Analysis of the amino acid profile of milk, an important supplier of essential amino acids with the Amino Acid Analyzer ARACUS
Lactoprotein is one of the main nutrients in milk, it is composed of 20 kinds of amino acids. Different amino acid ratios and arrangements form different types of proteins. Those proteins play an important role in maintaining the growth and renewal of body tissues, participating in various chemical reactions, and providing heat energy for physiological activities.
Proteins such as casein and whey proteins serve not only as nitrogen sources but also as carriers of bioactive peptides that influence metabolic pathways and immune responses (Korhonen & Pihlanto, 2006).
Lactoprotein is considered to be one of the proteins with the highest nutritional value. The main reason is that its amino acid content and composition ratio are basically close to the amount and ratio required by the human body for synthesis.
This makes milk proteins highly bioavailable, supporting anabolic processes, particularly during periods of growth, recovery, or malnutrition (Phillips, 2016).
The nutritional value of protein is measured by whether its amino acid composition is reasonable and complete. Amino acids can be divided into two categories: essential amino acids and non-essential amino acids according to needs of human body. The so-called essential amino acids refer to amino acids that are needed by the human body but cannot be synthesized by itself or the synthesis speed cannot meet the needs and need to be obtained from food. There are nine kinds of essential amino acids in human body, they are Leu、Ile、Lys、Met、Phe、Thr, Try, Val and His. Lactoprotein is rich in the above nine kinds of amino acids, but there are certain differences between different protein types. The content of essential amino acids contained in casein is 45.1 g/100 g, while whey protein is 50.9 g/100 g. Therefore, whey protein is recognized as the best protein by nutritionists.
In particular, whey protein is rapidly digestible and rich in branched-chain amino acids (BCAAs), which are known to stimulate muscle protein synthesis and enhance recovery after exercise (Tang et al., 2009).
According to the chemical scoring method, human milk and whole eggs score 100 points, milk scores 95 points, and whey protein scores as high as 104 points. The essential amino acid content of ideal protein and the recommended amount for 1-year-old children (1991) have proposed by FAO and WHO. Compare which with the content of essential amino acids in lactoprotein in milk, they are very close.
The high amino acid score of milk proteins reflects their excellent capacity to meet human nutritional requirements, particularly in early life stages (FAO/WHO/UNU, 2007).
Therefore, milk is considered to be one of the most nutritious foods. FAO and WHO have also proposed the daily requirement of essential amino acids for healthy adults. Suppose that an adult’s weight is 60 kg, then drinking 500 mL milk a day can meet his daily needs of essential amino acids except for Met + Cys.
This underlines the importance of milk in global nutrition programs and in addressing protein-energy malnutrition, especially in developing regions (Dror & Allen, 2014).
References:
- Korhonen H, Pihlanto A. “Bioactive peptides: Production and functionality.” Int Dairy J. 2006;16(9):945-960. doi:10.1016/j.idairyj.2005.10.012
- Phillips SM. “The impact of protein quality on the promotion of resistance exercise-induced changes in muscle mass.” Nutrients. 2016;8(4):211. doi:10.3390/nu8040211
- Tang JE, Moore DR, Kujbida GW, et al. “Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and after resistance exercise in young men.” J Appl Physiol. 2009;107(3):987-992. doi:10.1152/japplphysiol.00076.2009
- FAO/WHO/UNU. “Protein and amino acid requirements in human nutrition.” WHO Technical Report Series 935, 2007.
- Dror DK, Allen LH. “Dairy product intake in children and adolescents in developed countries: trends, nutritional contribution, and a review of association with health outcomes.” Nutr Rev. 2014;72(2):68-81. doi:10.1111/nure.12078