L-theanine is found in tea leaves and as a dietary supplement ingredient,and it can relieve fatigue, reduce blood pressure and improve learning and memory ability,but no hypnosis. An enzymatic method for manufacturing synthetic L-theanine (Suntheanine ) has been developed.
The regulatory status of theanine varies by country.
In Japan, L-theanine has been approved for use in all foods, including herb teas, soft drinks, desserts, etc. Restrictions apply to infant foods.
In the United States, the Food and Drug Administration (FDA) considers it to be generally recognized as safe (GRAS) and allows its sale as a dietary supplement. The German Federal Institute for Risk Assessment, an agency of their Federal Ministry of Food and Agriculture, objects to the addition of L-theanine to beverages.
The European Food Safety Authority EFSA advised negatively on health claims related to L-theanine and cognitive function, alleviation of psychological stress, maintenance of normal sleep, and reduction of menstrual discomfort.Therefore, health claims for L-theanine are prohibited in the European Union.