Disclosed is a method for enhancing physiological action of caffeine in an oral composition for mental fatigue-reducing action, drowsiness-preventing action, or concentration-maintaining action which contains caffeine as an active ingredient, wherein caffeine is combined with ornithine or a salt thereof in said oral composition, in an amount equivalent to 0.1 to 100 parts by weight of free ornithine based on 1 part by weight of caffeine. Also disclosed is the use of such a composition for reducing mental fatigue, drowsiness and maintaining concentration.
