Abstract: The present invention is intended to provide compositions which exert excellent effects allowing improvement in the mental function of humans and animals other than humans, such as reduction of mental fatigue, maintenance and enhancement of concentration maintenance and enhancement of mental vigor, and the like. These compositions are provided as mentally functional compositions containing, as the active component, a mixture component comprising caffeine, theanine, and arginine which are contained in tea. It is preferable that caffeine, theanine, and arginine are mixed such that the mixing ratio approaches a ratio of 1:2:2. Further, by combining the above-described mixture component with sugar and citric acid, mentally functional foods and beverages can be also provided which are taken with ease and effective.

Abstract: Tea leaves are extracted in warm or hot water, and the obtained extract is contacted with a cation exchange resin ionically bonded to potassium ion. The potassium ion is ionically bonded to the cation exchange resin in advance. Divalent ions in the tea beverage are replaced with the potassium ions from the cation exchange resin. The electrical conductivity of the extract is controlled in this whole process. The natural flavor and quality of the tea are thereby maintained more certainly, since metal ions that cause muddiness or precipitation are effectively removed.

Abstract: The caffeine stimulation inhibitor that inhibits stimulation by combining the use of theanine extracted from tea leaves and/or a substance having theanine for its major active ingredient which is produced by extracting tea leaves with a solvent such as water, hot water or ethanol, chemical synthesis, microbial fermentation or plant tissue culturing. These active ingredients are able to inhibit the stimulatory action of caffeine without degrading the quality, such as the flavor and aroma, of caffeine-containing beverages and foods, allowing persons hypersensitive to caffeine to consume caffeine-containing beverages and foods without worry over its effects.