Protein.
Proteins are complex organic macro-molecules which present a linear  chain-like structure and they are consisted of basic elements known as amino acids. The latest are the most fundamental ingredients of life.
In humans, protein is the most important nutrient, since after being ingested and metabolized, it can provide nitrogen and essential amino acids. The latest, in turn, are used in the synthesis of non-essential amino acids and a wide range of various types of other proteins respectively, according to the body's functional needs. These needs vary depending on gender, age, weight, daily physical activity and health state.
Proteins are found in muscles, skin and organs and they are vital for body growth and development. They are present in blood and all other fluids, apart from urine and bile. Proteins are absolutely necessary for a huge range of bodily biochemical reactions. Certain types of proteins, such enzymes and hormones, trigger or regulate metabolic functions. Antibodies are defensive proteins that contribute to optimal immunity. Collagen is the most abundant protein in the body and provides shape and structure to organs. Hemoglobin is the protein which is contained in red blood cells and plays a key role in transfer of oxygen from the lungs to other organs.
As soon as dietary protein is ingested, brakes down to polypeptides which, in turn, can give amino acids. Vitamin B6 contributes to protein digestion. Thus, the higher the protein intake, the more the need for vitamin B6 is. Ammonia is the by-product of protein catabolism and it converts to urea or uric acid.
Proteins are often the causes of allergic reactions to certain foods. This happens because, in some people, certain proteins are not recognized as beneficial and trigger the reaction of the immune system. For instance, casein in milk, gluten in grains or proteins found in peanuts and in seafood can cause adverse allergic reactions.
Protein food sources.
As it has been explained already, amino acids are the basic structural elements of proteins. Peptides are more complicated biochemical structures and they are consisted of certain numbers of amino acids. Amino acids are classified as non-essential and essential ones, depending on whether they can be produced within the body or not. The body needs twenty two amino acids to manufacture its own proteins. Humans are self-sufficient to only thirteen amino acids. These are the so-called non-essential amino acids, since the body can synthesize  them and they do not need to be obtained from dietary sources. On the contrary, nine amino acids are essential and they have to be taken with foods. Threonine, valine, tryptophan, isoleucine, leucine, lysine, histidine, phenylalanine, and methionine are the essential amino acids. Although arginine is not considered essential it is required for infants, seniors and people with intense body training, especially bodybuilders.
If a dietary protein can provide adequate amount and a full range of essential amino acids, it is characterized as a complete protein. Otherwise, it is called incomplete protein.
All dietary sources of animal origin, such as meat, fish, shellfish, eggs and dairy products include complete proteins, whereas plant foods can provide only incomplete proteins.
Studies have shown that 25gr daily intake of soy protein can provide high protection against heart coronary disease.
A balanced, healthy diet can easily supply all the essential amino acids. 
Deficiency in protein.
Protein deficiency is difficult to occur, since this macro-nutrient is found in abundance in dietary sources. Vegetarians can easily prevent deficiency by eating a wide variety of plant foods, since each incomplete protein contains different kinds of amino acids.
Protein deficiency can lead to symptoms such as fatigue, insulin resistance, hair loss and depigmentation, muscle waste, low temperature, hormonal fluctuations and loss of skin elasticity. Severe protein deficiency that occurs only in famine conditions is fatal.
Protein excessive intake.
Excessive protein intake has been associated with calcium depletion which, in turn, can result in bone loss and a lot of strain on kidneys. Liver dysfunction may occur, as well. |
