It is not exactly clear how theanine works. It might work for anxiety by increasing levels of gamma-aminobutyric acid (GABA), a brain chemical that is naturally calming. Theanine may also increase serotonin levels in the brain. It is thought that the supplement may also protect nerves in the brain from damage seen in Alzheimer's disease. In animals, it lowers norepinephrine levels, which may help lower blood pressure.
There is not yet enough scientific evidence to evaluate the effectiveness of theanine for any use (see Does L-Theanine Work? for more information).
A safe and effective theanine dose has not been established. Be sure to follow the specific instructions for your particular product.
(Click Theanine Dosage for more information.)
Theanine can interact with a few medications (see Drug Interactions With Theanine).
It is not known exactly what to expect from a theanine overdose. If you think you may have taken too much, seek immediate medical attention.
(Click L-Theanine Overdose for more information.)
Refer to the label of your individual theanine product for information on how to best store it. Keep this and all other medications or supplements out of the reach of children.