The body utilizes 20 amino acids to produce its various tissues and molecules. The essential amino acids must come from the diet. The body cannot synthesize these amino acids. The non-essential amino acids can be produced by the body from other protein building blocks. Those amino acids marked by an asterisk are conditionally essential amino acids. These amino acids must be supplemented via a nutritional source if the body is under stress (illness, intense physical training, mental/emotional stress, genetic inefficiency) because the body cannot keep up its production due to excess demand.