L-Theanine is an amino acid that is not commonly obtained through dietary sources. It is structurally similar to the neurotransmitters Gaba and glutamate, and acts in a similar manner in the brain following oral ingestion.l-Theanine has been found to support feelings of relaxation without causing sedation. It also supports healthy stress levels and attention span. These properties make it ideal for combining with caffeine as a way to attenuate the jitteriness some people experience from it. The combination of L-Theanine and Caffeine, for example, has been shown to support cognitive functions such as memory, focus, energy, and problem-solving ability.