Protein is the only macronutrient that promotes lean tissue growth (anabolism). In other words, to grow muscle you need protein! Protein also has other important functions in the body beyond building muscle. Those functions include: building and repairing blood, bones, teeth, skin, hair, nails, and your internal organs, provides immune protection and can provide a source of energy (when there is excess dietary protein or inadequate dietary fat and carbohydrate). As you can see, protein is an extremely important nutrient for good health. In fact, the word protein comes from a Greek word meaning "of primary importance."

Proteins & Amino Acids
Proteins are highly complex molecules comprised of linked amino acids. Amino acids link together to form chains called peptides. There are 20 or so amino acids that make up protein - eight are essential (body can't make them on its own). Those essential eight are: leucine, isoleucine, valine, threonine, methionine, phenylalanine, tryptophan, and lysine. Another amino acid, histidine, is considered semi-essential because the body does not always require dietary sources of it.

The non-essential amino acids can be made from the essential amino acids. The non-essential amino acids include: alanine, arginine, aspartic acid, cystine, glutamic acid, glycine, hydroxyproline, proline, serine and tyrosine. Conditionally essential amino acids, so named because during certain periods, such as infancy or certain metabolic states, can be considered essential for that period of time.

There are also branch chain amino acids (BCAA). They are named "branch chain" because they branch off another chain of atoms rather than form a straight line as other amino acids. The branch chain amino acids are leucine, valine and iso-leucine. These are used (oxidized) during exercise and make up to one third of the amino acids in muscle tissue. They play a critical role in the turn over of lean body tissues (muscle) and is muscle sparing (i.e. anti-catabolic) in a variety of muscles wasting states. L-leucine appears to be the most important to preserving hard earned muscle mass; intense exercise and certain disease states have been shown to eat up a great deal of L-leucine. Proteins, specifically whey protein, is very high in BCAA's.

Complete Proteins
Different foods contain different proteins, each with their own unique amino acid composition. The proportions of essential amino acids in foods may differ from the proportions needed by the body to make proteins. For instance, unlike animal proteins, plant proteins may not contain all the essential amino acids in the necessary proportions. The proportion of each of the essential amino acids in foods containing protein determines the quality of that protein. Dietary proteins with all the essential amino acids in the proportions required by the body are said to be a complete protein. Complete proteins include whey, egg, meat, fish, milk and cheese.

Proteins are ranked according to Biological Values (BV), arbitrary numbers given to protein to show comparisons in their availability within the body. At the time the system was introduced eggs were given the highest BV of 100 because they are the most bio-available natural protein. Afterwards whey was isolated from milk and shown to have a higher BV, and depending on the process used can yield percentage from 104 to 154 on the scale. The top ranked proteins include:

• Whey Protein Isolate = 157
• Whey Protein Concentrate = 104
• Whole Egg (yolk & egg white) = 100
• Milk = 91
• Egg White = 88
• Meats = 80
• Casein = 77
• Soy = 74

Click here to read Part 2:  Incomplete Proteins