Nitrogen is a characteristic of Amino Acids and therefore Protein. A Nitrogen Balance (Output-Input) is a way to understand this measure. First understand that of the 20 amino acids that make up proteins, 9 are considered essential as our bodies do not make them and 11 are considered non-essential as our body has the capacity to synthesize them- assuming they have the tools and parts to make that happen. In other words, and adequate intake of all amino acids is a good idea as our diets could easily be depleted of amino acids that are required to create the "non-essential" amino acids. Caveat: PKU, Lou Gehrig's, and other amino acid metabolism disorders are worsened by certain aminos.
BRANCHED CHAIN AMINO ACIDS (BCAAs)
Leucine, Valine and Isoleucine are notable as they are shown to assist the aged with Muscle Protein Synthesis (leucine notably) and they are also used for burn victims and have surfaced as potential cure for specific Autism (Journal Watch Psych). On a negative note there is also research that suggests Lou Gehrigs ALS from high concentrations of BCAAs in athletes (Experimental Neurology v. 228 issue 1.)
Proteins are given their backbone by amino acids. The highest Biological Value proteins are those that when eaten assimilate into our makeup to the highest percentage because of their amino acid profile. It is essentially Nitrogen Incorporated/ Nitrogen Absorbed from Ingestion--or simply, % of Nitrogen Utilized. Amino Acid Composition and Protein preparation affect the Biological Value of the protein. Think of Biological Value as how efficiently the body utilizes protein consumed. A food with a high Biological Value should possess a higher percentage of essential Amino Acids. Egg is the standard considered to have a perfect Amino Acid profile with a BV of 100.
- Egg 100
- Whey 104
- Milk 91
- Beef 80
- Casein 77
- Soy 74
Of the essential amino acids that we must gain from our diet, only some foods contain the "complete" set of essential amino acids. Typically meats, fish, egg, and dairy are complete with essential amino acids while some vegetable proteins are incomplete. Hemp Protein is an exception and is known as a complete protein. It is very important for active Vegetarians to understand this and incorporate proteins such as Hemp Protein in their diet.
PROTEIN TIMING AT MEALS
If we consume carbohydrates after exercise when glycogen stores are depleted, we enhance re-synthesis of glycogen stores. Similarly, upon finishing strength exhausting activities, protein is also beneficial through insulin--stimulated change in amino acid uptake and protein synthesis. Insulin and amino acid uptake spike (about 3 fold) after exercise and peak about 90 minutes after exercise. This can stimulate muscle growth and has repercussions for both the Athlete and the Aged (J Am Coll Nutr.) Indeed Protein following exercise provides a net Protein Balance to aid Muscle Development (www.jssm.org.)