Which enzyme deficiency is commonly associated with lactose intolerance?

• A. Lactase
• B. Maltase
• C. Sucrase
• D. Amylase

Answer: (A)

Lactose intolerance arises from a deficiency of lactase, the enzyme on the intestinal brush border that splits lactose into glucose and galactose for absorption. When lactase activity is low, lactose isn’t digested and instead passes into the colon where bacteria ferment it, leading to gas, bloating, and diarrhea. The other enzymes listed—maltase, sucrase, and amylase—act on different carbohydrates (maltose, sucrose, and starch, respectively), so their deficiencies would cause problems with those substrates rather than lactose. Thus, lactase is the enzyme deficiency associated with lactose intolerance.