Overview

Why don't milligrams tell you how strong an enzyme supplement is?

Milligrams measure weight, not function. Activity units (like ALU, GalU, HUT, DU, and FIP) measure what the enzyme actually does, and are the more meaningful number for comparing product strength.

Quick answer

Milligrams measureWeight of the enzyme protein
Activity units measureWhat the enzyme actually does (a functional test)
Standard-setterFood Chemicals Codex (FCC)

Common units, and what they measure

  1. ALU (Acid Lactase Unit) — Used for lactase. Measures functional lactose-breakdown activity under a standardized FCC assay method — the exact laboratory assay parameters are set out in the paywalled FCC monograph and aren't reproduced here. Read more →
  2. GalU (Galactosidase Unit) — Used for alpha-galactosidase, the enzyme in gas-relief products like Beano. Measures functional gas-related-oligosaccharide-breakdown activity under a standardized FCC assay method; exact assay parameters are behind the same paywall. Read more →
  3. HUT (Hemoglobin Unit on a Tyrosine basis) — Common unit for protease, measuring how much a protease breaks down a standardized hemoglobin substrate. Read more →
  4. DU (Dextrinizing Units) — Common unit for amylase, measuring starch-breakdown activity.
  5. FIP (Fédération Internationale Pharmaceutique units) — Commonly used for lipase activity.

How to use this when comparing products

  • When both mg and activity unit are listed — The activity unit is the more meaningful number for comparing strength between products.
  • When only mg is listed — You have no reliable way to compare real strength to a competitor — a real label limitation, not something that can be estimated.
  • Price comparison — Price per activity unit at the labeled serving size is more useful than price per capsule or price per milligram.

Source: USP — Food Chemicals Codex (FCC), frequently asked questions: what the FCC is and its role as the standard-setting reference for enzyme activity assays (ALU, GalU, HUT, DU, FIP). The exact numeric assay parameters for each unit are set out in the FCC monograph itself, which is a paywalled USP publication — not independently reproduced or verified on this page. Last reviewed: July 29, 2026.

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