There are many kinds of fiber—but they are not all created equal as far as your gut bacteria is concerned. Bowlfuls of kale and towers of tomato slices are doing your body good in some ways but your gut flora could care less.
In order to flourish, the bacteria in your colon need a kind of fiber called fructans, which is a type of prebiotic. Experts estimate that the average American only gets about 1 to 4 grams of these fructan-type fibers a day.
Related: 6 Foods to Help You Poop
Gut bacteria also like to feast on cellulose, an insoluble fiber that has been shown to promote good gut microbes. The parts of produce we tend to throw out are high in cellulose—the chewy stalks of broccoli, the fibrous tops of leeks, carrot peels, the bottoms of asparagus—and celery.
How you prepare these foods also matters, since heat breaks down fibers.
Consider the onion—a good source of fructan: the average chain length of fructan in an onion is 26. (The longer the chain length, the more likely the fiber will survive in our gastrointestinal tract.)
Cooking just a little bit breaks the onion fibers down to just 8 or 10 beads. The shorter the chain, the sweeter the food—which is why deliciously sweet caramelized onions retain little fructan fiber benefits.
Here’s a list showing the amount of fructans in a selection of fiberous foods. Start adding fructan-rich foods slowly, particularly if you’ve been eating low on the gut-friendly fiber spectrum. The gradual increase will help you avoid belly bloating and gas.
Related: 5 Ways to Improve Your Gut Flora
|Grams of Fructans*||SUPER|
|47||1 c. Jerusalem artichoke|
|29||1/2 c. chicory root|
|9||1 c. white onions|
|6||1 c. raspberries|
|6||1 c. cooked beans|
|5||5 asparagus spears|
|3||6 cloves garlic|
|1||1/2 c. wheat bran|
|1||1 c. watermelon|
|1||1 medium banana|
|0.7||1 c. blueberries|
|0.7||1 c. broccoli|
|0.3||1 c. kale|
|0.2||2 c. red leaf lettuce|
*Average content of fructans in grams for raw food. Storage, preparation, etc. can affect fructan content.
For ideas on how to get more of these types of stomach-friendly fibers in your diet, here’s a list of simple cooking ideas by Carolyn Malcoun:
1. Toss raw shaved Jerusalem artichokes or asparagus into salads or slaws.
Recipe to Try: Asparagus & Baby Kale Caesar
2. Shred broccoli stems and use in place of cabbage in coleslaw.
Recipe to Try: Broccoli Slaw
3. Rub whole leeks with oil and grill briefly; toss with your favorite vinaigrette.
Recipe to Try: Leek & Lemon Linguine
4. Quickly stir-fry celery with ginger, garlic, soy sauce and peanuts.
Recipe to Try: Stir-Fried Celery with Peanuts
5. Toss artichokes into pasta with marinara sauce, sprinkle on pizza or add to salad.
Recipe to Try: Tomato & Artichoke Gnocchi
For more inspiration, tips and techniques on how to make the most of all your produce, check out Tara Duggan’s Root to Stalk Cooking: The Art of Using the Whole Vegetable (Ten Speed Press, 2013).