★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.
How much theanine a tea holds depends on its type, region and season
Across 2,983 Chinese teas, lightly fermented kinds such as green tea sat among the richest in theanine, and spring-picked leaf held the most. That is the leaf itself, not a brewed cup.
What the study found
Spring-picked leaf held the most theanine across 2,983 Chinese teas
How much theanine a leaf carries is not fixed. Across 2,983 Chinese tea samples in seven categories, the lightly fermented teas, green tea among them, sat among the richest in theanine and the other savoury amino acids, and the amount moved with tea type, growing region and harvest season.
The caveat · The leaf, not a brewed cup
This measured the tea itself, not a brewed cup, so what reaches a drink is a separate question. It is a chemistry survey, so it says nothing about what any of it does in a person.