Gut health is all the rage. From fermented drinks like kombucha to high-fiber diets, nutritionists and researchers alike have zeroed in on the gut microbiome as a compass for a person’s overall health.

As a result, probiotics, also known as beneficial gut bacteria, are experiencing a renaissance. Now their closely named peer, prebiotics, is also gaining traction as one of the latest darlings in gut health.

What’s the difference? While probiotics are themselves gut bacteria, prebiotics are the food that feeds bacteria. Prebiotics resist digestion in the small intestine and, upon reaching the colon, are fermented by bacteria in the gut. When you think about prebiotics, you should be thinking about fiber.

“The human body can’t break down certain plant fibers—prebiotics—but probiotics can,” says Debbie Petitpain, a registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics. “In the process, the friendly gut bacteria make these plant fibers easier for the human body to eliminate, and in return, they get the nutrients they need to thrive.”

While there’s been a lot of fuss over the importance of probiotics, prebiotics are critical when it comes to maintaining gut microbiome health. “There are literally thousands of types of bacteria that live in the gut, and they don’t all survive off the same nutrients,” Petitpain says. “Prebiotics, therefore, influence the growth of some bacteria over others and can influence the overall gut microbiome or the complex community of microorganisms that live in the digestive tract.”

“Prebiotic supplements are out there, but they’re not necessary.”

Prebiotics have also been studied for a wide range of other health benefits, including lowering blood pressure, reducing the risk of coronary heart disease, fighting mental illness, and even improving vaginal “ecosystem” health.

The good news is that sources for prebiotics are widely available. Complex carbohydrates that include nondigestible fibers are natural sources of prebiotics. This includes fruits, vegetables, and whole grains, Petitpain says, especially foods like bananas, onions, garlic, leeks, asparagus, artichokes, and soybeans.

You can also find prebiotics in many “added fiber” foods. Inulin, a soluble fiber from chicory root, is a common prebiotic used to fortify many protein bars and cereals. But if you have a balanced diet, you should be getting all the prebiotics you need without the need to supplement, particularly when it comes to fiber.

“Prebiotic supplements are out there, but they’re not necessary,” says Wesley Delbridge, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. “However, most Americans do not get the recommended 25 to 35 grams of fiber per day.”

If you choose to try a prebiotic supplement, it can be tough to determine just how much you should take. That’s because research on the ideal dosage needed to gain health benefits is still ongoing. Many research studies will use a dose of prebiotics between two and 10 grams. That’s key to keep in mind, because getting too many prebiotics can have some unpleasant side effects.

“Gut bacteria only needs so much food,” Delbridge says. “If it’s being fed too many prebiotics, the rest will just be excreted.”

The bottom line is that while you likely don’t need to be supplementing your diet with prebiotics, especially if you eat a well-rounded diet that’s rich in fiber, the worst that can happen is an upset stomach.