Just when you get a handle on all of the health and wellness trends out there, some new concept comes along that brings you back to square one. So you’re probably familiar with probiotics—you’re trying to eat the right gut-healthy foods or taking supplements that contain friendly gut bacteria—but a relatively new product with a similar name may have you all confused.

That’d be prebiotics. Wait, is that just a misspelling of probiotics? Or are prebiotics some kind of wellness snake oil sold by companies who want to ride the coattails of legit probiotics?

And—hold the phone—now there’s buzz about postbiotics?! With all the similar yet different terms swirling around, it’s time to clear up the confusion around what distinguishes each.

What Are Probiotics?

To really understand probiotics’ role in your health, let’s start with a quick refresher of how they work in your digestive tract. Your large intestine (and, to a much lesser extent, your small intestine) is home to an enormous population of bacterial microbes—more than 100 trillion of them.

These trillions of itty-bitty gut bugs have a major impact on your well-being, as a diverse colony of “good” bacteria promotes healthy digestion, while “bad” bacterial strains can cause digestive distress.

But it’s not just smooth bathroom business that makes a thriving intestinal colony so desirable. The microbiome (a term for the sum total of bacteria inhabiting your body) has lately become one of science’s hottest topics, with research linking healthy gut microbes to reduced risks of health conditions, including type 2 diabetes, obesity, Alzheimer’s, heart disease, and even depression.

With all that’s on the line, it’s not shocking that consuming probiotics is becoming the norm. These positive strains of bacteria exist naturally in fermented foods, so you can consume them by eating yogurt, kimchi, kefir, sauerkraut, or tempeh. They can also be encapsulated in pills that deliver a massive dose in one shot—a.k.a. the over-the-counter products most of us think of when we talk about taking probiotics.

So, What Are Prebiotics?

As researchers uncover deeper insights into how probiotics operate, they’ve discovered that there’s more we can do beyond inserting good bacteria into our systems via food or pills.

For probiotics to work most effectively, it’s important to provide them with the best possible environment. (Don’t you want the little buggers to feel right at home in your colon?) That’s where prebiotics come into play.

In the simplest terms, prebiotics are food for probiotics. Your good gut bugs need something to feed on while they’re hanging around your nether regions, and that something is “prebiotic” fiber. This fiber is hardy enough to survive the first several stops along the digestive process (the mouth, esophagus, stomach, and small intestine) and make it to the end of the line (the colon), where probiotics live. Therefore, prebiotic fibers are the so-called “non-digestible” varieties: oligosaccharides, inulin, and fructooligosaccharides.

But you don’t need to memorize that mouthful of nutrition-science vocabulary. Instead, remember that plant-based, high-fiber foods—such as vegetables, fruits, grains, and roots—are good sources of prebiotics. According to the Academy of Nutrition and Dietetics, bananas, onions, garlic, leeks, asparagus, artichokes, soybeans, and whole wheat make some of the best choices.

And What About Postbiotics?!

And now a word about the last type of biotics. Postbiotics, as their name implies, have to do with what happens after digestion. As bacteria “digest” the fibers in your GI tract, this activity produces metabolic compounds. Though in the past, researchers thought of these postbiotics merely as waste byproducts, there’s rising interest in their potential as a medical therapy for inflammatory bowel disease, irritable bowel syndrome, and enterocolitis.

As the research is currently in its infancy, you won’t see postbiotics sold next to prebiotics and probiotics as dietary supplements any time soon. But in a world where nearly anything can be distilled and put in a pill (even fecal transplants!), it’s possible that postbiotic pills will eventually hit the market.

Which Ones Should You Take?

With our biotic terms defined, the question remains: Which of them should you take, and how? If good bacteria benefit us so much, a billions-strong, over-the-counter probiotic supplement may seem like an obvious choice. But as with most health information, it’s not so cut and dry. Two recent studies have raised serious questions around whether probiotic pills actually do what they’re purported to.

In one of the studies, many subjects’ digestive tracts resisted being colonized by probiotic supplements. In the other, taking probiotics to “bounce back” after antibiotics actually proved counterproductive, as doing so made gut flora take longer to return to its “normal” state.

So are probiotics are a bust? What are we to do if we want that all-important healthy gut? “For a generally healthy person, I’d always recommend food first,” says Ali Webster, Ph.D., RD, associate director of nutrition communications with the International Food Information Council Foundation.

“Probiotic supplements have shown benefits only for very specific conditions, like antibiotic-related diarrhea, C. difficile infection, and necrotizing enterocolitis in infants. For other conditions, the evidence isn’t there.” Webster points out that probiotic-rich foods also have “a lot of other beneficial compounds” you won’t get in just a pill, like protein and calcium in yogurt and kefir, or vitamin C in sauerkraut.

As for prebiotics, you don’t necessarily need a pill to keep enough of them in your system, either. And prebiotic-containing foods also boast plenty of important nutrients of their own, so Webster recommends getting them through food as well. However, if your diet doesn’t include many fruits, veggies, or whole grains, or poses certain macronutrient restrictions—(we’re looking at you, keto)—it may be wise to add a prebiotic supplement.

Finally, as with all supplements, if at all possible, talk to a registered dietitian or other health care providers before starting a pre- or probiotic, especially if you have any specific health condition(s), Webster says.