Proteins are indispensable food for the construction of our organism, performing other important functions, such as protection ( antibodies ), catalysis ( enzymes ), regulation and growth ( hormones ), transport of oxygen (hemoglobin) and coagulation (fibrin ).
Vegetables have the ability to synthesize the 20 types of amino acids they need to make all their protein, which is not the case with animals.
Man, for example, is able to synthesize only 12 of these amino acids and is obligatorily dependent on the food to obtain the remaining 8. The latter (which we can not synthesize) are the so-called essential amino acids.
Therefore, in any diet , we must be concerned with the consumption of certain proteins that contain the essential amino acids in reasonable doses to ensure the synthesis of proteins essential for body building, growth and maintenance of vital functions.
Certain foods, such as meats, eggs and milk, contain many proteins rich in essential amino acids. So they can be our main sources of protein. They are foods of high biological or nutritional value. Plant proteins are poorer in essential amino acids, and their diversity is small.
As a consequence, the predominant or exclusive consumption of vegetables can lead to malnutrition, due to the lack of some types of amino acids. Rice, oats, beans and gelatine have low biological value because they provide us with few essential amino acids. This means that if someone wants to follow a vegetarian diet, it should be varied to provide the body with all the amino acids and other essential nutrients, such as vitamins and minerals.