Effect of Methionine Restriction on Aging: Its Relationship to Oxidative Stress Homocysteine and methionine are key amino acids with a vital connection to glutathione one of your body's most important substances! Methionine is abundant in many foods, so protein isn't the culprit, Managing Competing Interests: Partitioning S between Glutathione and Protein Synthesis Plantae Frontiers Pathological role of methionine in the initiation and progression of biliary atresia protein synthesis protein intake. you can eat a pound of steak and only ~32% of those amino acids actually become new protein in your body. the rest gets converted to glucose