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Does cooking affect lactose? For example, will baked goods made with milk be OK for someone with lactose intolerance?
No. Cooking does not affect lactose.
Lactose is a sugar that is made up of two different sugar molecules. The disaccharide (di for two and saccharide for sugar) is made up of the two sugar molecules, galactose and glucose. The bond that holds these two sugars together is broken by an enzyme called lactase. The reason that many folks are lactose intolerant is because their bodies don't make the enzyme lactase.
Cooking or baking will not break the bond.
Keep in mind that lactose intolerance can be dependent on the amount that you eat. For instance, some people can tolerate the small amount of milk in baked goods or even a as much as a half a cup of milk over cereal. Because of the small amount in baked goods like muffins, this may be something you can tolerate. (For example, in my Banana Nut Muffins recipe there's about 1 teaspoon of buttermilk in each muffin.)
Timothy S. Harlan, MD, FACP