Proteins are made up of long chained compounds called amino acids. When we eat proteins, their molecules are broken down into amino acids and peptides (which are compounds consisting of two or more amino acids) by various enzymes and acids within the gastro-intestinal tract. These amino acids and peptides are then absorbed into the bloodstream where they get to work, trading with the amino acids already in your cells and providing a continuous supply of replenishment for cellular growth and repair.
There are twenty different types of amino acids that humans need for healthy cell activity. Of these, there are nine amino acids that need to be obtained through your food because the body cannot produce them on its own (these are called “essential proteins”) and there are a further five amino acids that be produced naturally by the body (called “non-essential proteins”). There are six semi-essential amino acids that your body can usually synthesize however under certain conditions, like illness or stress, we might not be able to produce them and must therefore get them from your food.
The grouping of essential, semi-essential and non-essential amino acids does not mean that one group is more important than the others just that some need to be obtained through your diet.
Table 1. The Twenty Amino Acids
· Aspartic acid
· Glutamic acid
Source: bodybuilding.com, healthline
The entire number of amino acids available in the human body is referred to as your amino acid pool, which is typically around 120 to 130 grams in an adult male. This amino acid pool is transformed or exchanged about three to four times a day and so the body is continuously synthesising amino acids to maintain the correct amount. This is achieved partly through protein biosynthesis (where amino acids that are already in the bloodstream are reconstructed back into proteins) and partly through the absorption of amino acids from your diet. If some of the amino acids are not available in sufficient quantities, then the production of protein is weakened, and your metabolism may only function in a limited way.
Protein requirements vary greatly between individuals and so no two people will require the same amino acid levels to stay fit and healthy. And the quantity of semi-essential and non-essential amino acids produced by the body will depend on many individual biological factors, such as age, mental and physical stress.