Proteins, Their Role in the Human Body


What are proteins, How much do we need for them?

protein foods Proteins in daily food are important because they participate in the functioning of the body, its growth and reproduction. So proteins are components with a large number of molecules widely distributed in nature, which are integral parts of all living organisms.
– About 20 species of amino acids have been discovered
whose combination forms a large number
of various proteins in our body. Some of these
amino acids are essential or irreplaceable
and should definitely be consumed daily by means of
food because they cannot be synthesized in the human body.
Other amino acids are interchangeable and Can be synthesized in the body.

Essential amino acids: leucine, Valin, I soleucine, M etionine, Fenilalalin, Trezonin, Triozin, T ripofan, Lizin, Arxhini

Non-essential amino acids:
Glycine, Alanine, Prolin, Asparagine Acid, Glutaminic Acid, Serin, Cistein, Asparagin, Glutamine

The role of proteins in the body

* Proteins in the human body have different roles:
* Structural (building all the cells in our body),
* Regulator (a large number of hormones have protein composition),
* Carriers (hemoglobin and myoglobin are proteins),
* Enzymatic (building enzymatic systems in multiple metabolic pathways),
* Protective (antibody composition is protein),
Many other functional roles.

– By participating in the construction and functioning of every cell and tissue in our body, proteins make up about 20% of the total body weight.
From the point of view of sports medicine, it should be mentioned that proteins constitute the basic structure of:
a kujt Muscles (muscle contraction – actin and myosin in their composition are proteins),
b} Tethys (collagen and elastin as the basic constituents of tetiva are proteins),
c} Hemoglobin and myoglobin (representing oxygen transport proteins) etc.
The human body does not have protein reserves, so all proteins are structural and functional.
Protein is not a source of energy for our body, except when we have a complete lack of carbohydrates and fats, then amino acids are used as a source of energy.

Protein metabolism
Proteins in the body are constantly in dynamic metabolic balance, where they are regularly produced, broken down and converted.
Protein metabolism involves two processes: protein synthesis and protein breakdown. In the healthy human body there is a balance between protein synthesis and breakdown.
There are physiological moments when protein synthesis prevails over protein breakdown and these cases are:

1. Time of intensive growth and development in children and adolescents,
2. During the time of rest and treatment (from physical activity), after activities,
3. Increased muscle mass during sports activity (strength exercises).
– Pathological increase in protein synthesis in athletes can be done with banned doping substances, taking synthetic anabolic hormones such as testosterone and growth hormone that promote protein synthesis.

– The predominance of protein breakdown occurs during:
1. Intensity and duration of sports matches,
2. Improper diet in sports,
3. Adult diets that stay hungry,
4. Immobilization period during sports injuries.

Daily requirement for protein

– During feeding, proteins should be represented by 10-15% of the total daily energy needs. Of the proteins consumed through food, depending on age and activity, 1/3 to 1/2 should be of animal origin, because through them the needs for essential amino acids are compensated.
– It is important to know the amount of protein that proper nutrition should contain. This amount depends on the person’s diet and age. The daily human needs for protein without physical load for average daily activities are 1 gr per 1 kg body weight per day (1 gr / kg kg PT per day). Or, a person with an average weight of 75 kg needs 75 grams of protein during the day.
– The demand for protein in athletes is higher than 1.4-1.8 gr. in kg. body weight during the day. In sports with significant muscle mass (body building) the need for protein increases by 15-30 gr per day and on average is about 150 gr.
– The cells of the body have a certain limit for the deposition of proteins, they convert the excess into sugar, which then serves as a source of energy or fat that is deposited in adipose tissue, which ie. they no longer serve as building blocks for protein, according to the body’s energy needs.

What is the reason for the increase in protein needs in athletes?

– The reason for the increase in the need for protein in athletes is based on the following facts:
* Proteins are subject to breakdown during physical activity. This breakdown comes as a result of the reduction of contractile protein elements (contractile) in muscle fibers (actin and myosin) during muscle work, so their synthesis is necessary. This fact is very important for endurance sports, when we have a load over a long period of time and protein expenditure.

* In strong sports, respectively in sports with high intensity and short duration, there is a physiological stimulus for muscle growth and development, which creates opportunities and capacities for strength training with muscle contractions. For such opportunities, the muscles synthesize contractile structures (actin and myosin) which are proteins in the composition. Such a requirement is mainly emphasized in sports with pronounced muscle building (body building).

* Increased need for protein in people who are physically active regardless of type
activity is also the result of high metabolic processes required by physical activity and consisting in the prolonged synthesis of enzymes, hormones and other functional structures.

* During strenuous physical activity (running marathons), protein (among other things) also provides energy after depleting carbohydrate and fat reserves.

– Athletes with damage to the tendon-muscular system should receive larger amounts of protein due to the process of synthesis and formation of new tissues, which in terms of structure is mainly protein.

– With the introduction of proteins in the body in quantities above the optimal value, no major structural, functional or energetic effect will be achieved because our organs (liver, kidneys) do not have a large protein-enzymatic capacity for their metabolism. So only a certain and proper part will be used while the rest is thrown out of the body. Therefore, the presence of excessive amounts of protein in food is the reason for the increase in protein metabolites (breakdown of substances) such as urea, creatinine. and uric acid, which are spilled and simultaneously load and damage the kidneys.

– All studies show that excessive protein intake of more than 2 grams for body weight in an athlete is not necessary for muscle growth, because large amounts are excreted by the body and even has a negative impact on the health of the athlete. .
Conclusion: Protein intake should move around optimal limits because excessive amounts can do more harm than good to the body.

