Unlike most structure/function claims, "gluten-free" is not a matter of interpretation. The FDA established a specific regulatory definition under 21 CFR 101.91, and any food or supplement bearing the claim must meet that definition. Failing to do so isn't just a labeling error — it's a federal misbranding violation.
The FDA's Legal Definition of "Gluten-Free"
Under 21 CFR 101.91(a)(3), a product labeled "gluten-free" must:
Not contain any ingredient that is a gluten-containing grain (wheat, rye, barley, or their crossbred hybrids such as triticale)
Not contain any ingredient derived from a gluten-containing grain that has not been processed to remove gluten (e.g., wheat flour)
Not contain any ingredient derived from a gluten-containing grain that has been processed to remove gluten, if that processing results in 20 ppm or more gluten remaining in the food
Have any unavoidable presence of gluten in the finished product below 20 ppm
The 20 parts per million threshold is the critical number. It was established based on clinical research indicating that most people with celiac disease can tolerate gluten below 20 ppm without adverse effects. It is also the lowest level that scientifically valid analytical methods can reliably and consistently detect across a variety of food matrices.
What "Gluten-Free" Covers
The regulation applies to the term "gluten-free" and to equivalent claims: "no gluten," "free of gluten," and "without gluten." Under 21 CFR 101.91(b)(2), all of these variants are treated identically — they're all misbranded if the product doesn't meet the 20 ppm standard.
The rule covers dietary supplements as well as conventional foods. A supplement labeled "gluten-free" is subject to the same standard as a food product bearing the same claim.
Cross-Contamination and Manufacturing Controls
A product that uses inherently gluten-free ingredients can still fail to meet the gluten-free standard if cross-contamination during manufacturing introduces gluten above 20 ppm. For supplement brands using contract manufacturers, this means:
Verifying your manufacturer's facility controls for gluten cross-contact
Understanding whether gluten-containing ingredients are processed in the same facility or on the same equipment
Having testing protocols in place to verify finished product gluten levels
The regulation makes the brand (manufacturer, packer, or distributor) responsible for compliance — not the contract manufacturer. If your product is labeled gluten-free and tests above 20 ppm, your brand is liable regardless of who made it.
Fermented and Hydrolyzed Ingredients
Under 21 CFR 101.91(c)(2), when a product contains fermented or hydrolyzed ingredients, standard gluten analytical methods may not be available. In these cases, the manufacturer must make and keep records demonstrating that:
The product was gluten-free before fermentation or hydrolysis
Processing for potential gluten cross-contact has been evaluated
Where cross-contact risk exists, measures have been implemented to prevent gluten introduction
These records must be retained for at least two years after the product is introduced into interstate commerce.
The Wheat in Ingredient Statement Issue
Under 21 CFR 101.91(b)(3), a product that declares wheat in its ingredient list or in a "Contains wheat" allergen statement cannot also claim to be gluten-free — unless the ingredient statement immediately references that the wheat has been processed to meet FDA's gluten-free requirements.
Some supplement ingredients are derived from wheat but processed to remove gluten (wheat-derived starch, for example). These ingredients can appear in a gluten-free product only if the residual gluten is below 20 ppm — and if wheat is declared in the ingredient list, the label must explain the wheat has been processed to meet the gluten-free standard.
State Law Preemption
Under 21 CFR 101.91(d), the FDA's gluten-free standard expressly preempts any state or local law that establishes a different standard for the definition or use of "gluten-free." No state can impose a stricter or different gluten threshold for products sold in interstate commerce. This is one of the few areas where federal supplement labeling law explicitly overrides state-level variation.
Third-Party Certifications
Third-party gluten-free certifications (GFFS, NSF, etc.) are not required by law but provide a documented quality control framework and consumer credibility signal. Importantly, a third-party certification doesn't substitute for FDA compliance — a certified product can still be misbranded if it doesn't meet 21 CFR 101.91's standards. Certification programs typically use the same 20 ppm threshold, which aligns with FDA requirements.
A precise claim requires a precise compliance process
"Gluten-free" is one of the few supplement claims with a bright regulatory line. Meeting the standard requires testing, manufacturing controls, and documentation — not just an absence of gluten ingredients on your formula sheet. Truli's product compliance scans flag gluten-free claim issues and cross-reference your ingredient and manufacturing data against the 21 CFR 101.91 standard.
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.
