A method for improving adsorption of amino acids in a vertebrate, including mammal and bird, is included. The method comprises administering to a vertebrate, including mammal and bird, in a sufficient amount and/or at a sufficient rate to enable desire effect. AKG, AKG derivatives or metabolites, AKG analogues or mixture thereof. Also conteplated is a method for decreasing adsorption of glucose in a vertebrate, including mammal and bird, in the need thereof, AKG, AKG derivates or metabolites, AKG analogues or mixture thereof, for decreasing glucose adsorption as well as compositions for use in treatment.