Influence on the type of sports activity on the amount of protein intake

– Medical-sports studies confirm that there is no specific change in the amount of protein intake depending on the type of sport. Thus, sports with endurance (low duration activity and intensity – aerobic type load) and sports with high intensity, short-term and high intensity sports activities (anaerobic type load), do not differ from each other for needs. . daily protein athletes.

– In particular, if in athletes engaged in sustainable sports activities, proteins are needed to compensate for the loss of protein expended by long-term and tedious physical activity. Unlike strength sports, proteins are needed for the new synthesis of the largest amounts of protein structures needed for the intensive training process and competitive processes.

– Finally, the amount of protein consumed each day is the same for both types of physical activity (endurance sports and strength sports). The only difference is in sports with weight lifting – body building, where demand increases by 30-40%.

Seed is important for protein metabolism in the sports organism

– During physical activity, our body consumes all the nutrients: carbohydrates, fats, proteins, water, minerals, vitamins, etc. Each of them has its own special function, with the exception of proteins.
– All other nutrients can be consumed during physical activity because at the same time they can be used and rebuilt (supplemented) because they create conditions for the development of energy metabolism which is the basis for exercise.
– During physical activity, proteins are consumed mainly as structural and functional substances, and as long as the exercises last, they cannot be rebuilt. During physical activity there is only protein breakdown.
– Now that physical activity is over, many processes begin where, in addition to rehydration, remineralization, regeneration and revitalization, processes of protein synthesis or protein metabolism occur. During this process, all spent functional and structural proteins are compensated and they are synthesized new, in order to preserve and increase sports opportunities.
– During physical activity (exercises), muscles can not use amino acids but only during relaxation from physical activity and in the period of adaptation to sports training.

– Conclusion: if protein breakdown prevails during the time of physical activity, then protein synthesis occurs during the relaxation of the body after physical activity and in the period of adaptation of sports training.

– It is considered that the normalization of protein metabolism is achieved in a time of 12-24 hours depending on the type of physical activity performed and the athlete’s condition.

The protein diet should prevail immediately after exercise and during rest time. There is no need to rely on protein foods before you start physical activity, nor during physical activity.

– By perfecting the sport technique itself and mastering the high physical preparation, three main elements related to protein metabolism are enabled:

1. Reduce protein breakdown during physical activity,

2. Expanding protein synthesis during rest time,

3. Accelerated protein synthesis during rest time after physical activity.

Protein energy value

– Now we know that proteins are not energetic substances for daily and sports activities. The role of proteins in the body is structural and functional. Only under conditions of complete depletion of carbohydrates and fats (exercises with intensity and duration, hunger), etc., Proteins break down as an energetic material. By breaking down 1 gr of protein, 4 kcal of energy is obtained.

– In sports nutrition, proteins participate with 10-20% of the total daily energy requirement. Consumption of 75gr of protein (daily requirement for protein) in non-athletes gives 300kcal of energy. Nutrition in sports with the required protein representation of 100-150 gr per day provides energy in the amount of 400-500 kcal.

– Mathematically calculated: 300 kcal per day from protein food to non-athletes consuming about 2000 kcal per day represent 10-20%. Whereas, 400-500 kcal per day from protein food to athletes, who for sports activities, have a demand of 3500 kcal per day also represents 10-20%.
– Based on this, it can be said that proteins participate with 10-20% of the total food demand in both non-athletes and athletes.

– From this we can conclude that proteins are not an important or qualitative source of energy for muscle contraction, so there is no need to rely on these energetic foods for athletes. Excessive protein intake in the diet mainly leads to increased physical and health condition of the body.

– Why proteins are represented by a lower percentage in food compared to carbohydrates (55-60)% and fats (20-30)%
1. Proteins, unlike carbohydrates and fats, do not serve as a source of energy, while for physical activity the main thing we need is energy.
2. One of the main reasons why proteins do not serve as an energy source is that their metabolism is very complex, specific and time consuming.
3. To carry out the process of metabolism of all substances (decomposition, transport, dissatisfaction, etc.), the body expends energy. to gain energy, we have to spend it.
– Much more energy is expended in the metabolic pathway of proteins than in the metabolism of carbohydrates and fats. Therefore, in addition to the amount needed for structural construction, we should not take more protein, because this means even the loss of energy for their metabolism.
Conclusion: the amount of protein that an organism needs to get is just that amount needed to maintain the body’s structural and functional abilities and not to gain energy.

Proteins in nutrition

-The protein quality of a food product is determined by the essential content of amino acids in them. In this way, proteins from various food products based on amino acid content are broken down into irreplaceable or essential and substitutable or essential substitutes for ammonoids.
-The protein we get from food can be of animal or plant origin. Animal-derived proteins are: meat, milk, eggs, have a high biological value (contain all essential amino acids) and with these must meet 2/3 of the protein needs.
– Proteins of plant origin (plant proteins, seeds, dried fruits, whole grains), etc., do not have enough essential amino acids and must meet 1/3 of the protein needs. It is good that in the diet of athletes, proteins are obtained in a combined composition: 2/3 of animal origin and 1/3 of plant origin.
– Proteins of animal origin are not only of high biological value, but also contain a high percentage of essential minerals such as Fe, Zn, K, etc. But proteins of animal origin also have negative sides. In their composition there are small or large amounts of saturated fats and cholesterol that pose a risk for overweight (overweight) and cardiovascular disease.

Biological value of proteins

Biological value of proteins
– The biological value of protein and the index of use by our body is different for different food products. The best proteins that can be used have an index of 100.
– Conclusion: Alkali protein content resists the combined method of food and more variety (protein of animal and plant origin).

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