If you have celiac disease, you know you need to avoid gluten (a protein found in wheat, rye, and barley) completely. You might also wonder if you need to avoid casein, which is a protein in milk, butter, and cheese.
There hasn’t been a lot of research on whether casein has the same effects as gluten. The theory got its start decades ago, when some people thought that casein, gluten, and autism might be linked. That theory isn’t proven.
Keep in mind that you could be sensitive to milk because lactose, which is the natural sugar in milk, upsets your stomach. Casein and lactose aren’t the same and your sensitivity may have nothing to do with casein. Anyone can have lactose intolerance, including both people who have celiac disease and people who don’t.
You can ask your doctor to test and see if you’re allergic to casein.
If you do need to go on a gluten-free, casein-free diet, you may want to work with a nutritionist to make sure you still get all the nutrients you need.
On a gluten-free diet, you’ll need to have other sources of B vitamins, iron, and fiber. You can do that through your diet, by choosing foods that are fortified with these nutrients, or through supplements.