Lactase is a dietary supplement that consists of an enzyme that helps to break down lactose for patients who are lactose intolerant.

Lactose is a disaccharide consisting of galactose and glucose. It is commonly present in milk.


Units of lactase activity are usually given in FCC units. The FCC is the Food Chemicals Codex. This is an international compendium of standards for food ingredients. The U.S. Pharmacopeial Convention (USP) assumed responsibility from the Institute of Medicine (IOM) in 2006.


1 FCC unit is the amount of enzyme that will hydrolyze 1 micromole per minute of o-nitrophenol at 37°C and a pH of 4.5 over 15 minutes using as substrate o-nitrophenol-beta-D-galactopyranoside.


1 FCC unit equals 1 ACU (acid lactase unit).


The greater the lactose load the larger the amount of lactase required to hydrolyze it.


The USP standard shows 85,300 USP lactase units per gram, or 85.3 USP units per mg.

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