L-Theanine
Amino acid from green tea that promotes calm alertness and deeper sleep.
What is L-Theanine?
L-theanine is an amino acid found almost exclusively in tea leaves (Camellia sinensis). It crosses the blood-brain barrier and promotes alpha brain wave activity, the state associated with relaxed focus. It is the compound responsible for why tea, despite containing caffeine, produces a calmer energy than coffee.
What does the evidence say?
A 2008 study by Nobre et al. in Asia Pacific Journal of Clinical Nutrition found theanine significantly increased alpha wave activity and reduced subjective stress response. A 2011 randomised controlled trial by Higashiyama et al. found 200mg L-theanine reduced cortisol responses and improved reaction time. Multiple studies confirm the synergistic effect with caffeine: theanine at 100–200mg blunts the jitteriness of caffeine while amplifying focus.
Good evidence from several studies, but with some limitations in size, duration, or methodology.
Dosage guide
| Effective dose | 100–200mg per day |
| Maximum dose | 600mg/day (studied without adverse effects) |
| Timing | 30 to 60 minutes before bed for sleep. With morning coffee for the caffeine stack. |
Best form to buy
L-theanine (the natural form). Suntheanine is a patented, pure L-isomer form used in many studies.
Who benefits most
Anyone who is anxious, stressed, or struggling with sleep onset. The caffeine stack is ideal for men who want mental clarity without stimulant-related anxiety.
Side effects and safety
Exceptionally well tolerated. No known significant adverse effects at normal doses.
“Cheap, reliable, and one of the few supplements where the effect is noticeable within days. The caffeine + theanine stack (1:2 ratio, e.g. 100mg caffeine with 200mg theanine) is the best nootropic stack available for the money.”