How do Fiber One bars have so much fibre? The science of added ingredients

December 17, 2025 •

3 min read

Did you know some Fiber One bars can provide over 30% of your daily fiber needs in a single serving? This high fiber density isn't a result of whole grains alone but is largely achieved through the strategic use of specific, isolated fiber additives during production.

Quick Summary

Fiber One bars contain high amounts of fiber primarily from added ingredients like chicory root extract (inulin), soluble corn fiber, and allulose to boost content and improve texture, supplementing the whole grain components.

Key Points

Isolated Fibers: Fiber One bars boost their fiber content with concentrated additives like chicory root extract (inulin) and soluble corn fiber.
Prebiotic Effects: Chicory root extract and soluble corn fiber act as prebiotics, feeding beneficial gut bacteria.
Allulose as Fiber: Some bars contain allulose, a low-calorie sweetener that the FDA permits to be counted toward a product's total fiber.
Whole Grains Play a Role: Natural fiber from whole grains like oats and barley contributes to the total fiber, but not as significantly as the added ingredients.
Digestive Sensitivity: The rapid fermentation of isolated fibers can cause gas, bloating, and other digestive issues for some people.
Not a Whole-Food Substitute: While effective for raising fiber numbers, the added fibers do not provide the full spectrum of nutrients found in whole-food fiber sources.
Varying Ingredients: The exact fiber sources and amounts differ depending on the specific Fiber One product, so it's important to check the ingredient list.

The Science Behind the Fibre Count

While a bar's ingredient list might include whole grains like oats and barley, a significant portion of its fiber comes from concentrated, isolated sources. These engineered fiber additives allow manufacturers to create palatable, high-fiber products that are low in calories and sugar, which can be challenging with traditional whole-food fiber sources. By using these ingredients, Fiber One can deliver a substantial fiber boost in a compact, satisfying bar.

Chicory Root Extract (Inulin)

One of the most prominent ingredients listed in many Fiber One bars is chicory root extract, which is a source of inulin. Inulin is a soluble, prebiotic fiber extracted from the chicory plant.

Function: Inulin adds bulk to the bar and serves as a fat or sugar replacer while contributing significantly to the fiber count.
Prebiotic Benefits: As a prebiotic, it feeds the beneficial bacteria in the gut, promoting a healthy gut microbiome.
Potential Downsides: For some individuals, especially those with sensitive digestive systems, high doses of inulin can cause digestive discomfort, such as gas, bloating, and diarrhea.

Soluble Corn Fiber

Many Fiber One bars also contain soluble corn fiber, a highly processed, nondigestible carbohydrate derived from cornstarch.

Function: This ingredient acts as a prebiotic, sweetener, and bulking agent. It is often used to thicken processed foods and can help improve texture.
Benefits: It has a low glycemic index and does not cause a sharp spike in blood sugar, making it a common choice for low-carb and keto-friendly products.
Source Concerns: It's important to note that soluble corn fiber is often derived from genetically modified corn crops.

Allulose

Some specific Fiber One varieties, particularly lower-calorie options, list allulose in their ingredients. Allulose is a rare sugar that the body doesn't metabolize, meaning it contributes minimal calories.

FDA Labeling: In the U.S., the FDA allows allulose to be listed as fiber on the nutrition facts label.
Net Carbs: This is a key reason why some bars can boast a low net carb count; allulose, along with other fiber sources, is subtracted from the total carbs.
Prebiotic Effects: Similar to inulin, allulose also exhibits prebiotic fiber properties.

Whole Grains vs. Added Fibers: A Comparison

While Fiber One bars do contain some whole grains, a notable difference exists between the fiber from these natural sources and the concentrated, added fibers used for processing.


Feature	Whole Grain Fiber (e.g., Oats)	Added/Isolated Fiber (e.g., Inulin, SCF)
Source	Naturally occurring in whole, unprocessed grains.	Extracted and concentrated from plants or created synthetically.
Micronutrients	Includes associated vitamins, minerals, and antioxidants.	Isolated from its natural source, lacks the nutrient density of whole foods.
Digestive Effects	A balanced mix of soluble and insoluble fiber; generally well-tolerated when increased gradually.	Can ferment quickly in the gut, potentially causing bloating, gas, and discomfort.
Processing	Minimally processed to retain natural structure.	Highly processed using enzymatic hydrolysis and other methods.
Function	Provides bulk and promotes healthy digestion naturally.	Used to increase fiber content, improve texture, and replace sugar/fat.

Nutritional Context and Considerations

While Fiber One bars can be an effective way to boost fiber intake, particularly for those who struggle to meet their daily requirements, they are not a substitute for fiber from whole foods. Whole foods like fruits, vegetables, and legumes offer a wider range of nutrients that processed bars often lack. Furthermore, the rapid fermentation of added fibers can be problematic for some, especially those with sensitive digestive systems like IBS. Moderation is key, and it is recommended to increase fiber intake gradually to minimize potential gastrointestinal side effects.

Conclusion

In summary, the high fiber content of Fiber One bars is a result of using concentrated, isolated fiber sources such as chicory root extract (inulin), soluble corn fiber, and allulose. These additives allow the brand to meet a significant portion of daily fiber recommendations while keeping calorie and sugar counts low. While they can be a convenient supplement, they don't offer the same complete nutritional profile as whole-food fiber sources. Understanding the role of these specific ingredients provides a clearer picture of how these popular snack bars are formulated. For those interested in maximizing their intake of whole-food fibers, resources on healthy eating can offer valuable guidance.

Frequently Asked Questions

Chicory root extract is a source of inulin, a soluble and prebiotic fiber that adds bulk and boosts the bar's fiber content. Manufacturers also use it as a low-calorie replacement for sugar and fat.

Yes, for some people, the high concentration of certain added fibers like inulin can cause digestive discomfort, including gas and bloating. This happens because these fibers ferment quickly in the gut.

Allulose is a rare, low-calorie sugar that the body doesn't absorb. The FDA allows it to be counted as a fiber on U.S. nutrition labels, though it functions differently than traditional fiber sources.

Soluble corn fiber is a processed dietary fiber derived from cornstarch. It serves as a prebiotic, texturizer, and sweetener and is used to increase the fiber content in many processed foods, including Fiber One bars.

While they provide a convenient fiber boost, they are not a substitute for whole-food fiber. Whole grains, fruits, and vegetables offer a broader range of nutrients, minerals, and antioxidants that isolated fiber additives do not.

To minimize potential digestive discomfort, it is best to gradually increase your fiber intake. Additionally, ensure you drink plenty of water to help the fiber move smoothly through your digestive system.

Low-carb Fiber One bars achieve their fiber count by including specific ingredients like allulose, which contribute to the 'fiber' category on the nutrition label but not to net carbs, as the body does not metabolize it.

No, the ingredients vary by product line and flavor. For example, some may contain more chicory root extract, while others might feature more soluble corn fiber or allulose, so it is important to check the specific bar's label.