What is lactose?
Lactose is a carbohydrate (natural sugar) found in all kinds of milk, including human milk.
What is lactose intolerance?
People who cannot easily digest lactose are said to have lactose intolerance. That's because they do not have enough lactase, an enzyme in the digestive system that helps to break down the lactose in food.
People with lactose intolerance can still digest some lactose, and 8-10g of lactose usually does not cause symptoms. This is the amount present in 175 to 200 mL (a small glass) of regular milk.