Following a single dose of the L-theanine, subjects saw significantly greater increases in frontal region alpha power compared to placebo, which is considered reflective of relaxation.
A recent randomized, triple-blind, placebo-controlled crossover study1 found that supplementation with a patented L-theanine ingredient may help healthy adults manage stress. In the study, 15 subjects were given either 200 mg of AlphaWave L-theanine from Ethical Naturals Inc. (Novato, CA), or placebo during two study periods separated by a seven-day washout period.
Electroencephalogram (EEG), salivary cortisol, blood pressure (BP), heart rate (HR), and self-reported stress through State-Trait Anxiety Inventory (STAI) and visual analog scale (VAS) were used to assess subjects at baseline, then following a stress-inducing mental arithmetic test (MAT). Subjects were then given either the L-theanine or placebo. After 45-minutes, they completed the MAT and researchers collected EEG, BP, HR, salivary cortisol, STAI, and VAS measurements.
Results showed that the MAT increased HR, BP, and self-reported measures of stress and state anxiety. Following a single dose of the L-theanine, subjects saw significantly greater increases in frontal region alpha power compared to placebo after three hours, as measured by EEG. Brainwave alpha power is considered reflective of relaxation, with frontal region alpha waves observed during non-REM sleep and meditation. Subjects taking L-theanine also saw significant reductions in salivary cortisol one hour post-dose, and following the MAT.