Glutamine

Glutamine is the most abundant free amino acid in plasma and skeletal muscle and a primary fuel for immune cells and enterocytes, positioning it at the interface of muscle metabolism and immune competence. A fall in glutamine availability has long been linked to the immunodepression and upper-respiratory infection risk seen with heavy training loads. Wenzel et al. (2026) measured salivary glutamine among the metabolites tracking exercise and recovery in a multi-omics strain model.