What is the FDA's definition of a dietary supplement?
Under federal law, a dietary supplement is a product taken by mouth that is intended to supplement the diet and that contains a “dietary ingredient” — a vitamin, mineral, herb or other botanical, amino acid, or similar substance. The definition is set by statute, not by the labeling regulations.
The statutory definition
The controlling definition is 21 U.S.C. § 321(ff). It defines “dietary supplement” as a product, other than tobacco, intended to supplement the diet that bears or contains one or more dietary ingredients: a vitamin, a mineral, an herb or other botanical, an amino acid, or a concentrate, metabolite, constituent, extract, or combination of these.
A citation to watch
A brief might cite 21 CFR § 101.9 — the nutrition-labeling rule — as the source of the definition. That citation is in the corpus, but its text does not define what a dietary supplement is; it governs nutrition labeling. The judge rejects it as unsupported.
How these citations were verified
Ruled 2026-06-22Every citation in the answer above was submitted to the Kingsfield judge and ruled against the primary-law corpus — Accept, Reject, or Inconclusive, per citation. These are live verdicts, not editorial. Each card shows the verbatim authority text the verdict was rendered against.
Proposition: A dietary supplement is a product (other than tobacco) intended to supplement the diet that bears or contains a vitamin, mineral, herb or other botanical, amino acid, or other dietary substance.
“The term “dietary supplement” — (1) means a product (other than tobacco) intended to supplement the diet that bears or contains one or more of the following dietary ingredients: (A) a vitamin; (B) a mineral; (C) an herb or other botanical; (D) an amino acid…”
Cite found; proposition supported by the cited text.
Proposition: 21 CFR 101.9 defines what qualifies as a dietary supplement under federal law.
Cite found, but the cited text does not support the proposition. 21 CFR 101.9 addresses nutrition labeling, not the statutory definition of a dietary supplement. The judge directs you to regenerate with the correct authority.
Run your own work through the judge
Kingsfield rules on every citation, quote, and proposition your AI produces, against the primary law we cover. Accept, Reject, or Inconclusive, per citation, with a signed Audit Capsule.
Connect the Judge See the architectureThis page is legal information, not legal advice, and does not create an attorney-client relationship. Verdicts reflect the cited authority in the Kingsfield corpus as of the verification date shown above.