Once you begin learning about your gut, and just how influential it can be to nearly all facets of your health, you'll start to hear a lot of mentions of prebiotics and probiotics. You may even catch references to synbiotics, which you can think of as turbocharged probiotics.
Probiotics, of course, are the "good" live microorganisms that have been hailed as a potential antidote for a variety of health ills, says Kelly Scott Swanson, PhD, professor of animal and nutritional sciences at the University of Illinois at Urbana-Champaign.
Synbiotics combine probiotics with prebiotics, which are a type of fiber that feed friendly gut bacteria. "Simply put, prebiotics must be available for the probiotics to thrive," says Sharon Zarabi, RD, bariatric program director at Lenox Hill Hospital in New York City.
"Ideally, the synbiotic formulation should have more of a health effect than each of the components alone," says Andrea Azcarate-Peril, PhD, associate professor of medicine and nutrition at the University of North Carolina at Chapel Hill.
What Synbiotics Do in the Body
Synbiotics improve the composition of bacteria in your gut by stimulating the growth of certain friendly bacteria, explains Alicia Romano, RD, a spokesperson for the Academy of Nutrition and Dietetics.
Adding prebiotics to probiotics is also supposed to help the probiotics survive as they travel through the tricky upper intestinal track to their ultimate destination, which is the colon, according to a December 2015 review in the Journal of Food Science and Technology.
"There are different ways they can function, but in the end you're trying to target the gut and/or target some of other tissues working through the gut," Swanson says.
Many of the effects can be seen in immunity, allergy and inflammation. "One of the key mechanisms of both probiotics and synbiotics is strengthening the gut barrier and strengthening the immune system," Swanson adds.
Potential Health Benefits of Synbiotics
The research into the potential benefits of synbiotics is still developing. But the same benefits attributed to probiotics logically can be attributed to synbiotics, as well. Namely, they help promote the good bacteria in your colon, which may benefit metabolic health and the immune system.
Different studies have found effects with everything from diarrhea to liver function, obesity and type 2 diabetes, per the Journal of Food Science and Technology review. There are even papers suggesting that synbiotics (and probiotics) can prevent surgical infections and sepsis, according to a June 2020 study in the Annals of Surgery.
The strongest evidence for probiotics (which have been more extensively researched than synbiotics) supports prevention and treatment of diarrhea, especially in children, Azcarate-Peril says. That includes cutting the duration of bouts of traveler's diarrhea.
How to Get Synbiotics Through Your Diet
But that doesn't mean any synbiotic or probiotic will do.
A healthy diet is the best way to get synbiotics into your system. "Not only will they provide these beneficial microorganisms, but also a host of other key nutrients for general health," Romano says.
Foods high in prebiotics include garlic, onion, slightly green bananas and Jerusalem artichokes, she says.
Probiotic-rich foods include fermented foods like yogurt, kefir, tempeh, miso, sauerkraut, kimchi and some aged cheeses. Others sources include soybeans, raw oats, unrefined barley and unrefined wheat, per the Journal of Food Science and Technology review.
"Your first line of defense to a healthy gut should always be food."
To get both prebiotics and probiotics in your system, Romano suggests a bowl of yogurt and kefir topped with a slightly green banana; marinated tempeh served with asparagus and artichokes or stir fried with kimchi; or yogurt dip with grated garlic and onion. Kombucha, too, could be a way to get synbiotics, Azcarate-Peril says.
What to Know About Synbiotic Supplements
Synbiotic supplements are certainly available on grocery store and pharmacy shelves, but that doesn't mean they'll be helpful.
"Your first line of defense to a healthy gut should always be food," Zarabi says. "If for any reason the combination of foods above does not work in your favor, [supplements] can be considered."
Picking a supplement can be a thorny issue. Nutritional supplements aren't regulated like prescription drugs and they're not as well researched, meaning you can't guarantee that you're actually buying a product that is synbiotic and effective, Romano cautions.
Plus, prebiotics, probiotics and synbiotics aren't one thing. There are tons of strains out there that can be combined in any number of ways. If you have a gastrointestinal issue and are interested in synbiotics, Romano suggests talking with your doctor or registered dietitian.
"The research is definitely still developing," she says. "Right now, the area of gastrointestinal health and the gut microbiome is an exciting area of research, with a lot left to learn."