L-theanine (suntheanine) is an amino acid derivative that boosts your body's immune response. While it is naturally found in green tea, it can also be taken via pills. But don't hop on the L-theanine bus just yet. First, check out this video to find out if you need a pill-sized dosage of this dietary supplement and how it can be useful for pets.
As always, first consult with your doctor before making any major dietary changes.