Casein is in a family of phosphoproteins that make up 80% of the proteins in cow’s milk. In fact, casein is found in all mammalian milk in varying quantities, including human milk, where it constitutes 25-45% of proteins. It is a complete protein that supplies all the essential amino acids (those that can’t be synthesised naturally by the body: ).
The name ‘casein’ comes from the Latin word for cheese (‘caseus’) and, indeed, casein is a major ingredient in the production of this food. In cheese-making, the casein in milk from cows, goats or buffalo is typically coagulated into a protease using rennet. Prior to coagulation casein is often called ‘casiogen’ in the UK, whereas the term ‘casein’ is often reserved for the coagulated protein.
Casein is also commonly used as a food additive. It was historically used in artists’ paint and types of glue and plastics and still has a variety of diverse uses due to its binding properties and porosity, such as a binding for safety matches, an adhesive for labelling bottles and as an agent in the reminerlaization of tooth enamel in dentistry.
How do I know if I’m allergic to casein?
Lots of people are allergic to either, or both, the casein or whey proteins in milk, though young people are the most susceptible and most people outgrow it. A milk (casein or whey) allergy is different to lactose intolerance as the proteins trigger an immunogloben antibody response. Even a very small amount of casein can trigger an allergic response. What is the difference between a dairy (milk) allergy and lactose intolerance?
It is easy to diagnose in infants as generally symptoms will develop immediately after they start consuming milk formula, or after a child consumes food containing milk. In adults it can be more difficult to diagnose as we typically consume other foods simultaneously. A doctor may perform skin tests to detect the specific immunogloben antibodies that are responsible for triggering an immediate reaction, like skin rash, as well as look at your clinical history and suggest tests and challenges that isolate the suspect foods. Researchers claim that 1-7% of infants display an allergy to milk, and as many as 60% of those will overcome the allergy by the time they are four years old, 80% by the time they are six. Only 0.1-0.5% of adults have been found to have an allergy to milk.
Occasionally people with a milk allergy can consume pasteurised milk as the pasteurisation process breaks up the whey proteins (and they may only be allergic to whey, rather than casein proteins). Conversely, casein proteins are not broken down by heat so people who are allergic to it are likely to react to all milk products, however they are treated. Not all caseins behave in the same way after you consume them, and sometimes people who are allergic to the casein in cow’s milk can consume goat’s milk, for example, without having an adverse reaction because of the differences in the structure of the casein proteins.
Typical immediate symptoms of an allergy to casein include swelling of the face, mouth, tongue or throat, nasal congestion leading to a runny nose, sneezing, coughing and wheezing, itchy eyes, as well as red, itchy skin, rashes or hives. Other symptoms may take weeks to develop and include a general increase in mucous production, abdominal cramps, loose or bloody stools, and diarrhoea. The allergy can be severe enough to trigger anaphylaxis and so the best treatment is complete avoidance.
Most medical practitioners recommend replacing mammalian milk with soy milk if you are allergic to casein. It is important to ensure that you are still consuming all the essential amino acids that casein provides, but they are readily available in other foods too, such eggs for calcium and amino acids, or nuts and seeds (like brazil nuts and sesame seeds) for phosphorous.