What are the sources of dietary fiber according to the FDA?

October 22, 2025 •

2 min read

In 2016, the FDA established a new definition for dietary fiber for use on Nutrition Facts labels. This update clarifies what types of fiber can be counted, impacting both consumers and manufacturers.

Quick Summary

The FDA outlines two categories for dietary fiber: natural 'intrinsic and intact' fibers in plants and 'isolated or synthetic' fibers with demonstrated health benefits. This classification governs food labeling accuracy.

Key Points

FDA Fiber Categories: The FDA classifies dietary fiber as 'intrinsic and intact' (natural plant fiber) or 'isolated or synthetic' (added fiber with a proven health benefit).
Natural Fiber Sources: Fiber naturally found in whole grains, legumes, vegetables, and fruits is automatically counted.
Approved Added Fibers: Isolated fibers like psyllium, beta-glucan, pectin, and guar gum require FDA approval based on demonstrated health effects.
Solubility Classification: Fiber is also described as soluble (dissolves in water, helps cholesterol) or insoluble (adds bulk, aids regularity).
Recommended Intake: The Daily Value for fiber is 28 grams, achievable through diverse whole foods.

Intrinsic and Intact Fibers

The FDA includes fibers that are 'intrinsic and intact' within plants in its definition of dietary fiber. These are naturally found in whole foods such as fruits, vegetables, whole grains, and legumes, nuts, and seeds. Because these fibers are naturally present, no additional evidence is needed for related health claims. Bran from cereal grains is also in this category.

Isolated or Synthetic Fibers

This category includes 'isolated or synthetic non-digestible carbohydrates' added to foods. For these to be listed as dietary fiber, scientific evidence must show a beneficial health effect. The FDA has approved several types of these added fibers.

FDA-approved isolated or synthetic fiber examples:

Beta-glucan soluble fiber
Psyllium husk
Pectin
Guar gum
Locust bean gum
Cellulose
Hydroxypropylmethylcellulose The FDA is considering adding more fibers, such as inulin and resistant maltodextrin, to this list.

Soluble vs. Insoluble Fiber: A Comparison

Dietary fiber is also often categorized based on whether it dissolves in water. Both soluble and insoluble fibers are beneficial and found in various natural sources.


Feature	Soluble Fiber	Insoluble Fiber
Dissolves in Water	Yes, forms a gel.	No.
Primary Function	Slows digestion, helps blood sugar and cholesterol.	Adds bulk, aids regularity.
Fermentation	Generally fermentable.	Less fermentable.
Common Sources	Oats, beans, apples, psyllium.	Whole wheat, nuts, vegetables.
FDA Context	Includes many approved added fibers.	Includes intrinsic fibers from whole grains and vegetables.

How to Ensure Adequate Fiber Intake

The FDA recommends incorporating various fiber types into your diet. The Daily Value is 28 grams based on a 2,000-calorie diet.

Focus on whole foods like fruits, vegetables, whole grains, nuts, and legumes for natural fibers.
Use Nutrition Facts labels to check the fiber content of foods.
Increase fiber intake gradually and drink enough water.
Foods with added fibers can supplement intake but should not replace whole foods.

Conclusion

The FDA's dietary fiber definition provides clarity for food labeling, distinguishing natural plant fibers from added ones that need demonstrated health benefits. Understanding these classifications and consuming a variety of fiber-rich whole foods helps meet recommendations and supports health benefits. Further information on fiber benefits is available from resources like the Harvard T.H. Chan School of Public Health.

Frequently Asked Questions

The FDA defines dietary fiber as non-digestible carbohydrates and lignin found either naturally in plants ('intrinsic and intact') or added as isolated or synthetic non-digestible carbohydrates with proven health benefits.

Natural fiber in whole foods counts automatically. Added isolated or synthetic fibers must demonstrate a health benefit to be included on the label.

Fibers in whole grains, fruits, vegetables, beans, peas, and lentils are examples of intrinsic and intact fibers.

Approved isolated fibers include beta-glucan, psyllium husk, cellulose, guar gum, pectin, and locust bean gum, among others.

The FDA definition includes both types. Soluble fiber helps with cholesterol and blood sugar, while insoluble fiber supports digestive health.

Yes, the Daily Value used for labeling is 28 grams for a 2,000-calorie diet.

The 2016 update aimed to ensure only fibers with demonstrated health benefits were counted on labels, providing clearer information to consumers.