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If you are what you eat, then you are also what your gut bacteria eat: Every time you chow down on a juicy burger or crunch on a kale salad, you’re also passing fuel their way. But just like humans, these microbes don’t all have the same food preferences. Probiotics (a.k.a. the good bacteria in your body), in particular, crave prebiotics, or specific compounds found in a variety of fiber-rich foods. The more of them you consume, the more these beneficial bugs can flourish—which only means good things for you, their generous host.
In fact, that positive effect is in the definition of a prebiotic, which was revised in 2016 by the International Scientific Association for Probiotics and Prebiotics (ISAPP) to be “a substrate that is selectively utilized by host microorganisms conferring a health benefit.” That substance is usually a kind of fiber—because fiber can't be digested well by your stomach, it can make it to your colon largely unscathed, where your probiotics can enjoy it. But science is now discovering that other nutrients, like the polyphenols (a type of antioxidant) in cacao, may also have prebiotic-like effects, Vanessa King, MS, RDN, Honolulu-based registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics, tells SELF.
Once your good gut bacteria get ahold of prebiotics, they can proliferate, which leaves your colon teeming with supportive microbes—and keeps the bad bacteria (their disease-promoting nemeses) at bay, King says. The result? A diverse, balanced microbiome.
Read on to learn all the reasons you should be feeding your gut flora a hefty dose of prebiotic-rich foods, a list of the best ones, and how to work them into your diet.
Why are prebiotics so good for you?
These substances set off a beneficial ripple effect: When probiotics ferment prebiotics, they create short-chain fatty acids (SCFAs), which are important for the health of the cells lining your GI tract, Gail Hecht, MD, Chicago-based gastroenterologist and medical expert at Wonderbelly, tells SELF. When that intestinal barrier is strong, fewer pathogens from your gut can seep through it and infect your body—meaning, your immune system will have less to deal with.
SCFAs might also tamp down inflammation in your gut, which is linked with a lower risk of certain chronic conditions, like type 2 diabetes or cancer. For the same reason, prebiotics may aid in reducing symptoms in folks with inflammatory bowel diseases like Crohn’s and ulcerative colitis.
In the shorter term, eating more prebiotics can also help you poop more regularly and comfortably—again, they’re typically a form of fiber, which helps move things along, Cara Harbstreet, RDN, Kansas City–based registered dietitian and owner of Street Smart Nutrition, tells SELF. In a similar realm, prebiotic-rich foods can keep you feeling full for longer and regulate your blood sugar post-meal, King adds.
How many prebiotics should you aim to eat?
There isn’t a universal dietary guideline for prebiotics (and quantities aren’t labeled on food products), but based on evolving research, ISAPP suggests a target of five grams per day to reap the benefits. For the average person, aiming for the USDA benchmark of roughly 28 grams of fiber a day is an easy way to hit that prebiotic quota (and then some). But it’s worth noting that most Americans are getting roughly half the fiber they should be eating, Harbstreet says, so there’s a good chance you could benefit from some more roughage in your life.
In particular, you might not be eating enough fiber if you’re experiencing abdominal distention (a puffed-out belly even when you haven’t recently eaten) or consistently dealing with bloating and constipation that have no other obvious explanation, Harbstreet says. For most people, an ideal poop schedule looks like one to three bowel movements every one to three days, she adds. That’s a big range, but if you notice a decrease in pooping from your personal baseline, you could be lacking fiber.
Certain health conditions can also affect how many prebiotics you should try to eat, most notably irritable bowel syndrome, King says. The majority of prebiotic-rich foods fall under the FODMAP umbrella, an acronym for carbs that aren’t absorbed well in the small intestine and thus tend to pull water into the gut—which can trigger or worsen IBS symptoms. That doesn’t mean you have to totally avoid prebiotics if you have IBS or another GI condition; it all depends on whether you’re already following a low-FODMAP diet and how your gut responds to individual prebiotic foods, Harbstreet says.
What are the best prebiotic foods?
The cool thing about prebiotics, King says, is that you can get a ton of them from just eating all sorts of plants. And compared to probiotics, she adds, there’s less guesswork in how they’ll affect you: Different probiotics have different effects, so it’s hard to know which strain might serve your gut, whereas prebiotics will help fuel any of the good stuff that’s already in your system.
The abundance of whole foods packed with prebiotics means you can also get plenty of them from your diet and don’t need to reach for a supplement or even a snack with added fiber. Not to mention, eating a whole food means you get the benefits of all the other nutrients it contains too, Julia Zumpano, RD, LD, a registered dietitian with the Center for Human Nutrition at the Cleveland Clinic, tells SELF.
Here are a few of the best food sources of prebiotics—keep in mind that they pack varying amounts (and different types) of the good stuff:
Alliums:
- Onion
- Garlic
- Leeks
- Shallots
- Fennel
Fibrous veggies:
- Asparagus
- Chicory
- Dandelion greens
Root vegetables:
- Sweet potato
- Jerusalem artichoke
- Turnip
Whole grains:
- Oats
- Barley
- Quinoa
Legumes:
- Black beans
- Chickpeas
- Lentils
- Peas
- Edamame
Fruits:
- Banana
- Berries
- Apple
- Avocado
Beyond the above, King notes that there are also a few less-expected sources of prebiotics to look out for, including honey and fermented foods like miso and soy sauce. And as we mentioned, the category of prebiotics is ever-expanding; emerging research suggests that nonfiber substances, like the polyphenols in chocolate, coffee, tea, and some fruits can also play this role in your body.
The best way to add prebiotics to your diet
In a word? Incrementally. Loading up on a ton of prebiotics at once puts you on a fast track toward gas, bloating, cramps, and even diarrhea, Dr. Hecht says. (Remember, these are substances you can’t digest well and that pull liquid into your colon.)
Instead, you want to ramp up slowly and steadily, Zumpano says. A good place to start is having one fruit or vegetable from the above list every time you eat a meal, she says. That might look like having berries or avocado as part of your breakfast, something onion-y or garlicky at lunch, and roasted sweet potato or asparagus with your dinner. Swapping refined grains for whole grains (for instance, white rice for brown, or white bread for wheat) and regularly incorporating legumes into your diet can get your numbers up easily too, she adds. (Might we suggest these creative ideas for chickpeas and black beans?)
And you definitely want to stay well-hydrated as you notch up your prebiotic intake, Harbstreet says. Fiber helps keep you regular by binding with water to push things along, so if you’re low on liquids, that process can’t flow as easily, and you could wind up constipated instead.
But so long as you’re sipping regularly and enjoying the process of trying new foods or recipes (and your gut takes the changes in stride), you’ll only stand to benefit from folding prebiotic-rich foods into your diet—and serving up a veritable feast for your good gut bugs.
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