Casein protein (pronounced kay-seen) is the predominant protein found in milk. It makes up about 80% of the protein in cow’s milk, while the remaining 20% of protein in milk is whey. Casein protein is extracted from the milk through ultra filtration, without the use of chemicals. This process increases the amount of bioactive milk peptides that support immune function as well as enhance muscle growth. Casein protein has an excellent amino acid profile and is primarily known as an extremely slow-digesting protein.

Casein protein is a slow-digesting protein because it forms a “gel” in the gut, which results in a steady release of amino acids into the blood stream over time. Research shows that when you consume casein, you will reach a peak in blood amino acids and protein synthesis between three to four hours. The total release of amino acids in the bloodstream, however, can last as long as 7 hours after ingestion of casein protein! Whey protein, in comparison, reaches a peak in blood amino acids and protein synthesis in about forty minutes and the total release ends in about an hour.

Since casein protein slowly enters the blood stream, it has very little impact on protein synthesis. It has a powerful effect, however, in suppressing protein breakdown. In other words, it’s an awesome muscle-sparing protein. Muscle growth is dependent on the balance of protein synthesis and protein breakdown. To tip the balance in your favor, you want to increase protein synthesis and decrease protein breakdown. You can achieve this by supplementing with whey protein (fast absorption/promotes protein synthesis) and casein protein (slow absorption/suppresses protein breakdown).

To effectively take advantage of whey and casein proteins, you need to use them at the right times of the day. Casein protein is the only protein you should be taking before going to sleep. The reason is because your body needs to be sustained for six to eight hours during your sleep without food. You don’t want your hard-earned muscle being broken down in your sleep, so a protein that is slowly released over time is best. If you took whey protein before going to bed, it would do very little since whey is absorbed and used within an hour.

Whey protein should be used first thing in the morning and after workouts. If you have to go more than three hours without food during the day or are taking a protein shake as a meal replacement, you should use a blend of whey and casein – about 50/50. This will give you a quick shot of protein and a sustained release of protein to carry you through to your next meal. Finally, if you are eating every two to three hours, you can use whey protein by itself in between meals.

There are three forms of casein protein: calcium caseinate, micellar casein and milk protein isolate. Calcium caseinate is the lowest quality among the three forms and is commonly used as a food ingredient. Micellar casein and the casein in milk protein isolate are identical. While micellar casein is 100% casein, milk protein isolate has both micellar protein and whey. As a result, milk protein isolate is a more economical choice between the two.

Like whey protein, not all milk protein isolates are created equal. Some supplement companies sell inferior milk protein isolate products (will have less casein and more whey protein). The best milk protein isolates have around 80% micellar casein and 20% whey.  In case you’re wondering, you can get the same casein/whey ratio found in the highest quality milk protein isolates by just enjoying a glass of milk! Remember, milk is 80% casein and 20% whey – just like the highest quality milk protein isolates have. One eight ounce glass of milk, however, has only 6.4 grams of casein, while one small scoop of a high quality milk protein isolate will have over 20 grams of casein protein! Mix your milk protein isolate in milk to get the most casein protein for your buck!

There are many “sustained release protein” products on the market, but be careful before you buy as you may not be getting what you think. As previously mentioned, if you are looking at purchasing a milk isolate protein product, some supplement companies may be using an inferior isolate. In addition, many supplement companies want to avoid using too much casein protein in their products because it is more expensive than whey to produce and has a distinct “chalky”, or “malty” taste which many find unpleasant.

Supplement companies know that casein proteins are very popular among bodybuilders and athletes so they may go to extraordinary lengths to make their products appear as though they contain more casein protein than they actually do. Don’t let their marketing hype fool you. Pay close attention to the ingredients. Products that are high in casein protein will have miscellar protein, milk protein isolate or some form of casein as the first ingredient.

You also want to pay attention to the different protein sources they use. The more protein sources used, the less casein protein there may actually be in the product. For example, a product with just two protein sources – milk protein isolate and whey protein concentrate will most likely have more casein protein overall than a product that contains multiple protein sources such as milk protein isolate, whey protein concentrate, egg protein and soy protein. The more protein sources they use, the more “watered-down” the casein content may be.

There are a couple sustained release protein supplements I recommend.  They are Optimum Nutrition 100% Casein Protein and Xtreme Formulations Ultra Peptide. HSN Advanced Driver is also good if you can locate it - it's been discontinued. For some reason though, HSN promotes their product as being a terrific post-workout protein supplement. I’m not so sure I agree with them because there are no quick absorbing proteins (i.e. whey) in their product, which is what you want after a workout. Despite their marketing hype, I would not recommend using this product as your primary post-workout protein. The only kind of protein you want after a workout is whey! One negative about this product is that it does use calcium caseinate as one if its protein sources, which is the lowest quality casein protein. Still though, it’s a good overall slow release protein.

Optimum Nutrition 100% Casein Protein is arguably my favorite out of the 3. Optimum has always been known for providing a good solid product that delivers what it promises. That being said, they've done a great job with this product as well. It's a few dollars more expensive than the others, but it's worth the extra cost. It's a great slow release product for use as a post-workout. With 24g of proteins, over 9g of BCAAs, and a low 3g of carbs, this will be a great post workout for almost anyone, no matter your body composition or age.
Xtreme Formulations Ultra Peptide is a few dollars cheaper than Advanced Driver and gives you one more gram of protein per serving. Even better, it contains solely high quality protein sources (micellar protein, whey protein isolate and milk protein isolate). Either way, Optimum, Advanced Driver or Ultra Peptide are slow release proteins worth trying.

Regardless of what casein protein supplements you buy, look closely at the labels and make sure you are getting what you are paying for!