Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised,…
This kind of study measures how someone feels an hour after a dose during a lab stress task — does that tell us anything useful about whether it would help my day-to-day anxiety?
Suggestive but preliminary. Not settled. how we score evidence
Caveat on this rating: "The study was funded by a grant from Neurobrands CA, USA", a beverage company with a commercial interest in the L-theanine drink tested; the authors state the funder had no input into design, conduct, or interpretation. The tested product was a multi-ingredient drink, not isolated L-theanine, so the effects cannot be attributed to L-theanine alone.
L-theanine is sold in the US as a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA), and as a food additive it holds Generally Recognized as Safe (GRAS) status for use in beverages.
Thirty-four healthy adults aged 18-40 drank an L-theanine-based nutrient drink or placebo before a multitasking cognitive stressor. Self-reported stress one hour after dosing was lower on the active drink, and the salivary cortisol response was lower three hours after dosing; no cognitive performance changes were seen at all, and the brain-wave (alpha) changes appeared only in participants higher in trait anxiety and did not correlate with either the stress or cortisol results. This is a single-dose laboratory stress test in healthy volunteers, not a treatment study.
Worth asking
This kind of study measures how someone feels an hour after a dose during a lab stress task — does that tell us anything useful about whether it would help my day-to-day anxiety?
Source
Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. — White DJ, de Klerk S, Woods W, et al. (2016)
Indexed peer-reviewed journal
Read the source: https://doi.org/10.3390/nu8010053
DOI: 10.3390/nu8010053
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Industry funded
- Published in
- Indexed peer-reviewed journal
- Sample size
- 34
- Preregistered
- No
- Conflicts disclosed
- Yes
- Independent of proponent
- No
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Questions
How strong is the evidence behind this?
Resolv rates this source "early signal". Suggestive but preliminary. Not settled. It scores 44 out of 100 on our published rubric. One caveat travels with that badge: "The study was funded by a grant from Neurobrands CA, USA", a beverage company with a commercial interest in the L-theanine drink tested; the authors state the funder had no input into design, conduct, or interpretation. The tested product was a multi-ingredient drink, not isolated L-theanine, so the effects cannot be attributed to L-theanine alone. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. — White DJ, de Klerk S, Woods W, et al. (2016). Published in: Indexed peer-reviewed journal. DOI: 10.3390/nu8010053. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Industry funded. The researchers were not independent of whoever benefits from the result. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is l-theanine, theanine, suntheanine, alphawave, gamma-glutamylethylamide, green tea amino acid FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. L-theanine is sold in the US as a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA), and as a food additive it holds Generally Recognized as Safe (GRAS) status for use in beverages.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.