Probiotics are microorganisms found in yogurt and other fermented foods that promote the spread of healthy bacteria in the body.
Good bacteria can help with digestion, destroy disease-causing cells or produce vitamins that are beneficial for everyday health, according to the National Center for Complementary and Integrative Health (NCCIH).
Many proponents of probiotics claim they aid digestion, promote gut health and may help prevent certain illnesses. While probiotics have been a health trend for years, there's still a lot to learn about these microorganisms and their various bacteria strains — and a lot of confusion over related products and supplements. The microbiome — the community of bacteria that live on and in our bodies — is still a mystery in many ways, but here is what we do know.
The research is promising. Probiotics have been used to help prevent diarrhea associated with using antibiotics, and to prevent sepsis and necrotizing enterocolitis in premature babies, according to the NCCIH.
Probiotics may also be beneficial for people who have ulcerative colitis. (Much of the research on probiotics has focused on gastrointestinal issues.)
There are other health conditions that may benefit from probiotics, too. Researchers have studied how they could potentially help people who have tooth decay, gum disease, allergies, acne and more. One NBC reporter even participated in a clinical study to see if a probiotic spray could ease her eczema. (It didn't, but some of the other study participants found relief.)
However, there are multiple types of probiotics, and researchers are still figuring out which bacteria strains help which conditions — and how much of the probiotic someone would need to see a benefit. Until that's better understood, using probiotics to treat a particular condition is basically a gamble.
"Everybody has trillions of bacteria in their bodies," said Marion Nestle, a professor of nutrition at New York University. "It's only within the last 10 years or so that scientists have been able to categorize the bacteria. That’s when the explosion of interest started in the microbiome, because all of a sudden, you could measure it. But no one really knows what any of it means."
Where do probiotics come from?
Yogurt is probably the most common food source of probiotics, but they can also be found in kombucha, kimchi, sauerkraut and pickles.
If those foods aren't part of your everyday diet, you're not alone.
"I think that is one of the problems," said Samantha Cassetty, a registered dietitian based in New York City. "Aside from yogurt, most people's diets are going to be pretty limited (when it comes to probiotic food sources)."
That may be why some people turn to supplements. In fact, the market for probiotic supplements is hugely popular. But experts warn that consumers should be cautious. Many probiotics are sold as dietary supplements, which aren't regulated by the U.S. Food and Drug Administration. And since the science is still emerging, consumers won't always know if the strain, or strains, that they're taking will produce their desired benefit.
"The issue is that with probiotics, to treat something you need a specific strain that has been tied to a specific benefit in a specific dose," Cassetty said.
If people still want to experiment with probiotic supplements for overall health, Cassetty recommends they choose one that includes a variety of strains.
"What is exciting about probiotics is that, I think, one day we're going to be able to get very specific and personalize nutrition — and start recommending species and strains to address a whole spectrum of health problems, depending on what the person individually needs," she said. "But right now, we're just not quite there yet."
What about prebiotics?
You may have also heard of prebiotics, which are a type of fiber that feed the community of microorganisms in your gut. In other words, they're food for the probiotics.
Prebiotics are found in certain fruits, vegetables and whole grains. Antioxidants, including those from berries and nuts, are also important to feed the good bacteria.
Basically, a healthy diet is key. Both Cassetty and Nestle emphasize that if people eat the right foods, health benefits will follow — and they won’t really have to worry so much about what’s going on in their microbiome.
If you do want to make sure you’re getting your dose of probiotics, a serving of yogurt a day is a good place to start. Just be sure to check the yogurt label to make sure it contains "live and active cultures."
And get the sugar-free kind, Nestle advised. “Add your own sugar — you’ll be putting a lot less in!” she said. Or better yet, use fresh fruit to help sweeten it up.