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Fiber 101: What Is Fiber, Benefits and Source

Fiber 101: What Is Fiber, Benefits and Source

This week we’re excited to introduce Amsey Bai, our Director of Ops who has a degree in Dietetics and is our in-house nutritionist. Amsey is our Jetson-encyclopedia. We go to her with questions about almost everything, including why we need Fiber.

We’ve all been told at some point to add more fiber to our diets, but what does that mean? Do we need to eat kale and broccoli every day? How does this improve our gut? Let’s dive into what fiber really is, why we need it and where to get the good stuff. 

Q: First of all what is fiber and what does it do?

A: Fiber is a type of carbohydrate because the components are sugar molecules. Since our body doesn’t produce enzymes that breakdown fiber, the fibers we eat can either exit our body as-is or feed through the gut microbiome. In general, fiber contributes the most to our intestinal health besides probiotics.

Q: What is the difference between soluble and insoluble fiber?  

A: Insoluble fibers enter and exit the human body as the same product except being chopped into pieces. They are the “bulk” component that helps stool formation. Soluble fibers feed and support gut bacteria growth. Gut bacteria digest the fibers and break them down into short-chain fatty acids (SCFA) and gas. Therefore, soluble fiber is the key component that impacts the population of the microbiome.

Q: What are the best sources of fiber?

A: There’s no “best” fiber of all because it depends on individual needs. For example, fibers with high viscosity block and slow down digestion, which assists in weight-loss and blood sugar control. However, if a person already has a nutrient absorption issue, this high viscosity may worsen one’s malnourished condition. Similarly, while fermentable fibers help increase microbiome diversity and health, some types also produce gas at the same time that contributes to bloating, which aggregates IBS symptoms. Consuming a variety of fruits and vegetables can provide you with various kinds of fiber. Some high fiber foods include; oatmeal, avocado, flaxseed, chia seed, artichokes, and pears. The table below gives you some more insight into the commonly known high-fiber food items.


Fibers Category Fermentable in gut Viscous Food Sources
(Oligofructose is a subgroup of Inulin)
Soluble Yes No/Low Chicory root, Jerusalem artichoke
Pectin Soluble Yes Yes Apples, strawberries, citrus
Beta-glucan Soluble Yes Yes Oats, Barley, shiitake mushroom, reishi mushroom
Mucilage Soluble Yes Yes Chia seed, Flaxseed
Gum, Glucomannan Soluble Yes Yes Konjac plant / Elephant yam - usually found as Yam noodles in the gluten-free section in grocery stores.
Gum, Guar Soluble Yes Yes Grounded endosperm of the guar plant, which usually used as food additives.
Mucilage, Psyllium Soluble No Yes Psyllium husk
Cellulose Insoluble Low No Vegetables in general (such as broccoli, kale, cabbage, etc.)
Lignin Insoluble Low No Whole Grain, legumes, vegetables, fruits, seeds


Q: How does fiber impact the microbiome?

A: There are two groups of fiber, soluble and insoluble. Insoluble fiber doesn’t impact the microbiome but soluble fiber plays a key role in the microbiome population. Soluble fiber is the fuel of bacteria and supports microbiome reproduction. Gut bacteria produce the enzyme to breakdown the sugar molecule bonds in the intestine, which feeds certain bacteria and continuous fermentation. If a person has trouble adding these types of foods to their daily diet – a prebiotic fiber supplement (like Gut Prep) may help feed the good bacteria in the gut. 

Q: Can you get too much fiber? What happens?

A: The 2015-2020 American Dietary Guideline suggests fiber intake ranges from 25-30g/day for adults. However, there’s no upper limit set yet for fiber. More research is needed to provide detailed guidance about fiber upper limits. The reaction to fiber varies by individual and the type of fiber taken.