Amino acid
L-Theanine
γ-glutamylethylamide
The amino acid that makes green tea calming rather than jittery. L-theanine promotes a state of relaxed alertness without sedation — useful for stress and focus alike.
Our pick, and why
Choosing a l-theanine on iHerb
Doctor's Best is our pick: it's the only one here that explicitly names Suntheanine® on the label — the branded form with its own published trial record — at 150 mg, within the studied range. NOW Foods delivers 200 mg and is a highly reputable manufacturer, but neither the label nor the iHerb listing names the source of its L-theanine, so we cannot confirm it matches the trialed form. Jarrow is in the same position. Both are likely fine in practice, but on a site that takes evidence transparency seriously we can only highlight the one that states its pedigree. Honest caveat: if dose matters more to you than brand pedigree, 200 mg from NOW or Jarrow is a reasonable, lower-cost choice.
How we judge these
Suntheanine® branded form stated on label, dose 100–200 mg, no unstated caffeine.
| Product | Product | Branded form | Dose / serving | Added caffeine | Other actives | Meets it | Link |
|---|---|---|---|---|---|---|---|
| Our pick Doctor's Best L-Theanine with Suntheanine® | Suntheanine® | 150 mg | No | None | ✓ | iHerb → | |
| NOW Foods L-Theanine 200 mg | Not stated | 200 mg | No | Inositol 100 mg | ✓ | iHerb → | |
| Jarrow Formulas Theanine 200 | Not stated | 200 mg | No | None | ✓ | iHerb → |
- Doctor's Best L-Theanine with Suntheanine®Our pick
- Branded form
- Suntheanine®
- Dose / serving
- 150 mg
- Added caffeine
- No
- Other actives
- None
- Meets our criterion
- ✓
- NOW Foods L-Theanine 200 mg
- Branded form
- Not stated
- Dose / serving
- 200 mg
- Added caffeine
- No
- Other actives
- Inositol 100 mg
- Meets our criterion
- ✓
- Jarrow Formulas Theanine 200
- Branded form
- Not stated
- Dose / serving
- 200 mg
- Added caffeine
- No
- Other actives
- None
- Meets our criterion
- ✓
Specs verified against live listings at time of writing and can change — confirm on the product page. Links are affiliate links; details.
L-theanine is the reason a cup of green tea feels calmer than a cup of coffee, despite both containing caffeine. It increases alpha-wave activity — the brain rhythm associated with relaxed, wakeful states — and unlike most calming compounds it does this without making you sleepy.
That “relaxed but alert” quality makes it one of the few stress-support ingredients that’s equally at home before a stressful meeting and before bed.
What to look for
- Plain L-theanine (Suntheanine is a well-known branded form)
- 100–200 mg per serving
- Optional caffeine + theanine combos if focus is your main goal