These complex compounds are one of the most important ones in our body. They consist of many amino acids of which represents structural parts of the intracellular matrix, the cell membrane, transport system, coenzymes, antibodies, nucleic acids and many other molecules. They are important to us and for the normal cell function, its development, and reproduction. They are the “building blocks“ of all tissues.
These compounds are very important in providing the necessary energy and combustion of 1 g of these compounds release about 4 calories. The average content of these compounds in the body is about 15 % (e.g. an adult man who weighs 175 pounds has 27 pounds of these compounds in his body). Most of them are built into the skeletal muscles (43 %) and the skin (15 %).
Proteins are very complex compounds and usually contain hundreds of amino acids in a row, each connected by peptide bonds.
According to the number of amino acids in the chain, proteins are divided into:
The human body is unable to absorb (use) whole protein molecules from food (consisting of hundreds of amino acids). They first need to be broken down into amino acids (much smaller molecules) in order for our body can use them. Since through food we consume only proteins but not the amino acids, it is necessary to, first they decompose into amino acids in the body and under the action of different enzymes (mainly trypsin). After the decomposition of these compounds to amino acids in the stomach and intestine, amino acids are transported from the intestinal lumen into the intestinal wall where they are carried to all parts of the body.
The human body has no reserves of protein, and it gets them only through food. After the meal, amino acids that we have entered are used for the synthesis of new proteins the body needs. Between meals, if our body needs amino acids, protein in the tissues will be decomposed. As soon as you start with a meal, or as soon as the concentration of amino acids raise, the body receives a signal to stop the degradation of proteins in tissues and instead uses the incoming amino acids from food. As amino acid concentration taken from food decreases, so again starts protein decomposition in tissues. This state is called a state of "temporary starvation." The following meal breaks this state of "temporary starvation," and exactly on this process is based a physiological need for regular intake of meals.
If you skip your meal, then the state of "temporary starvation" goes into starvation and then our body in every way tries to prevent protein loss. This is why in this situation the need for glucose is reduced to a minimum. Oxidation of amino acids and urea excretion are also reduced. These processes also cause the reduction of "protein turnover" (the balance between the synthesis and degradation).
These compounds are very present in many foods both plant and animal origin considering that they are the most important components of all living cells. The structure of the chain of amino acids depends on the source from which it originates, and it is well known that proteins of animal origin (e.g. eggs, meat, and milk) are rich in essential amino acids and in quantities that meet the needs of an adult. Proteins from these sources are easily digested and have a high degree of utilization.
Plant sources do not contain a lot of essential amino acids, but an appropriate combination of plant foods can provide an adequate amino acid composition in the nutrition. Plant foods that are rich in essential amino acids are:
Wheat and rice are also rich in many essential amino acids, but they lack lysine, while corn lack tryptophan. On the other hand, vegetables have enough lysine but lack methionine (which can be found more in rice and wheat). Therefore, it is very important to make an appropriate combination of plant foods to ensure adequate intake of essential amino acids (especially vegetarians).
The advantage of this kind of nutrition is that you will reduce the intake of foods of animal origin that are high in fat and saturated fatty acids.
Protein needs depend on age, body weight, gender, and physical activity, and you can calculate recommended protein intake by using our calculator.
Proteins are molecules that have perhaps the greatest importance in our body. They consist of amino acids, which are divided into essential and non-essential, depending on whether the body can make them (non-essential) or have to be taken through food (essential). They should regularly be taken, every day, so it is recommended to take a larger part of proteins from plant sources, with moderate use of meat, eggs, and milk.