A shortage of one common nutrient could help cancer cells and viruses hide from the immune system. A Common Amino Acid With Major RolesArginine is used to build proteins and supports several other biological processes, including the removal of nitrogen waste. Scientists have long known that amino acid availability can alter metabolism and cellular signaling. “These findings are exciting because they reveal that consumption of a specific amino acid can directly regulate gene expression in an organism by increasing production of a protein enriched in that amino acid,” Tavazoie says. Mice fed a low-arginine diet developed more colon tumors, while those given more of the amino acid developed fewer.