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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 or baking will not affect lactose.
Lactose, sometimes called milk sugar, is a carbohydrate that is made up of two different sugar molecules.
The disaccharide (di for two and saccharide for sugar) is made up of the two single sugar molecules, galactose and glucose. The bond that holds these two sugars together is broken by an enzyme called lactase and the disaccharide needs to be broken down into the two molecules so that they can be absorbed (our bodies only absorb single sugar molecules through the wall of the intestine).
The reason that many folks are lactose intolerant is because their bodies don't make the enzyme lactase. The lactose passes into the small intestine and is consumed by the bacteria in the large intestine who turn the sugars into water and carbon dioxide gas.
Cooking or baking will not break the bond and for those who don't have lactase it may mean that they will not be able to absorb the sugar.
Keep in mind that lactose intolerance can be dependent on the amount of lactose consumed. 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, CCMS