You know fiber is important—after all, when you don’t get enough of it your pipes can get, well, clogged. But fiber does more than just keep you regular. One type of fiber, known as prebiotic fiber, also feeds probiotics, the healthy bacteria found in your gut.
“The more food, or prebiotics, that probiotics have to eat, the more efficiently these live bacteria work and the healthier your gut will be,” says New York City-based nutritionist Vanessa Rissetto, R.D.
Prebiotic fiber is insoluble, meaning it passes through your GI tract virtually undigested until it reaches your colon, where it provides nutrients to the healthy bacteria there.
“Research has actually shown that prebiotics can change the microbiota of the digestive system for the better, which leads to a wide range of health benefits,” says Josh Axe, D.N.M., C.N.S., D.C., founder of DrAxe.com, best-selling author of Eat Dirt, and co-founder of Ancient Nutrition. “Since gut health is so closely linked to so many other bodily functions, both prebiotics and probiotics are crucial.” In combination with a healthy population of probiotics, prebiotics help boost nutrient absorption and keep our immune system functioning at its best.
To feed your probiotics the good stuff they need, you’ll want to chow down on foods high in that insoluble fiber—so we asked the experts to share the top five prebiotic foods—along with how to add them to your diet.
Keep in mind that foods generally contain more prebiotic fiber raw than they do cooked, since they have higher overall fiber content (and thus higher prebiotic content) when raw, says Axe.
Try to incorporate several of these prebiotic foods into your diet every day for optimal gut-lovin’ goodness. (If any are no-go’s or life gets in the way of your healthy eating habits, consider an insoluble fiber supplement to feed your good gut bugs.)
1. Raw Dandelion Greens
This bitter, crunchy green is 24.3 percent insoluble fiber by weight and offers a good dose of prebiotics, says Sydney Zivertz, health and nutrition investigator for ConsumerSafety.org. Besides being a top source of prebiotics, “dandelion greens are also rich in vitamin K, which helps our blood clot properly and supports bone health,” says Axe.
Try tossing dandelion greens (you can find ‘em at most health food stores) into your next salad. The smooth, mild flavor of tomatoes and olive oil offer a nice contrast to the bitterness of raw dandelion greens.
2. Raw Garlic
Your favorite seasoning is another one of the best sources of prebiotic fiber out there, clocking in at 17.5 percent insoluble fiber by weight, says Zivertz. Not only does garlic add great flavor to food, but it’s also loaded with nutrients, including vitamin B6 and vitamin C, says Tanya Zuckerbrot R.D., founder of The F-Factor Diet. It also has powerful antioxidant properties and contains ‘organosulfur’ compounds that support heart, liver, and immune health.
Try adding minced raw garlic to soups (Zivertz likes sprinkling it into chili) and salad dressings.
3. Raw Onion
The next time you build yourself a sandwich or salad, don’t forget to add some raw onion, which is 8.6 percent insoluble fiber by weight. This source of prebiotics also contains the antioxidants vitamin C and quercetin, which fight off free radicals and cell damage, along with chromium, which supports insulin function, says Rissetto. “Since most of the flavonoids [the compounds responsible for onions’ health benefits] are found in their outermost layers, peel off as little as possible before chopping, dicing, and tearing,” she suggests.
4. Raw Asparagus
At five percent insoluble fiber by weight, raw asparagus is another nutritious source of prebiotic fiber. It also contains a number of antioxidants, which boosts its gut and immune benefits, says Zuckerbrot.
Since eating raw asparagus is less than appealing, Zuckerbrot recommends fermenting (a.k.a. pickling) it to munch on as a snack or side dish. (Intrigued? Try this recipe.)
5. Whole-Wheat Flour
Last but not least: whole-wheat flour, which comes in at 4.8 percent insoluble fiber by weight. Whole grains also contain magnesium (a mineral that helps your muscles function properly), vitamin E (an antioxidant), and selenium (a mineral that helps keep your thyroid in check).
Look for flours, cereals, breads, and other baked goods labeled ‘100-percent whole-wheat.’