Proteins are complex nitrogen containing compounds that are essential for the formation of all cells in the human body. Proteins are composed of chains of amino acids. The human body produces the majority of amino acids needed to form proteins, but some (the “essential amino acids”) are not produced by humans and must be obtained in the diet.
Fish, meat and other animal products are excellent sources of protein. Proteins are also found in fruit, vegetables and cereals, but individual fruits and vegetables may not contain all the essential amino acids necessary to maintain good nutrition. Thus, a variety of vegetables such as rice, cereals, corn, nuts and beans are necessary to obtain a balanced blend of proteins. Proteins are broken down in the upper gut by enzymes such as trypsin to amino acids and are then absorbed through the intestinal wall and into the bloodstream for further processing.
Doctors recommend that proteins should provide about 20% of our total daily energy intake, but average intake in the U.S. exceeds the recommended percentage. Excess protein ingestion leads to increased formation of amino acids in the body and these are converted into fats if not required for energy purposes. In contrast, deficient protein intake can lead to muscle weakness and fluid retention.