Protein synthesis can occur only if all the amino acids are present, while if even only one is missing the process will stop. For this reason, the more the amino acid composition of a protein approaches that of the human body, the more it can be used (it is said that it has a high biological value). Conversely, when a protein is deficient in a given amino acid, it has a low biological value (because it is used less effectively in protein synthesis).
Amino acids, however, are not only involved in the processes of plastic type, ie construction and reconstruction, but also in those of energy production, such as the synthesis of sugars and fats. Our body is able, starting from different amino acids, to synthesize them, only some of them, called essential amino acids, must be introduced already pre-built with food.
The plastic function of proteins can be fully exercised only by the presence in the daily diet of all essential amino acids in the appropriate quantities.
To understand how proteins are essential for our body, just think that the loss of muscle mass due for example to sarcopenia (loss of lean body due to inactivity, overproduction of free radicals, seniority) begins to appear around the fourth decade of life (thus affecting a large part of the population and about half of the habitual users of the Gyms) leading to a loss of lean mass of 3-5% within 50 years; then 1-2% each year.
In many subjects muscle mass is halved by 75 years of age. Not to mention the … loss of strength: -40% from 30 to 80 years; loss of power (executive speed of a gesture): – 50% to 70 years compared to 20 years.
Result: functional activities compromised by loss of strength / muscle mass, reduction of energy expenditure at rest, reduction of tissue sensitivity to insulin, increase of subcutaneous / visceral fat, reduction of bone density (due to reduced mechanical stimulation on the bone, osteoporosis.
It is therefore clear how important it is to introduce a good daily protein quota, favoring complete proteins, and a constant and regular physical activity to slow down this deleterious physiological process.
Essential amino acids: leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
Non-essential amino acids: alanine, aspartic acid, cystine, glutamic acid, glycine, proline, serine, thyroxine, cysteine, arginine, histidine.
The proteins of animal origin (meat, fish, eggs, etc.) are complete, while the vegetable ones are incomplete, ie they are deficient in some essential amino acids: for example wheat, rice and corn are poor in Lysine.
In situations of incomplete nutrition or very intense athletic activity (especially when muscular work of strength or speed is required) it may be necessary to take complete protein supplements, ie containing all the amino acids.
Amino acids (or amino acids) are the primary structural unit of proteins. We can therefore imagine amino acids as bricks that, joined by an adhesive called a peptide bond, form a long sequence that gives rise to a protein.
Within the stomach and duodenum these bonds are broken and the individual amino acids reach the small intestine where they are absorbed as such and used by the organism.
From the chemical point of view, the amino acid is an organic compound containing a carboxylic group (COOH) and an amino group (NH2). In addition to these two groups each amino acid is distinguished from the others by the presence of a residue (R) also known as the side chain of the amino acid.
Classification of amino acids
In protein synthesis only twenty of the different amino acids existing in nature intervene (currently over five hundred). From the nutritional point of view these amino acids can be in turn divided into two large groups: one of essential amino acids and one of non-essential amino acids.
Those amino acids that the human organism can not synthesize in sufficient quantity to meet their needs are defined as essential. For the adult there are eight and more precisely: phenylalanine, isoleucine, lysine, leucine, methionine, threonine, tryptophan and valine. During the period of accretion to the eight remembered it should be added a ninth, histidine, in consideration of the fact that in this period the demands of this amino acid are higher than the capacity of synthesis.
Cysteine and tyrosine are considered semi-essential amino acids, as the organism can synthesize them starting from methionine and phenylalanine.
Essentially essential amino acids (arginine, glycine, glutamine, proline and taurine) are those amino acids that play a fundamental role in the maintenance of homeostasis and body functions in certain physiological situations. In some pathological conditions these amino acids can not be synthesized at a sufficient speed to cope with the real needs of the organism.
Arginine is assuming considerable importance, as a precursor of nitric oxide, for the many functions that the latter performs in cellular activity, in the transduction of biological signals and in immune defense.
CONTENT IN ESSENTIAL AMINOACIDS: those proteins containing all the essential AAs in quantity and in balanced relationships can be defined complete or noble. In general, animal proteins are complete and plant proteins are incomplete. The noble wording associated with plant proteins is not correct and has been introduced to counter the saying according to which “legumes are the flesh of the poor”. In fact, taking a good source of vegetable protein in the diet is very important and to further enhance this concept, the term “noble” has been improperly introduced. In any case, these deficiencies can be overcome simply by using appropriate food associations such as PASTA and BEANS. In this case we speak of mutual integration because the amino acids of which pasta is lacking are supplied by the beans and vice versa.
LIMITING AMINOACIDE: of a protein or of a protein mixture is the essential amino acid lacking or completely absent that limits the use of all the other amino acids even if present in excess of the needs. As we have seen in proteins of plant origin, this amino acid is generally not sufficient to guarantee the needs and must be introduced by combining it with other foods.
