Nutritional needs: Focus on amino acids
Among the essential needs for the functioning of an organism are nutritional needs and the necessity of providing amino acids through food.
What is an amino acid?
An amino acid is a small quaternary molecule, composed of carbon (C), hydrogen (H), oxygen (O) and nitrogen (N).
Amino acids possess a carboxylic acid group (COOH) and have an amine function (NH2), hence their name amino acids .
There are several hundred amino acids in nature, but only a few are proteinogenic*.
*Proteinogenic: That which generates proteins.
“ Besides their proteinogenic role, amino acids (AAs) participate in the regulation of numerous intracellular biochemical pathways. This signaling role has been studied primarily in muscle, where certain AAs such as leucine and citrulline are particularly active in promoting protein synthesis.— (Clinical Nutrition and Metabolism, ISSN 0985-0562)”
Proteins are major components of our bodies and have many diverse functions:
- structural (such as collagen or keratin)
- enzymes (enzymes are proteins)
- participation in muscle contraction by being (e.g., titin) or non-contractile (e.g., myosin)
- hormonal (like insulin)
- transport (such as hemoglobin or lipoproteins)
What are proteinogenic amino acids?
Of the hundreds of existing amino acids, 22 are said to be proteinogenic.
There are 20 standard amino acids:
| Name | Code (3) | Code (1) |
|---|---|---|
| Alanine | To the | HAS |
| Arginine | Arg | R |
| Asparagine | Asn | N |
| Aspartate | Asp | D |
| Cysteine | Cys | C |
| Glutamate | Glue | E |
| Glutamine | Gln | Q |
| Glycine | Gly | G |
| Histidine | His | H |
| Isoleucine | Island | I |
| Leucine | Their | L |
| Lysine | Lily | K |
| Methionine | Met | M |
| Phenylalanine | Phe | F |
| Proline | Pro | P |
| Serine | Ser | S |
| Threonine | Thr | T |
| Tryptophan | Trp | W |
| Tyrosine | Tyr | Y |
| Valine | Val | V |
And 2 particular proteinogenic amino acids: pyrrolisine [Pyl, O] (only in arcuate) and selenocysteine (Sec, U).
Acids have two roles in the body:
- An energetic role thanks to their catabolism
- An anabolic role : synthesis of peptides and proteins
What is an essential amino acid?
As is the case for fatty acids, there are essential amino acids .
These amino acids must be obtained through diet because the body cannot synthesize them.
Non-essential amino acids can be synthesized by the body from other elements if they are present.
There are 9 essential amino acids in adults (11 in children):
- Phenylalanine
- Leucine
- Methionine
- Lysine
- Isoleucine
- Valine
- Threonine
- Tryptophan
- Histidine
There are 2 conditionally essential amino acids: Tyrosine and Cysteine.
In children, 2 additional amino acids are essential: Arginine and Glutamine.
What are the nutritional recommendations for proteins and amino acids?
EFSA and ANSES recommend a protein intake of 0.83g per kg of body weight for adults.
The WHO recommends daily intakes of essential amino acids:
| Amino acid | Intake in mg/kg |
|---|---|
| Phenylalanine | 25 |
| Leucine | 39 |
| Methionine | 15 |
| Lysine | 30 |
| Isoleucine | 20 |
| Valine | 26 |
| Threonine | 15 |
| Tryptophan | 4 |
| Histidine | 10 |
What are the different sources of amino acids?
Amino acids are present in all protein-containing foods, including animal products as well as plant-based products. However, there are some subtle differences.
Animal products do not pose a risk of amino acid deficiency. Eggs and whey, in particular, have a balanced amino acid profile. This is not the case with plant-based products.
Therefore, in the case of diets without animal products, such as the Vegan diet, it is important to ensure that a variety of foods are consumed.
The concept of a limiting amino acid
A limiting amino acid is an amino acid present in a smaller quantity in a food.
This limitation leads to a decrease in net protein utilization.
In short, the presence of a limited quantity of an amino acid will limit the use of proteins (and therefore other amino acids) in relation to the quantity of the limiting amino acid (the one in the smallest quantity).
The consumption of animal products does not lead to a risk of deficiency, however the consumption of plants and cereals which are subject to limitation can lead to deficiencies.
| Food | AA limiting |
|---|---|
| Wheat | Lysine |
| Rice | Lysine + Threonine |
| But | Tryptophan + Lysine |
| Peas | Methionine |
How can we overcome the amino acid limitations of certain foods?
These recommendations are especially valid in the context of a diet without animal products (vegan) or limited in animal products.
The simplest solution: Increase the intake! Increasing the food intake allows you to increase the intake of the limiting amino acid and therefore to be able to use a greater quantity of protein... But, this is not really ideal!
The ideal solution: As found in many traditional diets limited in meat intake, it is necessary to diversify food intake.
Diversification should be done in such a way that the limitations of one food are compensated for by another. Ideally, this should be achieved through a synergistic effect where each food compensates for the limitations of the other.
Around the world, traditional diets have adapted to the foods available. A classic combination is: cereal + legume .
Among the food combinations that can meet amino acid requirements are the following food pairs:
- Rice + Soy
- Rice + Lentils
- Rice + Beans (red, mung, azuki)
- Oats + Peas
- Wheat + chickpeas
- Wheat + Beans
In conclusion
It is essential to provide our bodies with amino acids. These are the building blocks needed to construct proteins. Some amino acids must be obtained through diet. To meet our amino acid needs, it's not necessary to eat meat or fish; a varied diet is crucial to avoid the negative effects of limiting amino acids.