn't be where she is without her loyal teammate giving her the best advantages.
When it comes to gut health, probiotics and prebiotics are teammates that share their success. That is to say, while beneficial bacteria like Bifidobacterium species may ultimately be responsible for many positive effects on human health, it’s the prebiotics that allow these bacteria to thrive in the gut environment.
A large body of scientific research shows that certain bacteria have the ability to positively affect our health. An official definition of probiotics has existed since 2001, when a group of scientists (members of the International Scientific Association for Probiotics and Prebiotics, or ISAPP) described probiotics as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host". So in order to be called a probiotic, a species or strain of bacteria must be scientifically tested and shown to have a specific effect on health. It doesn’t really matter how the bacteria achieve this effect, as long as the effect can be demonstrated. (In fact, probiotics are unlikely to stick around in the digestive tract when taken as supplements or consumed in specific quantities through foods like yogurt.)
Prebiotics, on the other hand, necessarily play a role that supports beneficial microorganisms and allows them to do their work. But for the past twenty years or so, groups around the world had slightly different ideas about what fell into the prebiotic category; some insisted a prebiotic substance had to be something that specifically boosted populations of bifidobacteria and lactobacilli, since these bacteria were widely known to be beneficial. Others disagreed, saying that growing evidence on the human microbiome shows a wide range of bacteria besides bifidobacteria and lactobacilli can contribute to health.
Earlier this year, when ISAPP published their new consensus statement on the definition of prebiotics, the more inclusive concept won out. Prebiotics are now defined as "a substrate that is selectively utilized by host microorganisms conferring a health benefit". Thus, a prebiotic substance, rather than being metabolized by the human body, is metabolized by bacteria in the digestive tract—and furthermore, it’s the use of the prebiotic by bacteria that is responsible for the positive health effect. Substances like inulin, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS), are historically the most well-studied prebiotics, but other important substances such as digestion resistant starch (DRS) also fit the category.
Another point made in this consensus statement is that a prebiotic can be any substance that induces a health effect by modulating the microbial community, whether it’s in the gut or in the mouth or anywhere else in the body. So in the years to come, prebiotics will likely expand beyond the special forms of dietary fiber that are popularly known.
As solidified by the new definition, prebiotics come with built-in probiotics since they necessarily stimulate the growth of beneficial microorganisms already living in the gut. In many situations, however, health professionals recommend consuming both probiotics and prebiotics in parallel. Depending on the exact probiotic and prebiotic taken, the prebiotic may serve to increase populations of the same microorganisms contained in the probiotic supplement, or it may affect different beneficial microorganisms altogether.
As any successful person knows, no one can shine without someone there to support them. It’s true in the gut as well—although prebiotics don’t always get the spotlight, they’re the expert supporters of the beneficial microorganisms that do such important things for our health.
Kristina Campbell is a science writer specializing in the gut microbiota, diet, and digestive health; she is author of The Well-Fed Microbiome Cookbook. Find her on Twitter: @bykriscampbell