Casein is the main family of proteins found in cow’s milk. It makes up most of milk protein, while whey makes up a smaller portion. Casein digests more slowly than whey, which is why it is often marketed as a ‘slow’ protein.
Where do you get casein?
Dairy foods such as milk, yogurt, cottage cheese and cheese naturally contain casein. Casein powders are concentrated supplements made from milk proteins.
Casein vs whey
Both provide all essential amino acids and can support protein intake. Whey is digested faster, while casein forms a clot in the stomach and releases amino acids more gradually. For most people, total daily protein and overall diet matter more than choosing one over the other.
Is casein useful before bed?
Some athletes use casein in the evening because of its slower digestion, but you do not need a casein supplement to have adequate protein overnight. A normal protein-containing meal or dairy snack can also contribute.
Who should avoid it?
People with a milk-protein allergy should avoid casein. Lactose intolerance is different: some casein products may contain little lactose, but tolerance varies. Read labels carefully.
Which foods are naturally high in casein?
Milk, Greek yogurt, cottage cheese and many cheeses all contain casein because it is the dominant protein in cow’s milk. The exact protein amount varies by product, so check the nutrition label when comparing foods.
Does casein build muscle better than whey?
Neither protein automatically wins in every situation. Whey raises amino acids in the blood more quickly, while casein is digested more slowly. For long-term muscle gain, total daily protein, resistance training, energy intake and consistency matter more than choosing one protein source at every meal.
Is casein only for athletes?
No. Casein is simply a milk protein, so anyone who eats dairy may already consume it. Supplements are mainly a convenient way to add protein when food is impractical; they are not essential for most people who can meet their needs through meals.
Can casein upset your stomach?
Some people tolerate casein well and others do not. A true milk-protein allergy is different from lactose intolerance and requires avoidance of milk proteins. If a dairy product repeatedly causes digestive symptoms, review the ingredient list and discuss persistent symptoms with a healthcare professional.
The bottom line
Casein is a complete milk protein that digests more slowly than whey. It can be useful, but it is not mandatory before bed or after exercise. For total intake, see how much protein adults may need and our guide to protein in Greek yogurt.