It Reduces Anxiety
In addition to moderate doses of caffeine (compared to coffee), green tea has a compound called L-theanine, an amino acid that can cross the blood-brain barrier and enter the brain. L-theanine contains a compound known as GABA, which is a neurotransmitter that increases the production of dopamine, stimulates soothing alpha brain waves, and reduces anxiety.
Caffeine and GABA work together to produce an even greater effect than just one or the other consumed alone. The result of this combination is a caffeine boost that doesn’t give you jitters and can make you feel calm (instead of more anxious, as caffeine alone can do) and more stimulated. The result is an effect on alertness greater than that of coffee.