
Proteins provide 4 Kcal/g, so they are not very energetic components. They require higher caloric expenditure for metabolism and utilization than other nutrients. Proteins are the main structural elements of cells and tissues, and catalyze and regulate many reactions in the body.
Quantity and quality of proteins
An excessive intake of protein will result in its storage as fatty acids in adipose tissue. Conversely, a deficiency in protein intake is often associated with energy malnutrition.
When a subject does not ingest a sufficient amount of nutrients, he uses his energy reserves: first he consumes muscle and liver glycogen, then triglycerides stored in adipose tissue, and finally his muscle and visceral proteins.
In the case of protein, not only the quantity is important, but also the quality, that is, its biological value. In general, proteins from animal sources and legumes have a high biological value, while those from cereals and other vegetables have a low biological value.
However, one should not speak of the quality of the protein of an isolated food, since in the usual diet they are mixed with each other. Thus, if the combination of two foods supplies proteins that complement their deficient amino acids, the result is a better quality protein than if they are considered separately. Practical examples of a good supplementation are lentils and rice, lentils and potatoes, bread with milk, and, however, it is not a good protein combination lentils or chickpeas with meat.
Ana Rosa