Does l-theanine work?

Overall Effectiveness Rating for L-Theanine

The overall effectiveness rating for l-theanine is 2 out of 3. This rating means there is some evidence that using l-theanine may lead to positive results. This rating also means that some evidence does not back up all claims. Below you can find individual ratings for specific claims.

Overall Confidence Rating for L-Theanine

There are 4 studies in the database on l-theanine; the confidence rating is 20. A score above 80 means the effectiveness rating for this supplement is reliable. A score under 80 means there is insufficient evidence to ensure a reliable effectiveness rating. Note, this rating is for l-theanine as a whole. There are also individual ratings for the claims below.

Products Containing L-Theanine

Products Containing L-Theanine
Nano Shred Max
1UP For Men
Physique Series Fat Burner
Pre-Train V2
Full list of all 104 products containing L-Theanine.

Individual Claims

The overall ratings above do no necessarily reflect each claim about l-theanine. Individual claims can have higher or lower ratings. For example, some supplements may have a lot of backing for one claim, but be completely useless for another. Click on claims below for more information.

Immune Health Claims Effectiveness Rating Confidence Rating
improve immune function
reduce frequency of the common cold

Mental Health Claims Effectiveness Rating Confidence Rating
improve cognitive ability

General Health Claims Effectiveness Rating Confidence Rating
improve sleep quality


Title of Study
Effects of L-Cystine and L-Theanine Supplementation on the Common Cold: A Randomized, Double-Blind, and Placebo-Controlled Trial
Effects of oral supplementation with cystine and theanine on the immune function of athletes in endurance exercise: randomized, double-blind, placebo-controlled trial
Improving mental regeneration after physical exercise
The effects of L-theanine (SuntheanineĀ®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial