There are 8 grams of protein in a cup of milk. This includes both types of protein found in dairy products, casein and whey. Casein provides 80 percent of the total protein, while whey provides the remaining 20 percent.
The total amount of protein varies slightly depending on the type of cow. Milk from Jersey and Guernsey cows contains the highest amount of protein, while Ayrshire and Brown Swiss breeds produce milk with the lowest amounts. Additionally, milk produced in the summer tends to contain slightly less protein than the milk produced in the colder months. Because it is loaded with essential amino acids and is easily digestible by most people, milk is considered a higher quality protein than beef, soy and wheat products.