Functional MedicineNutrition

Prebiotics: What are they and Why are they important?

We hear about probiotics, the “good bugs” in our digestive system a lot, but what’s all of the buzz about prebiotics?

Prebiotics are the fiber-rich foods that probiotics feed on. Taking probiotic supplements or consuming probiotic rich foods such as kefir, yogurt, kimchi, kombucha, and sauerkraut will only get you so far if you are not consuming enough prebiotic fiber for the probiotics to eat. We call this seed (taking probiotics or probiotic foods) and feed (giving food to the good bacteria to flourish).

When probiotics feed on and break down (ferment) these prebiotic foods in the colon, a beneficial short chain fatty acid called butyric acid is formed. Often used interchangeably with the term butyric acid when discussing gut health, butyrate is the preferred energy source for the cells in the colon. While more studies are needed, butyrate has been studied for its roles in colon cancer prevention, insulin resistance/diabetes, obesity reduction, atherosclerosis, and chronic inflammation. Remember that what happens in the gut, doesn’t stay in the gut. We wrote about this more here.

Here are some foods that are some good food sources of prebiotic fiber:

o Asparagus
o Banana (especially green bananas = resistant starch)
o Barley
o Dandelion greens
o Eggplant
o Artichokes
o Leeks
o Legumes
o Oats
o Onions
o Peas
o Potatoes
o Whole grains

There are many other fiber-rich fruits and vegetables that are great to eat but the above stand out as good sources of prebiotics specifically.

If you are thinking, “hey I’d love to eat these foods, but these fiber-rich foods really cause me discomfort whenever I eat them”, there’s a good chance you have some level of Dysbiosis (microbial imbalance) going on in your gut. At Root, we do comprehensive stool testing to help you get to the root of your health concerns. This stool testing actually can tell us how well you are doing with butyrate production and if you are eating enough fiber. Remember that even if you aren’t having digestive issues, other symptoms such as joint pain, fatigue, and brain fog could be due to imbalances in your gut microbiota.

If you’d like to set up a free 15-minute call with Dr. Armstrong or Kelsey Stricklen, MS RD CLT to discuss if we are a good fit to get to the root of your health concerns, you can contact us here.



Wong, JM, de Souza R, Kendall CW, Emam A, & Jenkins DJ.  Colonic health: fermentation and short chain fatty acids.  J Clin Gastroenterolog. 2006;40(3):235-43.


Dahl WJ, Agro NC, Eliasson AM, Mialki KL, Olivera JD, Rusch CT, & Young CN.  Health Benefits of Fiber Fermentation.  J Am Coll Nutr. 2017; 36(2): 127-136. doi: 10.1080/07315724.2016.1188737


McNabney SM & Henagan TM.  Short Chain Fatty Acids in the Colon and Peripheral Tissues: A Focus on Butyrate, Colon Cancer, Obesity, and Insulin Resistance.  Nutrients. 2017;9(12). doi: 10.3390/nu9121348.

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