21 CFR 101.91 established FDA's federal definition of "gluten-free" for food labeling, effective August 5, 2014 for conventional foods and August 12, 2020 for fermented or hydrolyzed foods. The rule was enacted under the FDA Food Safety Modernization Act and applies to any food bearing a voluntary "gluten-free," "free of gluten," "without gluten," or "no gluten" claim.
The Federal Definition of "Gluten-Free"
Under 21 CFR 101.91(a)(3), a food may bear a "gluten-free" claim only if it meets all of the following conditions:
The food must not contain:
Any ingredient that is a gluten-containing grain (wheat, rye, barley, or their crossbred hybrids such as triticale)
Any ingredient derived from a gluten-containing grain that has not been processed to remove gluten (e.g., wheat flour)
Any ingredient derived from a gluten-containing grain that has been processed to remove gluten (e.g., wheat starch), if the use of that ingredient results in 20 ppm or more of gluten in the finished food
And:
Any unavoidable gluten from cross-contact must also be below 20 ppm in the finished food
The 20 ppm threshold is based on scientific evidence that levels below 20 ppm are generally safe for most people with celiac disease, and it aligns with the limit of reliable detection using validated analytical methods.
Gluten-Containing Grains
Under 21 CFR 101.91(a)(1), the following are gluten-containing grains:
Wheat — any species belonging to the genus Triticum, including durum wheat, spelt, kamut, einkorn, and emmer
Rye — any species belonging to the genus Secale
Barley — any species belonging to the genus Hordeum
Crossbred hybrids — e.g., triticale (a wheat-rye hybrid)
Oats are not in the FDA definition of gluten-containing grains. However, oats are frequently cross-contaminated with wheat during growing, harvesting, and processing. Brands using oats in gluten-free products must use purity protocol oats that are tested to confirm < 20 ppm gluten in the finished product.
Wheat Starch and Processed Grain Derivatives
The rule allows ingredients derived from gluten-containing grains that have been processed to remove gluten — such as wheat starch — to appear in a "gluten-free" labeled product, provided that the use of the ingredient does not result in ≥ 20 ppm gluten in the finished food.
This is significant for brands using:
Wheat starch in certain gluten-free formulations
Wheat-derived dextrose, glucose syrup, or maltodextrin — these are generally considered gluten-free because the protein (gluten) is removed during processing, but brands should obtain supplier documentation confirming gluten levels
Fermented and Hydrolyzed Foods (Extended Compliance)
FDA extended the compliance date to August 12, 2020 for fermented or hydrolyzed foods (e.g., vinegar, soy sauce, miso, beer, certain cheeses) because conventional gluten testing methods cannot reliably detect gluten in these products after fermentation breaks down the proteins.
For these products, brands must:
Ensure no gluten-containing grains are used as ingredients
Implement process controls to prevent cross-contact
Use testing methods validated for the specific fermented or hydrolyzed matrix
Voluntary vs. Mandatory Claim
The "gluten-free" claim is voluntary — FDA does not require foods to be labeled as gluten-free. However:
If a food bears a gluten-free claim, it must comply with 21 CFR 101.91 in all respects
FDA's position is that the claim implies a safety representation to celiac consumers — making a false or unsubstantiated claim creates both regulatory and liability exposure
Dietary Supplements and Gluten-Free Claims
The 21 CFR 101.91 rule applies to dietary supplements as well as conventional foods. A supplement bearing a "gluten-free" claim must meet the same < 20 ppm standard.
Common supplement ingredients with gluten exposure risk:
Oat-based ingredients (oat bran, oat fiber, oat beta-glucan) — cross-contact risk
Barley grass or wheat grass powder — derived from gluten-containing plants; processing does not remove gluten from grass powders
Malt extract — derived from barley; contains gluten
Certain starch excipients (some modified starches are wheat-derived)
Capsule ingredients — most gelatin and vegetarian capsule shells are inherently gluten-free, but contamination during filling can occur
"No Gluten Ingredients" vs. "Gluten-Free"
There is an important practical distinction between:
"No gluten ingredients" — a truthful claim that the formulation contains no gluten-containing grains or their derivatives, but does not address cross-contact
"Gluten-free" — requires that the finished product contain < 20 ppm gluten, accounting for cross-contact during manufacturing
A product made without gluten ingredients but manufactured in a facility that also processes wheat may still test above 20 ppm due to cross-contact. Using "gluten-free" on such a product is a violation of 21 CFR 101.91.
Third-Party Certification
FDA does not require third-party gluten-free certification. However, brands using programs such as the Gluten-Free Certification Organization (GFCO) (≤ 10 ppm threshold), NSF Gluten-Free (≤ 20 ppm threshold), or Certified Gluten-Free from other recognized bodies provide consumers and retailers with additional assurance.
Third-party certification does not eliminate FDA's independent enforcement authority — brands are responsible for compliance with 21 CFR 101.91 regardless of certification status.
How Truli Helps with Gluten-Free Claim Compliance
Ingredient screening: Truli identifies wheat, barley, rye, and crossbred hybrid-derived ingredients in formulations bearing gluten-free claims, including less obvious sources like malt extract, barley grass, and wheat-derived excipients
Cross-contact risk flagging: Truli surfaces manufacturing facility questions for brands making gluten-free claims without dedicated gluten-free facilities
Supplement compliance audit: Truli checks that supplements bearing gluten-free claims have identified and resolved all potential gluten sources including excipients and encapsulation materials
Related Regulations
21 CFR Part 101 — FDA food labeling requirements
FALCPA and FASTER Act — Wheat is a major allergen under FALCPA; gluten-free and allergen labeling interact
21 CFR 101.4 — Ingredient List Requirements — Ingredient declaration rules
Frequently Asked Questions
Is oat flour gluten-free?
Not automatically. Oats are not a gluten-containing grain under 21 CFR 101.91(a)(1), but conventional oats are frequently cross-contaminated with wheat. To use oats in a gluten-free product, brands must use purity protocol oats and test the finished product to confirm < 20 ppm gluten.
Does "wheat-free" mean the same as "gluten-free"?
No. "Wheat-free" indicates the absence of wheat specifically but does not address rye, barley, or cross-contamination. A product could be wheat-free but still contain barley malt and would not qualify as "gluten-free" under FDA's definition.
Can I make a gluten-free claim on a product made in a shared facility?
Yes, if you can demonstrate through testing and process controls that the finished product contains < 20 ppm gluten. Many brands use shared facilities successfully with proper cleaning validation, dedicated lines or scheduling, and finished product testing. The claim is based on the product, not the facility designation.
A note from Truli: Truli is not a law firm, and this article does not constitute or contain legal advice or create an attorney-client relationship. When determining your obligations and compliance with respect to relevant laws and regulations, you should consult a licensed attorney.
Last updated: April 2026. Reflects 21 CFR 101.91 as of April 2026. Truli monitors FDA enforcement actions on gluten-free claims. Book a demo to see how.
