Theanine, a naturally occurring amino acid in green tea, crosses the blood brain barrier and helps to produce a calming effect, inducing a feeling of relaxation and well-being. An increase in alpha waves has been documented, and the effect has been compared to getting a massage or taking a hot bath. Theanine does not cause drowsiness or interfere with the ability to think. Animal studies have shown that theanine actually enhances the ability to learn and remember possibly by reducing the tendency to worry. Theanine neutralizes the action of caffeine somewhat. The effects can readily be seen in EEGs of rodents given caffeine, then theanine. This is why tea does not have the same stimulating effect of the same amount of caffeine. Theanine increases GABA, while caffeine decreases it. GABA not only relaxes, it also creates a sense of well-being. Theanine also increases levels of dopamine, another brain chemical with mood-enhancing effects.

The safety of L-Theanine has been well established, as it occurs naturally in tea which has been consumed for centuries, and has been approved in Japan for addition to any food, except baby food. It takes effect within 30 minutes after consumption and has no known cautions or drug interactions.

Based on the results of clinical studies, it has been established that L-theanine is effective in single dosages in the range of 50-200mg. It is suggested that subjects with higher levels of anxiety take a dose at the higher end of the effective range (100-200 mg) for best results. It is estimated that a heavy tea drinker (6-8 cups daily) will consume between 200 to 400 mg of L-theanine daily. 100 to 200 mg 1 to 3 times daily is suggested as needed depending on stress and anxiety levels. L-theanine can be taken in capsule form or added to any liquid where it readily and completely dissolves.