Amino acids are organic compounds that have in common a –NH2 (amino) group and a COOH (acid) group but are distinguished from each other by the side chain (R).
Amino acids are the constituent units of all proteins in our body, both structural ones (e.g. muscles) and those circulating in the blood (e.g. hemoglobin) and are the only macronutrients that, unlike sugars and fats, provide the nitrogen (N) necessary for metabolism.
How are they divided?
More than 500 different amino acids are known in nature but only about twenty are involved in protein synthesis. From a strictly clinical point of view they are classified into two main groups: essential amino acids (EAA) and non-essential amino acids (NEAA):
- essential amino acids: so called because the body cannot produce them independently but must necessarily introduce them with the diet.
- non-essential: they can be introduced with the diet but also form starting from the transformation of the same essentials in the presence of some substrates.
All proteins, both animal and vegetable, even those considered better from a nutritional point of view, contain a prevalent share of NEAA compared to EAA in the ratio of about 0.7-0.8. For this reason, during an illness or with advancing age, the decreased consumption and greater difficulty in digesting proteins lead to a lack of essential amino acids and the need to integrate them with the daily diet.
Amino acids: why does the human body need them?
To live, the human body must produce the amount of energy sufficient to deal with the continuous turnover of cellular structures. It is sufficient that a single essential amino acid is missing to prevent the synthesis of all the new proteins that contain it and undermine this delicate balance that keeps our metabolism efficient. Muscles represent the body’s largest protein reserve from which all other organs draw the necessary amino acids. For this reason, during illnesses, both acute and chronic, there is a more or less evident and dangerous consumption of muscle mass (sarcopenia). The loss of lean mass weakens the individual and worsens their quality of life, reduces their immune defenses and exposes them to a greater risk of infections and / or cancer.
Essential amino acids
There are nine essential amino acids (EAA): Leucine, Isoleucine, Valine, Histidine, Lysine, Threonine, Phenylalanine, Tryptophan, Methionine while there are eleven non-essential amino acids: Glycine, Glutamine, Serine, Cysteine, Arginine, Proline, Tyrosine, Asparagine, Alanine, Glutaminco Acid, Aspartic Acid.
The first three essential amino acids on the list are also called BCAAs or branched chain amino acids and represent about 35% of the amount present in skeletal muscles. Products based on BCAAs only exist on the market and are highly sought after in gyms, but it is a false belief that these alone can support muscle growth. The most recent studies show that three essential amino acids, however important, can never replace the specific functions of the other six.
Amino acids are essential to life as they perform multiple and complicated biological functions: energetic, structural and regulatory. The efficiency of the mitochondria, the cellular organelles where the necessary energy (ATP) for metabolism is produced, depends on an adequate presence of EAA. The formation of collagen, the most important protein of the skin, muscles, cartilage and bones, depends on EAAs. Tryptophan is essential for the synthesis of serotonin, a neurotransmitter important for mental health. Histidine is essential for the synthesis of hemoglobin, the protein that carries oxygen in tissues. Other amino acids strongly affect the synthesis of vitamins and glutathione, the main endogenous antioxidant.
Many do not remember that, until the beginning of the last century, in the populations of northern Italy, pellagra, a disease of nutritional origin that claimed thousands and thousands of victims every year. Over the years it was discovered that the onset of the disease depended on a dietary imbalance and in particular on a lack of tryptophan.
Today, the use of amino acids as dietary supplements has been studied in different areas, in chronic diseases, in aging and in sports. The very encouraging results obtained thanks to the use of some complete blends of all the EAAs has led many scholars to consider the research on amino acids one of the most encouraging in contributing to the fight against the main diseases of the Western world such as heart disease, cancer, diabetes, obesity and aging.