L-Theanine (LTA). a non-protein-derived amino acid. is isolated from tea and is used as dietary supplement or beverage ingredient. This study established an enterotoxigenic Escherichia coli (ETEC)-infected mouse model of oxidative stress to examine the antioxidative mechanisms of LTA in vivo. https://parisnaturalfoodes.shop/product-category/ketchup-no-sugar/