L-Theanine is widely used in dietary supplements and functional foods for its calming and cognitive-enhancing effects. It promotes relaxation without drowsiness by increasing alpha brain wave activity, which is associated with a state of wakeful relaxation. It is commonly included in nootropic formulations to support focus, attention, and mental clarity, especially when combined with caffeine. L-Theanine also helps reduce stress and anxiety by modulating neurotransmitters such as GABA, serotonin, and dopamine. It is used in products targeting sleep quality, mood balance, and overall mental well-being. Additionally, it has been studied for potential benefits in improving cardiovascular health and immune function.