The Role of Protein in the Body

10 Feb 2012, by Dr. Marnie Wachtler in Nutrition

Protein is an essential component of human life, making up some 20 per cent of our total body weight. It is a significant constituent of all body cells, functioning both in their growth, as well as maintenance and repair. Additionally, protein acts as a regulatory substance, involving most of the body’s required functions: from antibodies to enzymes, and many hormones.

The Building Blocks

Protein is made of up chains of amino acids, linked together in specific sequences predetermined by our genes. The order, and number of amino acids determine the specific role a particular protein plays in the body. There are a total of 22 amino acids, 13 of which can be manufactured by the body on its own. The remaining 9 do not occur naturally, and are provided from dietary sources. It is for this reason that dietary protein is so important for the normal functioning of many bodily processes. The 9 essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
From a dietary standpoint, all protein is not alike. Nutritionists generally describe dietary protein as either complete or incomplete. That is, either it contains the 9, so-called essential amino acids, or it does not. We cannot survive on incomplete protein alone because, by definition, one or more of the 9 essential amino acids are missing… and all are required for the complete synthesis of the body’s required protein.

The Source

Complete protein is generally found in animal foods, including meat, fish, poultry, and dairy products. Protein from many common vegetable foodstuffs, such as grains and various types of beans, is of the incomplete variety. It is possible to combine certain incomplete protein with other incomplete protein and, if consumed in the same meal, let the body manufacture the missing essential amino acids. So, strictly speaking, a true vegetarian can get by without eating animal products… if they know exactly what they are doing, and how to combine incomplete protein from “complementary” food sources.


How Much is Enough?

What happens if you do not consume enough protein containing all of the required amino acids? Your body will be missing one or more of the essential building blocks and you will begin to suffer muscle and tissue loss and, if prolonged, critical bodily functions will break down.