L-Theanine
L-theanine is an amino acid found in tea leaves that is not used to build proteins. Black and green tea contain it alongside caffeine.
Also listed as Theanine
What do short trials tell us about safety?
The four-week adult trial reported no apparent adverse events, but it excluded pregnant women and people with severe physical illness. That is reassuring for its small study population, not evidence of safety during pregnancy, serious illness or years of use. 1
Study doses are not a safety ceiling
In its assessment updated in 2003, Germany’s BfR could not determine a safe daily amount of isolated theanine and highlighted unresolved interactions with alcohol and medicines. This is a historical assessment of fortified drinks, not a statement that the agency has reviewed all later trials. The studied 200–400 mg range should not be read as an official upper limit. 2 3
For information, not individual medical advice. Ingredient studies do not establish the effectiveness of these products.