L-Theanine: verification pending

References

1. Owen et al., randomized double-blind crossover (n=27 healthy volunteers): L-theanine + caffeine in combination improved speed and accuracy on attention-switching tasks and reduced distractibility vs caffeine alone — supporting the theanine + caffeine attention claim. PubMed
2. Haskell et al., randomized double-blind crossover: the L-theanine + caffeine combination produced superior cognitive benefits vs either alone, with improved visual processing accuracy, faster reaction times, and reduced mental fatigue. PubMed
3. Foxe et al., randomized crossover (n=27): caffeine 50 mg + L-theanine 100 mg significantly reduced error rates on the Sustained Attention to Response Task vs placebo — supporting the sustained-attention claim. PubMed
4. In a small (n=12) crossover trial, L-theanine taken before a mental arithmetic stressor attenuated heart-rate and salivary IgA responses versus placebo, which the authors attributed to reduced sympathetic nervous system activation. PubMed
5. This review of human EEG studies reports that L-theanine significantly increases alpha-frequency brain activity, indicating it relaxes the mind without inducing drowsiness, at doses above those typically found in a cup of tea. PubMed
6. A randomized, double-blind, placebo-controlled crossover trial reported that an L-theanine-based drink was associated with a reduced subjective stress response to a cognitive stressor, supporting L-theanine's role in normal relaxation response. PubMed
7. Plasma L-theanine concentrations rose in proportion to the oral L-theanine dose administered (200-600mg) in healthy human subjects. PubMed
8. In healthy adults, orally administered L-theanine is rapidly absorbed with plasma Cmax reached near 0.8h and dose-proportional AUC across 50-200mg. PubMed