Vegetable proteins 🆙

Introduction

Vegetable proteins are amino acid chains with specific biological functions but contained exclusively in cereals, legumes, pseudocereals, vegetables, fruit and oil seeds.

Before talking about vegetable proteins, let's review some very important concepts to establish the quality of a protein source.

What is there to know

Biological value (VB): represents the quantity of nitrogen actually absorbed and used net of urinary and faecal losses. The reference protein is that of the egg which has a VB equal to 100%

Protein efficiency ratio (PER): indicates weight gain in grams for each gram of protein ingested (3,1 for milk; 2,1 for soy)

Digestibility (D): ratio between ingested and absorbed nitrogen (in descending order wheat, milk and soy

Essential amino acids (AAE): The term essential indicates the body's inability to synthesize these amino acids from other amino acids through biochemical transformations. There are 20 amino acids involved in protein synthesis and among these 20 eight are essential [leucine, isoleucine and valine (BCAA), lysine, methionine, threonine, phenylalanine, tryptophan] during growth two other amino acids, arginine and histidine become essential

Chemical Index: it is given by the ratio between the quantity of a given amino acid in one gram of the protein in question and the quantity of the same amino acid in one gram of the biological reference protein (of the egg). The higher this index is, the greater the percentage of essential amino acids.

Limiting amino acid: represents that essential amino acid present in the lowest concentration compared to the requirement, this deficiency prevents optimal use of the other amino acids for protein synthesis.

Protein quality

In general the quality Protein of foods of animal origin is higher since they contain all the various essential amino acids. The lower quality of vegetable proteins is instead due to a lack of one or more essential amino acids. This amino acid, as we have seen, is called the limiting amino acid.

Cereals, for example, are deficient in tryptophan and lysine, an essential amino acid whose deficiency can lead to a deficiency of vitamin B3 (niacin). Legumes, very rich in decent quality proteins, are instead lacking in sulfur amino acids (methionine and cysteine) important for the growth of hair, hair and nails and for the synthesis of glutathione, a powerful antioxidant able to protect our cells from oxidative stress (free radicals).

However, by correctly combining different vegetable proteins, even alternating ones and not necessarily in the same meal, it is possible to compensate for the lack of various limiting amino acids. In this case we speak of mutual integration (or protein complementation).

Pasta and legumes is an example of an excellent combination since the amino acids that pasta is lacking are supplied by the beans and vice versa.

For further information: Amino Acid Profile of Foods

Essential amino acids and their sources of plant origin
Amino acid	Vegetable origin
Phenylalanine	Wheat germ
Isoleucina	Scarce sources available
Histidine	Wheat germ
Leucine	Wheat germ
Lysine	Various legumes
Methionine	Seeds in general, sunflower seeds, nuts
Threonine	Legumes, only marginally cereals
Tryptophan	Almonds, low in legumes and cereals
Valine	Wheat germ

Protein Associations
Plant foods	Limiting amino acid	Complementary food	Combination example
Wheat	Lysine, threonine	Legumes	Pasta and beans
Soy and other legumes	Methionine	Nuts and seeds	Soy and sesame
More	tryptophan, lysine	Legumes	Tortillas and beans
vegetable	Methionine	Nuts and seeds	Salad and nuts

Conclusions

In any case, it should be noted that all the concepts expressed so far must be interpreted rationally:

If it is true that vegetable proteins are deficient in some amino acids, it does not mean that these are not sufficient to cover the body's protein needs.
If it is true that the limiting amino acids prevent the optimal use of the other amino acids for protein synthesis, it does not mean that in these cases the protein synthesis is heavily compromised.
If it is true that the lack of combination of vegetable proteins can cause protein deficiencies in the long run, this is not valid in the short term. For example, if I dissociate cereals and legumes into two separate meals, the body is perfectly capable of regulating protein synthesis by implementing the limiting amino acids with those present in the endogenous reserves. If, on the other hand, only one type of vegetable protein is consumed for long periods of time (for example only cereals), the free amino acid stocks are "exhausted" and a protein deficiency inevitably occurs (negative nitrogen balance).

Therefore there are no particular contraindications in consuming mainly food of plant origin as it happens during the summer period. However, it is important that the diet includes the consumption of a wide class of foods of plant origin (dried fruit, vegetables, legumes, etc.) but also of some animal foods (eggs, milk, meats, etc.). In fact, an exclusively vegetarian diet, even if sufficient from a protein point of view, could be deficient in vitamins (B12) and minerals such as iodine, iron and calcium, and essential fatty acids.