L-theanine HCL is an amino acid found in tea leaves, such as black and green teas. It can also be produced synthetically or can be used as an ingredient in a L-theanine supplement. 

L-theanine may help support a number of health benefits, including stress levels and cognitive function (study) and immunity for specific populations (study).* 

L-theanine and sleep

L-theanine may also help to support sleep quality and duration when mixed with GABA (study). Research also found that L-theanine could help support heart health and positively influence the Tension-Anxiety score for specific people (study).*

L-theanine and stress-relief

Individuals with high levels of anxiety often have high levels of tension. In order to measure the level of stress in a person, a tension-anxiety score can be calculated. This score is obtained by subtracting the anxiety score from the tension score. The higher the tension-anxiety score, the more tension a person is experiencing.*

When it comes to stress relief, L-theanine works by reducing the body's production of cortisol, the stress hormone. In one study, participants who took L-theanine HCL per day experienced lower levels of stress than those who did not take the supplement (study).*

L-theanine and cognition

Certain types of adults who used L-theanine during research showed improvements in attention span (study).* This is one the reasons why sometimes L-theanine is referred as nootropic. A nootropic is a type of supplement that is thought to support cognitive function.*

In addition to its stress-relieving and cognitive-enhancing effects, L-theanine may also offer other health benefits. For example, L-theanine HCL has been shown to help support immunity by increasing the production of antibodies and white blood cells of athletes after strenuous physical exercise (study). 

As always, talk to your doctor before taking any supplements or vitamins such as as a liposomal vitamin C. Get professional advice if you think you might need an L-theanine supplement or are already taking one to ensure you're not exceeding the amounts you may need.