CanPrev L-Theanine with Magnesium - Promotes a state of relaxation so that you can stay focused and productive. L-theanine is a non-protein amino acid found in green and black tea and is especially beneficial for anxiety sufferers because it increases dopamine and GABA receptors in the brain. GABA is a chemical receptor that reduces the activity of neurons that it binds to. In other words, it helps slow down the feelings of fear and stress when neurons become over excited.