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Study Shows This Little-Known Fiber Increases Good Bacteria In The Gut*

Molly Knudsen, M.S., RDN
Author:
June 13, 2025
Molly Knudsen, M.S., RDN
Registered Dietitian Nutritionist
By Molly Knudsen, M.S., RDN
Registered Dietitian Nutritionist
Molly Knudsen, M.S., RDN is a Registered Dietician Nutritionist with a bachelor’s degree in nutrition from Texas Christian University and a master’s in nutrition interventions, communication, and behavior change from Tufts University. She lives in Newport Beach, California, and enjoys connecting people to the food they eat and how it influences health and wellbeing.
Image by Svitlana Hulko / iStock
June 13, 2025

Having a healthy gut microbiome—with a wide range of beneficial bacteria and other microbiomes—improves everything from digestion to immune function, mood, mental health, and metabolism. 

One of the best ways to support your gut microbiome is by eating prebiotic fibers. Prebiotic fibers are a specific type of fiber found in plants that only the good bacteria in the gut can ferment. The thing is, most of us fall woefully short on our daily fiber intake. That's where specific fiber supplements come into play. 

And researchers of a new study found that even adding a few grams of this prebiotic fiber1 to your diet a day (a fiber that we often don't find on our plates) can positively shift the composition of our gut microbiome. Here's what you need to know. 

About the study

For this study, researchers wanted to see how partially hydrolyzed guar fiber influences the gut microbiome. 

What is partially hydrolyzed guar fiber, you ask? Well, it's a fiber derived from the seeds of the guar plant. When guar fiber is partially hydrolyzed (aka broken down), it makes the fiber more gentle and easy to digest—unlike other fibers that tend to gel in water or sit like a rock in your stomach. 

To evaluate this, 33 healthy adults consumed 3 grams, 6 grams, and a placebo a day for 14 days (with a two-week break between each phase). Stool samples were collected before and after each treatment to study gut bacteria. They also measured stress via cortisol levels found in saliva. 

And to more easily link any changes in the gut to the guar fiber (and not just other fibers in the diet), each person followed a low-fiber diet of 14 grams of fiber or less per day. 

While this is a low-fiber diet, it's actually representative of the standard American diet. On average, adults in the U.S. consume around 16 grams of fiber a day2 versus the recommended 25 to 38 grams.  

Guar fiber improved measures of gut health 

Overall, daily consumption of guar fiber improved several measures of gut health:*

  • Guar fiber increased good gut bacteria like Akkermansia and Verrucomicrobia: Both of these bacteria are linked to better gut barrier function and metabolic health.
  • Guar fiber decreased the potentially harmful bacteria Dorea and Sutterella: These microbes are associated with digestive distress.
  • Improved stool consistency and lowered cortisol: This benefit was seen when folks consumed 6 grams of guar fiber a day, suggesting a potential impact on both digestive function and stress response.*

Why guar fiber stands out among other prebiotic fibers

There are so many supplements out there that use different fiber sources, but guar seems to stand out above the rest. 

Unlike some fibers that seem to trigger bloating, this partially hydrolyzed guar fiber is better tolerated. Plus, this study shows that even consuming as few as 3 grams of fiber a day can have measurable benefits for your gut.*

How to get more of this fiber 

If you're looking to bump up your fiber intake—particularly your prebiotic fibers—then adding a supplement to your routine is the most targeted route you can take. Of course, you can (and should) add some of these prebiotic-rich foods to your diet too!

mindbodygreen's organic fiber+ with prebiotic support is a great choice. This innovative formula was thoughtfully designed to provide 6 grams of fiber—the majority of which comes from the exact same brand of partially hydrolyzed guar fiber used in this study), as well as fiber from green kiwifruit and mushrooms. 

In addition to supporting the gut microbiome, guar fiber has been shown to:

The powder also disperses readily into hot or cold liquids and does not gel. It also goes great in oatmeal or yogurt bowls.

The takeaway

Consistent prebiotic fiber intake can have profound effects on your gut health and, therefore, your overall health. While this may be the first time you're hearing about guar fiber, it's something that should absolutely be on your radar. 

Adding a scoop of organic fiber+ with prebiotic support to your water, coffee, or breakfast is one of the easiest things you can do to significantly increase your fiber intake.*

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