If you have sensitivities to dairy products, you may be wondering whether you need to look for lactose-free foods, casein-free foods, or both. As it turns out, lactose and casein are completely separate components of dairy, and just because you react to one doesn't mean you'll react to the other.
Lactose is the chemical name for milk sugar, a carbohydrate that has a structure not unlike that of table sugar, or sucrose. Like sucrose, lactose is a disaccharide, meaning it's made up of two separate sugar units, or monosaccharides. Specifically, lactose consists of glucose, a ubiquitous sugar in nature, and galactose, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." When you consume lactose, you have to digest it into its component monosaccharides before you can absorb them.
Casein, unlike lactose, is a protein. It's made up of smaller building block molecules called amino acids, and when you consume dairy, you break the casein down into these component units and absorb them into the bloodstream. There are several different proteins in milk; casein is only one of them. Specifically, casein is the protein that tends to solidify into clumps during the process of fermentation, as in cheese making.
Intolerance and Allergy
If you have difficulty consuming milk, you may have an intolerance or allergy. Lactose intolerance occurs as a result of insufficient lactase production, where lactase is the enzyme you use to digest lactose, explain Drs. Mary Campell and Shawn Farrell in their book "Biochemistry." Symptoms of lactose intolerance include gastric discomfort and gas. Alternately, you might have a casein allergy, which is much more serious. Symptoms can include difficulty breathing and hives.
Purchasing Appropriate Foods
If you have trouble with lactose intolerance, you'll need to shop for lactose-free milk and dairy products, and make sure the other foods you buy are lactose-free. To make lactose-free milk, manufacturers react the milk with lactase, which pre-digests the lactose. It's not possible to obtain casein-free milk, however; the casein is inextricable from the dairy. If you're allergic to casein, ensure that the foods you buy are casein free, and don't contain the protein as an additive.