Theanine is a key amino acid that has a calming effect on cognitive function. It crosses the blood-brain barrier and helps create a state of relaxation while maintaining alertness. When exposed to the brain, it stimulates the production of gamma-aminobutyric acid (GABA), a chemical produced by the brain that blocks excitatory stimuli that cause stress. Theanine is an amino acid found in green tea that can cross the blood-brain barrier and increase brain wave frequency. This helps relieve anxiety and promotes mental clarity and focus. Studies show it may also protect the nervous system from the effects of stress, which can cause dangerous blood pressure spikes and carb cravings, which can lead to stubborn belly fat accumulation.