No one enjoys being gassy, crampy, or bloated, but there’s so much more to gut health than avoiding toxic fumes or accepting the reality of frustrating bathroom emergencies. In fact, our gastrointestinal (GI) health (or lack thereof) has a significant impact on our immune function and our body’s ability to fight off harmful organisms and substances.

So how does it all work? Much of the digestive tract (70 percent, to be exact) is made up of tissue that basically acts like a screen, filtering through the substances that are safe to enter the bloodstream and shuttling others out of the body, says Brian Tanzer, M.S., nutritionist and manager of scientific affairs for The Vitamin Shoppe.

A healthy, balanced diet plays a huge role in a properly-running gut, but supplements can also help keep your system balanced. But, uh, which type do you need? Should you take more than one? In a search for digestive supps, you’ll come across the three major players: probiotics, fiber, and digestive enzymes. Consider this your handy guide.

Probiotics

We know you’ve seen yogurt commercials promoting the ‘healthy bacteria known as probiotics. And according to Tanzer, fermented foods like kimchi or yogurt should be your primary source of probiotics, since they support your digestive system and promote regularity. (Fermented foods have been produced or stored so that certain bacteria in them can flourish. Veggies like cabbage are stored in a jar of salty brine to make kimchi, while bacteria are added to milk and then strained to make yogurt.)

Related: 5 Foods That Are Packed With Probiotics

Your GI tract is also home to harmful bacteria, so you need probiotics to maintain balance, says Tanzer. There are plenty of reasons you might not be counteracting those bad guys, though: If you don’t eat probiotic-filled foods, just finished a round of antibiotics (which kill off both good and bad bacteria), or have yeast overgrowth(you know the struggle, ladies), you may want to consider a probiotic supplement.

There are many different strains of probiotics, and you’ve probably heard of a few, like acidophilous and lactobacillus—so look for a supplement that contains a variety. If you’re coming off a course of antibiotics, a supplement with a high probiotic count (like 50 billion) may help to repopulate those healthy bacteria faster. But if you’re supplementing long-term, don’t worry about finding the highest-potency bottle, Tanzer says.

Fiber

Probiotics do rely on one thing in order to keep your gut in tip-top shape, though: fiber. “These bacteria feed off of fiber, so taking probiotics, but not getting ample fiber, is like planting grass seed but never watering it,” says Tanzer. Many probiotic formulas contain a type of fiber called prebiotics, but a diet high in fiber and low in processed foods will best keep those good bacteria flourishing. So, if your nutrition is sub-par, though, you may need to couple that probiotic supplement with additional fiber.

Not only does fiber provide food for probiotics, it also helps keep your toilet time regular and supports healthy blood sugar and cholesterol levels. But not all fibers are created equal.

Insoluble fiber like oat bran, which we can’t digest, passes through the GI system. On its way, it attracts water, expands, and causes muscle contractions, helping you to go number-two, says Tanzer. Soluble fiber, on the other hand, becomes gel-like when digested and binds to carbohydrates and cholesterol, slowing their absorption into the bloodstream. Your body needs both types of fiber!

Related: 7 Possible Reasons Why You Just Can’t Poop

If you don’t eat many whole foods like fruits, vegetables, and whole grains, or if you deal with constipation and irregularity, chances are you may not be getting enough fiber. (The USDA recommends 25 grams a day for women and 38 for men.)

If your fiber concerns are mainly bathroom-related, look for an insoluble fiber supplement like oat bran. For blood sugar and cholesterol support, go for soluble fiber like psyllium or apple pectin.

Keep in mind that fiber needs water to keep it moving through the intestinal tract, so it’s important to stay well-hydrated if you’re taking a fiber supplement, says Tanzer. Otherwise you may just end where you started: constipated.

Digestive Enzymes

You’ve probably already heard something or other about probiotics, fiber, and your gut—but digestive enzymes may seem a little more…exotic? Here’s the deal: “The body produces a number of enzymes that help you break down different foods and absorb nutrients as they move through the digestive tract,” says Tanzer. For example, the enzymes protease and peptidase break proteins down into amino acids.

But it’s not that simple! Factors like food intolerance, age, and certain medications can affect our enzyme production as well as our body’s ability to break down various foods and absorb their nutrients.

People taking medications for acid reflex or indigestion, specifically proton pump inhibitors (PPIs), may want to consider taking a general digestive enzyme supplement since these meds lower stomach acid production and can mess with our ability to digest food, says Tanzer.

As we get older, the body produces fewer enzymes and the lining of our GI tract can begin to atrophy, so people over age 60 may also want to supplement with digestive enzymes.

Most digestive enzyme supplements contain a combo of different enzymes so that they’re effective on  different types of foods, says Tanzer, though you can find specific types of enzymes, too. Individual enzyme supplements can be particularly beneficial for people with food intolerances, such as lactase for the dairy intolerant and specific proteases for the gluten intolerant.

Pin this handy infographic to help keep your gut health on lockdown: