Introduction
Vegetable proteins are chains of amino acids with specific biological functions but contained exclusively in cereals , legumes, pseudo-cereals, vegetables , fruit and oilseeds.
What You Need to Know
Biological Value (VB): represents the amount of nitrogen actually absorbed and used net of urinary and faecal losses. The reference protein is that of the egg which has a BV equal to 100%
Protein efficiency ratio (PER): indicates the 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 eight of these 20 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 a gram of the protein under examination and the quantity of the same amino acid in a gram of the biological reference protein (of the egg). The higher this index is, the higher the percentage of essential amino acids will be .
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 protein quality of foods of animal origin is superior since they contain all the various essential amino acids. The inferior 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.
For example, cereals 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 moderate quality proteins, are instead deficient in sulfur amino acids (methionine and cysteine) which are 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 and not necessarily in the same meal, the deficiency of the various limiting amino acids can be compensated. 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 beans and vice versa.
| Essential amino acids and their sources of vegetable origin | |
| Amino acid | Vegetable origin |
| Phenylalanine | Wheat germ |
| Isoleucine | 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 | |||
| Vegetable foods | limiting amino acid | Complementary food | Combination example |
| Wheat | Lysine, threonine | Legumes | Pasta and beans |
| Soy and other legumes | Methionine | Dried fruit and seeds | Soy and sesame |
| Corn | Tryptophan, lysine | Legumes | Tortillas and beans |
| Vegetables | Methionine | Dried fruit 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, this does not mean that they are not sufficient to cover the body’s protein requirements.
- If it is true that the limiting amino acids prevent the optimal use of the other amino acids for protein synthesis, this does not mean that in these cases protein synthesis is heavily compromised.
- While it is true that the lack of combination of vegetable proteins can cause protein deficiencies in the long run, this argument is not valid in the short term. If, for example, I dissociate cereals and legumes in 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 stocks of free amino acids are “exhausted” and one inevitably runs into a protein deficiency ( negative nitrogen balance ).
Therefore there are no particular contraindications in consuming mainly foods of plant origin as happens during the summer. However, it is important that the diet includes the consumption of a vast class of foods of plant origin (dried fruit, vegetables , legumes, etc.) but also of some animal foods ( eggs , milk, meat , 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.
Do you want vegetable proteins?
Enter the vegan recipes section and discover many tasty alternatives to animal proteins :
- Homemade seitan
- Homemade mopur
- Homemade wheat muscle
- Homemade tempeh
- Vegetable fillet with green pepper
- Vegetable escalopes with mushrooms
- Aubergine meatballs and vegetable meat
- Chickpeas Hamburger
- Vegetable cheeses
- All recipes based on vegetable meat.
