Lactase

Also known as lactaid, lactase enzyme.

Last reviewed October 9, 2026 · Jump to references

What is Lactase?

In plain words

Lactase is an enzyme, a protein that breaks down the sugar in milk, called lactose. It works in the gut to split lactose into two smaller sugars that the body can absorb. Researchers study supplemental lactase for reducing gas, bloating, and diarrhea in people who have trouble digesting lactose. Evidence supports this use, but how well it works varies.

Technical definition

Lactase is a β-galactosidase enzyme; human intestinal lactase is part of the brush-border protein lactase-phlorizin hydrolase, while supplemental lactase is typically derived from fungi or yeasts. It acts on lactose rather than a receptor, hydrolyzing this disaccharide into glucose and galactose for intestinal absorption. Lactase products are marketed in the United States as dietary supplements, which do not undergo FDA premarket approval for efficacy.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.