Short answer: a rushed cup of green tea has about 8 mg of L-theanine. A well-brewed cup of quality leaf has about 20 mg. The studies that showed a calm-focus effect used about 100 mg, with a little caffeine. How you brew - and what you brew - decides where you land.
What is L-theanine?
An amino acid found almost only in tea (say it "el-THEE-uh-neen"). It's linked to relaxed-alert brain activity - awake and calm at the same time.
On its own its effects are small. Paired with caffeine, it improves attention: switching cleanly between tasks and staying accurate.
How much is in your cup?
| What you drink | L-theanine | Caffeine |
|---|---|---|
| A rushed cup (200 ml, 2-minute steep) | ~8 mg | ~25–40 mg |
| A well-brewed cup of quality leaf, e.g. Jade Mountain (3 g, 200 ml, 80°C, 3 min) | ~20 mg (up to ~30+ for the best leaf) | ~50 mg |
| Second steep of the same leaves | about half the first | most of the first |
| Matcha and shade-grown teas (gyokuro) | Higher - varies widely by product | Higher |
| Green Goddess gem (lab-tested) | 102 mg | ~5 mg |
| Dose used in the attention studies | ~100 mg | 40–50 mg |
Well-brewed figures are estimates scaled from lab analysis of quality green teas (6.6 mg theanine and 16.3 mg caffeine per gram of leaf on average, best teas near 11 mg theanine per gram). Jade Mountain itself hasn't been lab-tested yet. Green Goddess includes added L-theanine on top of the tea.
What changes the number
- Steep time - the biggest lever. A quick dunk leaves a lot of it in the leaf. Give loose leaf 3–4 minutes.
- Enough leaf. About 3 g (a heaped teaspoon) per 200 ml. Less leaf, less theanine.
- The leaf itself. Young buds (like Jade Mountain) and shade-grown teas (gyokuro, matcha) are known for more. Shading keeps more theanine in the leaf, because sunlight drives the plant to turn it into catechins.
- Temperature is for taste. Heat doesn't destroy L-theanine. We brew at 75–80°C because boiling water makes green tea bitter - a slightly longer steep makes up for the cooler water.
- Re-steep. The second steep gives about half the theanine again, most of the caffeine and almost all the EGCG. Same leaves, more value.
- Freshness. Store leaf airtight, dark and cool. Old, stale tea brews flat.
How much do you actually need?
For the calm-focus, attention effect, the human trials used about 100 mg L-theanine with 40–50 mg caffeine. That's more theanine than a standard cup of tea alone usually gives you.
A quality loose leaf, well-brewed cup gets you bigger, steady lift. To reach the trial range: one Green Goddess gem plus a well-brewed cup ≈ 120 mg theanine + 55 mg caffeine - comparable to the dose used in the studies.
For calm on a stressful day, studies used around 200 mg L-theanine - two gems is about that, with only ~10 mg caffeine.
Does theanine cancel caffeine's jitters?
Not really. In a high-dose trial, theanine softened caffeine's rise in blood pressure but didn't significantly change how jittery people felt. Green tea feels smoother mainly because of the dose - about a third to half the caffeine of a filter coffee. What theanine adds is the sharp part: accuracy, focus, less distraction.
Calm comes from the dose. The edge comes from the pairing.
Keep it in proportion: the studies are small and mostly used supplements rather than tea. The effect is on mental performance more than how energetic you feel, it lasts hours, and it doesn't replace sleep.
📚 Keenan et al., 2011 (theanine per cup, Food Chemistry); Boros et al., 2016 (theanine and caffeine in quality green teas, Pharmacognosy Magazine); Zimmermann & Drees, 2025 (second infusions, Heliyon); Owen et al., 2008; Giesbrecht et al., 2010; Einöther et al., 2010; Rogers et al., 2008; Camfield et al., 2014.