Theanine is an amino acid found in tea and is thought to increase feelings of calm by interacting with alpha brain waves. Alpha brain waves are brain waves that are associated with relaxation. Huberman has mentioned many times that he uses Momentous L-Theanine.

Theanine is believed to relax the mind without causing drowsiness by significantly increased activity in the alpha frequency band. Data indicates that its use as a dietary supplement can dramatically affect mental alertness. Beyond that, increased alpha activity plays a vital role in focusing correctly.

In a small number of cases, theanine is problematic for those with night terrors or that sleepwalk in that it increases the intensity of dreams. It has also been found to have the opposite effect in that it can be too stimulating for about 10% of people that try it and can keep them awake.