The study and its comparison
Forty-eight healthy adults received caffeine, theanine, both, or neither. The doses were 250 milligrams of caffeine and 200 milligrams of theanine; testing began around 40 minutes later. [1]
Caffeine increased alertness, jitteriness and blood pressure. Theanine opposed the pressure rise, but did not significantly change jitteriness or alertness. It also slowed overall reaction time on the visual-probe task. [1]
What the finding establishes
This single-session result does not establish that adding theanine makes any caffeinated product safe or improves every form of attention. The fixed doses and task should remain attached to the claim. Funding and conflicts were not established from the retrieved abstract. Subjective calm and cardiovascular measurements are separate outcomes. [1]
A hypothetical distinction
Imagine someone still feels jittery despite a smaller pressure response. The two findings can coexist without contradiction.
| Detail | Interpretation |
|---|---|
| Measured outcome | Keep the endpoint specific |
| Study preparation | Not every retail product |
| Remaining uncertainty | Not resolved by a mechanism |
Sources for this article
- Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together - PubMed
Source consulted: 2026-09-19. This is a reference resource, not a claim that we conducted the studies or tested a product.