Both gluten, a protein found in wheat and other cereal grains, and casein, a protein found in cow's milk, are common additives in processed foods. If your body reacts to gluten--with gluten sensitivity or a condition known as Celiac disease--or if you're allergic to casein, identifying and avoiding potential problem foods can save you from symptoms like diarrhea, weakness, fatigue, flatulence and abdominal bloating.
Grains
Wheat may be the best-known source of gluten, but barley, spelt and rye contain gluten, too. If you're reading labels, look not just for wheat, barley, spelt and rye but for ingredients derived from them. Malt, for example, is made from rye.
Wheat may also be listed under other names. Semolina, durum, bulgur, couscous, dinkle, spelt, farina, kamut, graham flour, matza and triticale are all types of wheat. Unless you're absolutely positive the ingredients you're looking at are gluten free, check for a gluten-free label to confirm that the food is safe for you. Usually if a product is gluten free, the manufacturer will announce it as obviously as possible.
Dairy
Casein is contained primarily in the curd, the part of milk that forms solid chunks when allowed to sour. But if you're allergic to casein, it's better to avoid dairy foods entirely. Dairy products include milk, yogurt, ice cream, cheese, cream and cream cheese derived from cow's milk. The casein in goat's and sheep's milk is slightly different chemically than that found in cow's milk and is tolerated by some people with casein sensitivity.
Processed Foods
Many processed and prepared foods may contain gluten, casein or both. Gluten is often added as a thickener to sauces, soups and fruit fillings. Some spices contain wheat powder to prevent clumping. According to Celiac Solution, some rice syrups may contain barley enzymes, and some mustards may contain wheat, which might not be listed on the label. Some types of soy sauce contain wheat. Chewing gum and candy bars may also have been dusted with wheat to keep them from sticking to the wrapper, and since this is considered a "packaging" element, it doesn't have to be listed on the label.
Casein may be added to processed foods as an emulsifier, to enrich protein content or to modify the texture, according to The World's Healthiest Foods website. Look out for casein as a possible ingredient in fortified cereals, high-protein drink mixes, breath mints, salad dressings, processed meats and infant formula.
