What is it?

A casein-free diet is an eating plan in which milk protein (casein) is eliminated by removing all dairy products and all foods containing casein from the diet. It is often, if not always, used in combination with a gluten-free diet, which calls for the elimination of wheat, barley, rye, oats, and any products made from these grains. Both diets are called elimination diets because a particular type of food is virtually eliminated from the child’s meals ⁽¹⁾.

Proponents of the casein-free diet say that many children with autism may have gastrointestinal difficulties that make it hard for them to digest milk protein properly. There are different possibilities for ways in which this could affect children with autism. The most studied theory is that eating or drinking milk protein leads to high levels of protein by-products, called casomorphines, in some children with autism. These by-products may then affect behavior like a drug would. Specifically, in these children, casomorphines could reduce their desire for social interaction, block pain messages, and increase confusion. If milk protein is taken out of the diet, the idea is that this will reduce the level of casomorphines, and behavior will improve as a result ^(2-4).