Casein is one of the two types of protein found in milk, the other being whey. Casein is a gel forming supplement. Whereas whey protein is considered “fast”, as it is rapidly digested, casein is a slow release protein that is digested over several hours. Due to this, casein is often taken before bed so it can be released gradually overnight.
So what are the benefits of casein protein?
Well, casein lasts longer in your system - it provides your bloodstream with a slow, steady flow of amino acids, which could last for hours. This is why it is best taken overnight, as it will be the most effective protein overnight than any other due to the slow release.
Furthermore, casein helps to improve metabolic rate. One study  that was conducted found that by increasing casein intake by 2 and 1/2 times, participants had a higher metabolic rate while sleeping. Metabolism is the number of calories the body needs while at rest. Therefore the higher your metabolic rate, the more calories your body will burn. This can be an advantage if your goal is weight loss.
Is your goal to increase strength? Good news, one study  found that casein protein had double the effect on strength results of the legs, chest and shoulders. The researchers believe this is because of casein’s anti-catabolic abilities. Anti-catabolic supplements such as casein prevent/reduce the breakdown of muscle.
But are there any drawbacks to casein?
The main negative side to casein is that people with dairy allergies may experience intolerance to casein, and it could produce an allergic reaction. Another con to consider is that it comes from an animal product. Animal products are thought to have a link with several medical conditions such as heart disease.