Fillers and stabilizers
Synthetic fiber additives
Definition
What it is
Synthetic fiber additive: soluble corn fiber, resistant dextrin, or polydextrose added to boost fiber label claims; not equivalent to whole food fiber and at high doses can cause GI distress.
On the label
Label names covered by this flag
- synthetic fiber additives
- soluble corn fiber
- corn fiber
- resistant dextrin
- polydextrose
- resistant maltodextrin
Regulation
Regulatory status
No bans or restrictions are recorded for this ingredient in the jurisdictions clearlabel tracks (US, EU, UK, Canada, Japan, Australia/NZ, Brazil).
Explainer
In plain language
Synthetic and isolated fiber additives are refined fibers like soluble corn fiber, resistant dextrin, and polydextrose that manufacturers add to boost the fiber number on a nutrition label. They are made by processing starches, often from corn, into forms the body does not fully digest. Their job is to raise fiber claims and sometimes add bulk or mild sweetness without much taste.
Assessment
Why it is flagged
These fibers are permitted by the FDA, and some, like polydextrose, are long established as food additives. The debate is about whether they deliver the same benefits as fiber from whole foods. The FDA reviewed isolated fibers in 2016 and 2018 and recognized only certain ones as counting toward the fiber declaration after evaluating evidence for a physiological benefit. At higher doses these fibers are associated with gas, bloating, and loose stools in some people, because they ferment in the gut. Clear Label flags them as low severity so users can see when a high fiber claim comes from added isolates rather than whole ingredients, and test any digestive patterns in their own logs.
In the aisle
Where it commonly shows up
- High-fiber protein and snack bars
- Reduced-sugar or keto candies
- Fiber-fortified cereals and granola
- Sugar-free ice cream and frozen desserts
- Meal-replacement shakes and powders
- Reduced-calorie baked goods
Practical
Reading the label
Look for soluble corn fiber, resistant dextrin, resistant maltodextrin, or polydextrose in the ingredient list, often on products advertising a big fiber number or low net carbs. A high fiber figure next to a short whole-food ingredient list usually points to added isolates.
Alternatives
If you want to avoid it
Some people choose foods that reach their fiber from whole ingredients like oats, beans, fruit, and vegetables. Comparing two similar bars, one with added fiber isolates and one without, is usually enough to see the difference on the label.
FAQ
Common questions
Is added fiber the same as fiber from vegetables?
Not exactly. Isolated fibers like resistant dextrin behave differently from the mixed fiber in whole foods, and the FDA only counts certain isolated fibers toward the label after reviewing evidence for a benefit.
Why do these fibers cause bloating for some people?
They pass to the lower gut where bacteria ferment them, which can produce gas and loose stools at higher doses. Individual tolerance varies, so it is a pattern worth tracking in your own logs.
Citations
Sources
Citation
Primary reference
About this page: the definition, label names, severity, and regulatory chips come from the clearlabel ingredient taxonomy, the same data the scanner uses to score products. Research summaries describe associations reported in published studies, not diagnoses; individual responses vary. Scan any product with clearlabel to see which of its ingredients carry flags.