Lactose is a sugar found in milk, dairy products, and in some quantities in milk-derived products.  Lactose is used as a food additive to enhance texture, flavor, and adhesive qualities.

Health considerations

Lactose maldigestion occurs when there is a deficiency or complete absence of the enzyme lactase in the lining of the small intestine. Lactase is necessary for the breakdown of lactose into the sugars, glucose and galactose. In its absence, lactose passes into the colon where it is fermented and produces gas. Lactose intolerance is the coupling of maldigestion and physical symptoms including abdominal bloating, diarrhea, and nausea. Prevalence varies around the world and is more common in some ethnic groups.

Keep in mind

Labeling of milk as an ingredient, not a contaminant, is mandatory, though labelling of lactose itself is not.

May be found in

Butter, margarine, milk, dairy byproducts


Genetics Home Reference
Medline Plus

Aternative Spellings and Names

Milk sugar

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