患有乳糖不耐症的成人和少见的婴儿患者因为缺乏可将乳糖分解为单醣的,所以无法消化乳糖,并且当吃进含有乳糖的食物后便会有腹泻和腹胀的症状出现。

• "Lactose-intolerant adults, and more rarely infants, cannot digest lactose because they lack the enzyme (lactase) that splits it into simpler sugars and suffer diarrhea and Bloating when they eat foods containing it."