Branded whey protein powders will add casein to their products because studies show that whey and casein work better when taken together. Below are research articles on this topic.

Skeletal muscle is one of the largest organs in the human body. It is mainly composed of 70% water, about 22% protein, and about 8% fat, glycogen, nucleic acid and inorganic salts. Usually 500 grams of muscle contains about 110 grams of protein. If a bodybuilder wants to increase about 500 grams of lean body mass (fat-free body mass) in a week, he needs to add 15 grams of protein every day. Although the calculation is simple based on data, it is actually affected by many factors, such as digestion and absorption utilization, the types of protein supplements, and the timing of supplementation. But if you want to increase lean body mass, you must ensure sufficient energy supply on the basis of appropriate strength training, increase your calories by at least 200 to 400 kcal per day, and provide additional protein. In addition, you need to pay attention to corresponding vitamin supplements.

In terms of protein type, animal protein is usually better than plant protein. For example, milk is better than soy protein. Although the protein of the same quality is consumed, the essential amino acids consumed are different. In terms of protein, branched chain amino acids, especially leucine, are Supplementation is more conducive to protein synthesis, and its effect may be through stimulating insulin secretion and improving signal transmission related to protein translation.

The protein in milk is mainly composed of two major categories. Whey protein (whey) accounts for about 20% of the total protein in milk, and the other 80% is casein (casein). Whey protein contains a high concentration and appropriate proportion of essential amino acids, which is easily digested. The protein has a high bioavailability rate and is a fast protein. Casein is also rich in essential amino acids and combines important minerals such as calcium, phosphorus, iron, zinc, etc. However, casein is a large, hard, dense curd that is extremely difficult to digest and break down. It is a slow-release protein.

There has been a lot of research on these two proteins. Which protein is more beneficial? Some studies have found that whey protein is easier to digest and absorb. Within 1-2 hours after taking it, the amino acids contained in it quickly enter the blood circulation, and are digested within about 3-4 hours. Relatively speaking, the digestion and absorption of casein is relatively slow. It takes about one and a half hours after taking it for the amino acids contained in casein to gradually enter the blood. However, the digestion process is very long. Until 7 hours, the amino acids in casein are still stable. rate into the blood circulation.

Research on protein synthesis rate shows that 1 hour after taking whey protein, the protein synthesis rate in the body increases significantly, and returns to the level before taking it in about 3 hours. After taking casein, the protein synthesis rate in the body is within one and a half hours.There was a slight increase after 7 hours, and the degree of increase was lower than that of whey protein, but it could last for 7 hours, with a total increase of about 31% compared to before taking it.

In terms of protein decomposition in the body, after taking whey protein, the protein decomposition rate did not change and remained at the same level as before taking it. However, within 3-7 hours after taking casein protein, the protein decomposition rate was significantly lower than before taking it. A total of about 34% inhibition.

These studies suggest that whey protein is superior in promoting protein synthesis, while casein is slightly better in inhibiting protein degradation. We know that protein in the body always exists in a dynamic balance, constantly undergoing synthesis and decomposition at the same time. When synthesis is greater than decomposition, the protein content in the body increases, and more muscle tissue can be generated; when synthesis is less than decomposition, protein content in the body decreases. Muscle tissue may also be lost.

Therefore, when supplementing protein during exercise to build muscle, you should consider the characteristics of both, rather than choosing only one protein. To supplement protein before and after exercise, it is suitable to choose whey protein, and before going to bed after a day of training, you can choose casein protein to supplement in an appropriate amount. More often, whey protein and casein are mixed to achieve the effect of inhibiting decomposition and promoting synthesis.

References:

　1.Jose Antonio, Douglas Kalman, Jeffrey R, et al. Essentials of sports nutrition and supplements. HUMANA PRESS, 2008

2.Krista Austin. Performance nutrition applying the science of nutrition timing. Human Kinetics, 2011,2

3. Wang Lei, Cheng Xue, Mao Xueying Research progress on the biological functions of whey protein and its active peptides. China Agricultural Science and Technology Herald 2010, 12(5): 30-35

4. Guan Lu, Li Yuemin Whey protein and sports nutrition. Sichuan Sports Science 2003, 4