Protein is essential for the body and functions as enzymes, hormones, antibodies as well as transport and structural components.
There are 20 amino acids in human proteins, 12 are manufactured by the body and are known as “nonessential amino acids”. The remaining 8 are obtained from the diet and are termed “essential amino acids”.
Protein nutrition is based on a balance of essential amino acids and sufficient intake of nitrogen so the body can produce nonessential amino acids.
Complete protein foods
The nutritional quality of food protein varies and depends on essential amino acid composition. For example foods that contain essential amino acids at levels that facilitate repair and tissue growth are known as complete protein foods. These foods are also classified as having high biological value, which refers to an index in which all protein sources are compared with egg whites which provide the most complete protein and have the highest biological value of 100.
In general, foods with the highest biological value are from animal sources, such as eggs, milk, meat, poultry, and fish. However plant protein form a large part of the human diet, and are mostly deficient in 1 or more essential amino acids and are therefore regarded as “incomplete proteins”. Their protein quality however can be upgraded, by combining them with foods that are higher in protein quality or contain what ever essential amino acids are deficient.
For example, combining corn with beans results in a high quality protein food combination. Thus, the requirement for essential amino acids can be met in a vegetarian diet by mixing foods of complementary amino acids composition.
How much Protein does a body need?
The daily amount of protein your body needs is determined by energy needs, there are many situations in which extra protein is needed for example pregnancy, lactation, growth spurts and endurance training and other forms of physical activity.
Source: www.ralphrogers.co.uk Ralph Rogers