Lactose is the main carbohydrate in infant feeding, but its impact decreases as the child gets older and consumes less milk and dairy products. Congenital lactose intolerance is a very rare condition. However, lactase activity may be low and need to mature during the first weeks of life in many infants. However, the evidence that unabsorbed lactose is causing infantile crying and colic is contradictory. Unabsorbed lactose has a bifidogenic effect and improves calcium absorption. Lactose malabsorption may occur secondary and thus temporally to other etiologies such as infectious gastroenteritis, cow's milk allergy and celiac disease. One the cause is treated, lactase activity will gradually return to normal. The vast majority of Asian children will develop late onset congenital lactase deficiency. However, this entity only exceptionally causes symptoms before the age of 4-5 years. Symptoms are abdominal cramps, flatulence and watery, acid stools, and decrease the quality of life but lactose intolerance is not associated with "true disease". The diagnosis is made on clinical grounds and confirmed with a lactose breath test, if needed. These patients need to have a lifetime long reduced lactose intake to improve their quality of life.
乳糖是嬰兒主要的醣類來源，它的影響會隨著兒童年紀增長與牛奶及乳製品攝 取降低而遞減。先天性乳糖不耐症是一種很罕見的情形。許多嬰兒出生的第一 週，其乳糖酶活性可能較低，並需要時間逐漸成熟。然而，未被吸收的乳糖是 否是引起嬰兒哭鬧及絞痛的證據仍是矛盾的。未被吸收的乳糖可作為雙岐桿菌 生長之用，及促進鈣吸收。乳糖吸收不良也可能是次發性的，起因於其他暫時 的病因，如腸胃道感染、對牛奶過敏或乳糜瀉。一旦疾病被治癒，乳糖酶活性 會逐漸回復正常。亞洲兒童絕大多數為晚發型先天性乳糖酶缺乏症。但是，只 有少部分在4-5 歲前就有症狀。症狀為腹部絞痛、脹氣、水便或酸便及降低生 活品質，但乳糖不耐症與真正的疾病並無相關。如果需要，可經臨床表現及乳 糖呼吸測試確診。這些病人需要終身降低乳糖攝取，以改善他們的生活品質。.