Meat, fish, eggs, nuts, milk and derivatives are all foods with a high content of noble proteins as they are rich in essential amino acids. Rice, wheat, cereals, legumes, contain a fair amount, while fruits and vegetables are foods lacking in this nutrient.
The nutritional quality of dietary proteins is expressed by a parameter known as Biological Value (VB). It depends on the greater or lesser content of essential amino acids in a food protein. The higher it is, the higher the quality of the proteins, which in this case are called noble proteins.
The efficiency and nutritional quality of food proteins was also evaluated in terms of their digestibility or assimilability. In fact, during digestion, some amino acids can be non-absorbed and eliminated with the faeces. This feature further influences the nutritional value of the food.
The protein that has a perfect balance between absorbed amino acids and eliminated amino acids has a Biological Value (V.B.) of 100 or higher. The reference food protein in this sense is that of egg which has a V.B. equal to 100%, whey protein has the highest V.B. equal to 104.
Casein, fish, beef
Source: Normal and Therapeutic Nutrition, 17th ed.
Animal or vegetable protein?
In general, we can define animal protein sources as noble, that is, with high biological value; it is enough to remember that the first protein source of life is represented by milk; less noble are the sources of vegetable proteins.
Cereals, for example, contain little lysine, while legumes are low in methionine.
However, the association of these two foods (e.g. pasta and legumes) is able to ensure the needs of the reciprocal amino acids, as the limiting amino acid of a protein, that is the one present in less quantity, is compensated by its greater availability. in the other; in this case, we speak of complementary proteins.
Diets that provide incomplete protein can lead to malnutrition. For this reason, the diet must be balanced, not only in terms of calories, but also in the qualitative composition of the foods that constitute it.
To learn more about the role and functions that proteins have in our body, go to this article.