HOW TO ASSESS THE QUALITY OF PROTEINS CONTAINED IN A FOOD
Proteins are a fundamental component of our diet and are made up of amino acids. To simplify, we can imagine the amino acids as beads that form a necklace, this necklace is the basis of the protein structure.
We ourselves are made for 15-20% protein, because the tissues and many other body components are made of them. But not only that: many enzymes and hormones also have a protein structure. From all this we can understand the importance of proteins for the human body.
The proteins introduced with food are not used as such, but our body breaks them down into amino acids which they then reuse to build their proteins (or, secondarily, for other functions such as energy production). For the synthesis of the various body proteins, 20 different amino acids are needed, 8 of which (leucine, isoleucine, valine, lysine, tryptophan, methionine, phenylalanine, threonine) are defined as essential because the human organism is not capable of synthesizing them independently and therefore must introduce them with food. This suggests that not all the proteins we introduce with food have the same importance: those that contain all the 8 essential amino acids have a greater value because they provide us with what the body cannot produce independently.
Proteins containing essential amino acids are called noble proteins and are contained exclusively in foods of animal origin (meat, fish, eggs and dairy products). But those who have chosen to embrace a vegan diet should not worry, as it is possible to take the full range of essential amino acids by making a mix of various plant foods. A classic example is the combination of cereals and legumes (“pasta and beans”), in which the essential amino acids missing in cereals are contained in legumes and vice versa. The complementarity of the two foods makes eating pasta and beans become like eating a steak, with all the vegans pace!
A similar principle was also followed in the development of the BIVO formula.
In fact, it contains both cereals (eg oats) and legumes (eg peas). For this reason, even in BIVO all the 8 essential amino acids are contained, as evidenced by its amino acid profile.
The amino acid profile is a chemical analysis that is carried out in specialized laboratories and measures which and how many amino acids are present in a product.
The presence of all 8 essential amino acids is one of the most important parameters for assessing the quality of a protein, but other, equally important, factors need to be taken into consideration. The two best known and used are the chemical index and the biological value.
The chemical index is calculated by comparing the content of each essential amino acid contained in the protein part of a given food with their content in reference proteins. These reference proteins are, by convention, those contained in the egg because they are the most balanced. The maximum chemical index value that is equal to 100 is attributed to egg proteins. The greater the chemical index of a protein, the higher its quality.
The biological value, unlike the chemical index, measures how many of the proteins supplied by a given food are actually absorbed and used by the body. It is in fact almost impossible that all the proteins contained in a food are completely absorbed. The biological value is then calculated by making the ratio between the proteins used and the proteins absorbed by the body. For practical purposes, the ratio is actually carried out between nitrogen used and nitrogen absorbed, considering that nitrogen is supplied almost exclusively by proteins in the diet.
Also in this case, to obtain the final result, the value is compared
biological egg which is equal to 100.
To conclude, all these indexes are useful not only to establish the quality of proteins, but also to understand how important it is to vary protein sources as much as possible in the context of proper nutrition.
Bibliographic source: “Nutrition for physical exercise and sport.”, Michelangelo Giampietro, The Scientific Thought Publisher.
Paola Salgarelli, Nutritionist Biologist, specialist in Food Science