The Verge - After a long day, we all want to slow our heart rate and breathing, loosen our muscles, and lower our blood pressure. We want to calm the mind and body, decreasing tension. We want to interrupt our stress hormonal cascade, ultimately reducing our own hostility. We want to kick back and activate our parasympathetic nervous system. You know, relax.
Some small studies found that l-theanine may reduce stress, induce relaxation, and make it easier for people to get to sleep. Chanaka Kahathuduwa, an assistant professor at Texas Tech University, is responsible for several studies on the amino acid, both alone and combined with caffeine. Kahathuduwa found that l-theanine had an effect, though it appeared to be subtle. “I don't think it's equivalent to the current medications in use,” he tells me.