Lactose intolerance is an intolerance to the sugar in milk (not to be confused with a milk allergy, which is a reaction to the protein in milk.) The severity of symptoms depends on the amount of lactose consumed, and this varies from patient to patient. Some patients have problems with just 1 ml of milk, others can drink up to 100 ml before symptoms occur.

About 15-20% of the German population suffers from lactose intolerance.

Generally, lactose is broken down in the small intestine by the digestive enzyme lactase, and ends up in the blood where it is used as fuel. In patients with lactose intolerance, the enzyme lactase is either not produced, or not produced in sufficient quantities. When these patients drink milk, the lactose passes undigested into the large intestine, where it is broken down by bacteria. This process leads to intestinal gas. If more lactose is consumed than can be broken down by the bacteria, the patient experiences unpleasant symptoms including diarrhea, stomach pain, colic, bloating and nausea.

• Definition
• Causes and triggers
• Symptoms and effects
• Progression
• Diagnosis
• Therapy
• Tips