L-Theanine, a tea amino acid sold as an inexpensive supplement for calm, focus and sleep, briefly, slightly sharpens attention within an hour of dosing. Effects on stress, sleep quality and low mood are small and inconsistent; people may feel they sleep better without sleeping longer. Side effects were mild and uncommon at tested doses. Most trials are small, short, often company-funded; any role in slowing aging rests on animal data. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Home blood pressure | No established target; change from own 1-week baseline | Safety check: additive lowering with blood-pressure drugs |
| PSQI sleep score | ≤5 | Expected to change: sleep quality |
| GAD-7 anxiety score | <5 | Expected to change: anxiety symptoms |
| Wearable total sleep time | No established target; change from own 2-week baseline | Safety check: shorter sleep seen in one trial |
Cadence: Home blood pressure three times weekly for the first 2 weeks; questionnaires at 4 weeks, then every 3 months; continuous wearable sleep tracking during the first 4 weeks