Because of the toxicity of cysteine, and possibly
even of methionine supplements given in excess, and the intrinsic problems associated with an induced amino acid imbalance, proteins rich in SAA have been considered as supplements. Immunocal®, a purified milk fraction enriched in whey protein is currently being used because of its potential to augment antioxidant defenses and improve immune function. Twenty grams/day of Immunocal significantly enhanced muscular performance and lymphocyte GSH in a group of 20 young adults.
Although whey proteins contain significantly more
cysteine than casein (2.5% vs. 0.35) the total amount of total SAA is less significantly different (5.2% vs. 3.2%).