Does L-theanine in tea really calm you down?
I see L-theanine cited everywhere as the reason tea is calming. Is it actually backed by research?
Yes, with caveats. L-theanine is a non-protein amino acid found almost exclusively in Camellia sinensis. EEG studies show it increases alpha-wave activity in the brain (the 'relaxed but alert' state) and partially blunts caffeine's adrenergic spike. A typical cup gives 10–25mg — therapeutic studies use 100–400mg, so a single cup is mild. Matcha and shade-grown teas (gyokuro, Anji bai cha) are highest. The 'mind clear but body calm' effect from a slow gongfu session is real and L-theanine-driven.
— Yurii — 931 Tea, 931 Tea