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Fiber that Feeds Your Gut Flora

Intestines with and without gut flora

While taking your health into your own hands and learning how to heal your gut, you've probably already read or heard about how important your good bacteria is and the importance of taking a probiotic. Somewhere along the way, you may have come across the importance of fermented foods and feeding your gut flora so that they stay healthy and in turn, you're healthy. To add another layer to this story, you can also keep your healthy bugs happy by eating fresh fruits and vegetables. These foods contain fibers called Fructan and Cellulose, large complex molecules that can't be broken down because humans lack the enzymes to do so. This causes these fibers to stay in the gut and ferment because it's in an environment with, you guessed it, good (hopefully) bacteria. Basically, these fibers serve as "prebiotics."

Prebiotic - "Prebiotics were originally defined in 1995 by Gibson and Roberfroid as “a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health.” 44 and 1

Let's take a closer look

Fructan is a complex "fructose" molecule which is basically the sugar in fruit. This complex molecule and be short or long and is called "fructooligosaccharides." Wow, that's a mouth full! In some of your probiotics you will see an ingredient called, FOS. That's a fructan molecule and in regards to "Fiber"- it's a fermentable fiber in food. This is also known as a "prebiotic." Patients who have SIBO or "small intestinal bacterial overgrowth", can't always tolerate FOS because it feeds the bacteria that lives in the small intestines. Don't worry about understanding SIBO right now. Just know that there's another type of fiber beside soluble and insoluble fiber that feeds your good gut flora and that's Fructan.

Foods rich in Fructans:

  • Bananas

  • Garlic

  • Onions

  • Chicory Root

  • Wheat

  • Leeks

  • Asparagus

  • Artichokes

Cellulose is an interesting fiber we get from eating plant based foods that can also play an important role in feeding our microbiome. The research is less straight forward but basically, each whole food we eat, whether a fruit, vegetable, whole grain, or nut/seed provides different types of fibers. Each species of our gut flora has their own digestive enzymes that recognize and break down various types of fiber, like cellulose. The more diverse our diet, the more diverse our microbiome will be. The more diverse our microbiome, the more protective and health benefits we will receive.

The point

  • Eat a fresh, colorful diet

  • Try a new vegetable to cook with a week.

  • Switch it up. Don't eat the same thing day in and day out. Variety = diversity

  • Consider a Prebiotic-Probiotic combo

Dr. Lexi


44: "Dietary modulation of the human colonic microbiota: updating the concept of prebiotics. Gibson GR, Probert HM, Loo JV, Rastall RA, Roberfroid MB. Nutr Res Rev. 2004 Dec 17 (2): 259-77.

1: Dietary fiber and prebiotics and the gastrointestinal microbiota. Hannah D. Holscher. Gut Microbes. 2017; 8(2): 172-184. 2017 Feb 6. doi: 10.1080/19490976.2017.1290756. PMCID: PMC5390821 PMID: 28165863.

Fiber-Famished Gut Microbes Linked to Poor Health. Katherine Harmon Courage. 23 March 2015. Scientific America.

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