Many people nowadays attach great importance to the amount of "nutrients" in their diet. When many foods are promoted, they often use the banner of "rich in high-quality protein" to attract consumers' attention. So what exactly is good protein? How are proteins good or bad?

First of all, we need to know that the basic building block of protein is amino acid. There are more than 20 kinds of amino acids that make up proteins in the biological body, of which 8 kinds of amino acids can not be synthesized by the human body and must be effectively supplied by food. These amino acids are called essential amino acids.

Most foods have eight essential amino acids, but the proportion of amino acids in the food is different, and the nutritional value of the protein will be different. Just like the eggs, milk and soy we often eat, these foods are rich in protein and the ratio of amino acids is very good for the human body. In addition, the more amino acids in protein can be used by the human body, indicating that it can meet the needs of the human body, the stronger the ability to ingested protein, only the proportion of amino acids and the needs of the human body to reach agreement, in order to be fully utilized, amino acids will not be too much waste. If the protein meets the amino acid composition and the composition of the human body's needs at the same time, and the efficiency of absorption and utilization by the human body is high, this protein can be called "high-quality protein" or "complete protein".

Some plant foods are also rich in protein, like rice, wheat and peas that we often eat, but the protein in these plant foods will have a relatively low proportion of one or two amino acids. If these foods are eaten alone, the efficiency of these amino acids to meet the needs of the human body will be relatively low, and it can be called "incomplete protein". Among the common food proteins, collagen is called "inferior protein" because it contains only seven essential amino acids.

However, when proteins contained in different foods are grouped together, the amino acids in them may complement each other, thus transforming poor quality protein into good quality protein. For example, the content of lysine in rice protein is very low, and the content of methionine and cysteine in the protein of mung beans and peas is very low, but rice is rich in methionine and cysteine, and peas and mung beans are rich in lysine, and the amino acids complement each other after they are combined, so it becomes a "high-quality" protein combination.

In general, after the human body obtains protein through food, various proteases will hydrolyze it to various amino acids, which are absorbed by the intestinal wall into the blood, and then re-synthesize the protein needed by the human body, thus making the human body healthier.