L-theanine is an amino acid found in green tea. Studies show that L-Theanine produces tranquilizing effects in the brain without drowsiness. It calms by helping to increase alpha-brain wave activity, the electrical brain activity commonly present when you are very relaxed. By diminishing feelings of stress, worry and anxiety, L-Theanine may help improve mental focus, learning and concentration. Single dosages of 200 mg of L-Theanine have been shown effective in studies. It is estimated that a person who drinks 6 to 8 cups of green tea a day may consume between 200 to 400 mg of L-Theanine. Natural Factors new L-Theanine provides this amino acid as a supplement, so you don't have to drink pots of green tea each day.