Dietary Fiber – Navigating the FDA’s Definition
Author: Mollie Van Alst, Analytical Services Manager of Eurofins Scientific Inc. (Eurofins Nutritional Analysis Center) in Des Moines, IA
What really is dietary fiber according to the most recent FDA regulations? This is a question many food manufacturers are asking today, especially with the most recent and innovative market trends to include upcycled & novel ingredients, while still meeting the “better for you” shift in consumer expectations. If you’re one of those businesses, you’ve found the right place. This blog by our scientists will help break down the FDA’s most recent definition of fiber as well as provide examples of ingredients used in the industry today.
The Official Definition
The most recent definition of dietary fiber as it relates to nutrition labeling contains two major parts:
- Non-digestible soluble and insoluble carbohydrates (with 3 or more monomeric units), and lignin that are intrinsic and intact in plants.
- Isolated or synthetic non-digestible carbohydrates (with 3 or more monomeric units) determined by FDA to have beneficial physiological effects.
Part 1 – Intrinsic or Intact
The first part of the definition is the most obvious and straightforward.
Naturally occurring fiber (sometimes called "intrinsic") can be found in foods such as vegetables, whole grains, fruits, cereal bran, flaked cereal, and flours. They are also called "intact" since they have not been removed from the food source.
These types of fibers are considered to meet the definition, because the fiber is found naturally in the ingredient and are not manipulated in any way.
Part 2 – Isolated or Synthetic
The second part is where many within the industry struggle to understand. A great example is pea fiber – an ingredient we see being used more frequently today. One might think “peas are natural, so the fiber must also be natural.”
Unfortunately, that is not necessarily true – and it all has to do with the processing of the ingredient. For example, inner pea fiber, also known as cotyledon pea fiber, is actually classified as an isolated fiber.
Isolated fibers are created from a processing step like crystallization, concentration, solvent extraction, and others done on the plant source. They are not natural in form, but are removed or isolated from the raw material just like our example of pea fiber above.
Approved Dietary Fibers
In May of 2016, the FDA final rule included an initial list of seven isolated or synthetic carbohydrates that meet the definition. Those fibers are:
- Beta-Glucan
- Cellulose
- Guar Gum
- Hydroxypropylmethylcellulose
- Locust Bean Gum
- Pectin
- Psyllium Husk
After receiving several petitions from the industry and subsequently reviewing those petitions, the FDA published a list of additional fibers that are expected to meet the FDA’s definition. The final rule has not yet been amended to include these, but the FDA is allowing their inclusion as dietary fiber under enforcement discretion. We will talk about what this means a bit later.
The fibers added in 2018 are:
- Arabinoxylan
- Alginate
- Galactooligosaccharides (GOS)
- High Amylose Starch (RS2)
- Inulin & Inulin-type Fructans
- Mixed Plant Cell Wall Fibers
- Polydextrose
- Resistant Maltodextrin/Dextrin
Then in 2019 and 2020, two more additions were added, bring us to the final list of ingredients to date:
- Cross-linked Phosphorylated RS4 – 2019
- Glucomannan – 2020
Of the entire list, one has caused a great amount of confusion for many – Mixed Plant Cell Wall Fibers.
Mixed Plant Cell Wall Fibers
According to the FDA, mixed plant cell wall fibers are ingredients that contain two or more of the following plant cell wall fibers in varying proportions:
- Cellulose
- Pectin
- Lignin
- Beta-Glucan
- Arabinoxylan
The FDA offers a non-exhaustive list of examples it expects to include as dietary fiber, including:
Apple fibers, bamboo fibers, barley fibers, carrot fibers, citrus fibers, cocoa fibers, corn fibers (e.g., corn hull fiber), cotton seed fibers, oat fibers (e.g., oat hull fiber), pea fibers (e.g., pea hull fiber, pea seed coat fiber, inner cotyledon pea fiber), rice brand fibers, soy fibers (e.g., soy hull fiber, soy polysaccharide, soy cotyledon fiber), sugar beet fibers, sugar cane fibers, and wheat fibers.
As mentioned briefly above with the example of pea fiber, some non-digestible carbohydrates can have the same name, but are processed differently. Consequently, just the name of an ingredient (such as pea fiber) may not be symbolic of whether it is “intrinsic & intact” or “isolated”. Just if you thought it couldn’t get any more complex, some types of processing methods can produce varying degrees of isolation as well. Thus, with all of these factors at play, the FDA will exercise enforcement discretion.
So what is enforcement discretion? Essentially, it means that even if the ingredient in question meets the definition of a beneficial dietary fiber, the FDA can choose to not enforce its use – likely due to a lack of data to support the ingredient’s benefits or lack of appropriate ingredient documentation & quantity used. This leads us to our final topic of documentation.
Documentation
The most important piece and the key to meeting the FDA’s regulations falls back on documentation – especially for multi-ingredient finished goods that may contain a mixture of both qualifying and non-qualifying ingredients (dietary fiber). These foods make up a large chunk of the market and most everyone has something in their kitchen that falls into this category.
With the complexities stated above, you can guess that testing for fiber can be challenging. Testing can breakdown the amount of fiber categorically into soluble & insoluble by molecular weight, but it cannot assign those values to each specific ingredient in the product. Due to these confines of current analytical methods, manufacturers should keep written records to confirm the amount of added non-digestible carbohydrates that do not meet the definition of dietary fiber for products that contain a mixture.
For more information about dietary fiber or our testing capabilities, please feel free to reach out to our scientists to discuss more!