CHEMICAL INDEX: it is given by the ratio between the quantity of a given amino acid in one gram of the tested protein 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 will be.
RAMIFIED AMINO ACIDS: o BCAA are three essential amino acids (Valina, Isoleucine and Leucine) that in particular conditions, such as intense physical effort, are used as an auxiliary energy substratum for fats and carbohydrates.
- Taken before the effort, they help to preserve muscle tissue
- Taken before the effort, they give energy.
- Taken before the effort, they delay fatigue
- Taken after the effort they accelerate the regeneration of muscle tissue
- Taken after the effort they significantly improve recovery.
The branched chain amino acids (BCAA): leucine, isoleucine and valine, are essential amino acids that can not be synthesized by the body and which must be supplied by food. They occupy the third place among energy suppliers after carbon hydrates and fatty acids. They are essential for the proper functioning of muscle metabolism, just think that they alone represent 35% of muscle volume. Some research shows that even a moderate exercise increases the leucine requirement of the body by 240%.
At the muscular level they have a plastic / structural function by regulating protein synthesis in an anticatabolic and slightly anabolic sense. This effect is partly due to the ability to modulate the secretion of important hormones. Furthermore, always at the level of muscle tissue, the branched amino acids represent an alternative source of energy to carbohydrates. This energetic function begins with their transamination, and becomes important when the subject, after intense and prolonged effort, has a low availability of carbohydrates.
The transamination, which allows the energetic use of the branched is catalyzed by vitamin B6, this is the reason for the presence of this vitamin in the formulation of products containing branched amino acids. A third function of the BCAA is the possibility of mitigating the sense of fatigue in subjects subjected to intense and protracted muscular effort. This effect derives from the possibility of modulating the entry of tryptophan from the bloodstream to the brain.
At the central level, tryptophan is a precursor of serotonin, one of the biogenic amines potentially involved in the perception of fatigue. Taken together, the aforementioned physiological aspects of the branched amino acids suggest their use in sports to support intense muscular effort.
Taken before the effort can be an alternative source of energy if the body requires it. It also helps to mitigate the sense of fatigue in athletes not at the height of physical fitness.
The assumption after the race / training guarantees a better recovery especially if the physical stress induced attrition and microtrauma at the muscular level as happens for example in cross-country races or in series of exercises particularly challenging for the muscular masses.
They also have stimulating effects on the immune system: given to triathletes, they have increased the production of interleukin-2 and interferon after several intense efforts, counteracting the weakening of the immune system induced by training stress.
They also have an impact on the metabolism of glutamine. Athletes who take nutritional supplements with BCAA have virtually identical plasma glutamine rates before and after competition, while lowering 22.8% without integration. BCAAs also appear to be beneficial for sedentary people, by regulating the influence of tryptophan in the brain, which helps prevent the appearance of central fatigue.
Glutamine, an aminoacid called “Conditionally Essential” is the amino acid in the most abundant free form present in muscle tissue. It plays a vital role in the metabolism of proteins, in the construction and recovery of muscle tissue, in brain functions. It is also the primary energy source for intestinal cells and is essential for the optimization of immune functions … Recent scientific studies have indicated that glutamine can minimize or prevent muscle catabolism (destruction) in individuals suffering from metabolic disorders. One study found that subjects taking a Glutamine supplement had an increased lipolytic process (a greater mobilization of fat) than those taking placebo. During exercise the need for Glutamine appears to increase.
Recent studies have shown that physical exertion has a negative effect on the body’s Glutamine stores. Another study of healthy athletes engaged in intense anaerobic training showed a 45% drop in plasma Glutamine compared to their pre-training levels. In intense aerobic activity, on the other hand, the level of Glutamine in plasma dropped by 50%.
It has been proven that consuming small doses (about 2 grams) of free-form L-Glutamine may induce a 400% increase in the level of growth hormone (GH).
Functions of amino acids
The primary function of amino acids is to intervene in protein synthesis, necessary to cope with the cellular renewal processes of the organism. In addition to this function, called “plastic”, amino acids also have a modest but not negligible importance in energy production (branched amino acids)
Some amino acids are also precursors of compounds that perform important biological functions.
Niacin (vitamin PP), serotonin (neurotransmitter) and melatonin (regulating the circadian rhythms of the sleep / wake cycle) are obtained from tryptophan.
From the sulphured amino acids (methionine and cysteine) we obtain glutathione, an important antioxidant useful to fight free radicals and keratin, an essential protein for the health of hair and nails.
In addition to those involved in protein synthesis, many other amino acids perform very important functions. Among these, the best known in the sports field are creatine (useful for increasing capacity and anaerobic alactacid and lactacid power) and carnitine which facilitates the transport of lipids inside the mitochondrion).
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