L-Theanine

L-theanine is an amino acid found almost exclusively in tea. It's non-proteinogenic, meaning your body doesn't use it to build proteins — it's used and cleared, not incorporated.

It's the reason a cup of green tea feels different from a cup of coffee containing the same caffeine.

Less to untangle here than with magnesium. L-theanine is sold as itself: 200 mg on a label means 200 mg of L-theanine, with no compound-weight arithmetic to do.

What's worth checking is purity. We hold our supplier to a minimum of 98%, and identity and potency are verified for each lot.

This is the distinction that matters most, and the reason L-theanine is in this formula instead of melatonin.

Melatonin is a hormone. It carries a timing signal to your body clock, which is why it's genuinely useful for jet lag and shift work.

L-theanine isn't a hormone and doesn't act on the body clock. It doesn't knock you out; it lowers the volume.*

Sleep. Two systematic reviews published in 2025 give us something better than single trials to point at.

The first searched five databases plus the Cochrane trials register through September 2024 and pooled 19 randomized controlled trials covering 897 participants. L-theanine produced statistically significant improvements in three outcomes: subjective time taken to fall asleep (SMD 0.15, 95% CI 0.01–0.29, p = 0.04, across 10 studies), subjective daytime dysfunction (SMD 0.33, 95% CI 0.16–0.49, p < 0.001, across 9 studies), and overall subjective sleep quality (SMD 0.43, 95% CI 0.04–0.83, p = 0.03, across 12 studies).

The second reviewed 13 trials in 550 participants, restricted to L-theanine given on its own at 50–900 mg per day. Its authors concluded that supplementation in the range of 200–450 mg per day appears to be a safe and effective way to support healthy sleep in adults — their words, and a conclusion about the ingredient, not about any product.

Stress response. A double-blind placebo-controlled crossover trial in 34 healthy adults put participants through a demanding multitasking task. Subjective stress response was significantly reduced an hour after dosing compared with placebo, and the salivary cortisol response to the stressor was lower three hours after dosing. Worth knowing when reading it: the trial tested an L-theanine-based nutrient drink, not L-theanine on its own in a capsule.

That it makes you sleep longer. There is little evidence L-theanine increases total sleep time. It appears to change how the night feels, not how long it lasts.

That the effects are large. Both 2025 reviews describe effect sizes in the small-to-medium range.

That the outcomes are objective. The improvements are largely self-reported — how people rated their sleep and their next day. Reviewers in both papers called for larger trials using objective measures such as polysomnography.

That it sharpens your thinking. The 34-person stress trial observed no treatment-related change in cognitive performance — an absence of effect, which is reassuring for something taken at night but is not a benefit. A 2025 meta-analysis of L-theanine and cognition reached a conclusion its own title describes as promising but not conclusive. We make no cognitive claim.

Human trials span roughly 50–900 mg per day. The range identified in the 2025 review as effective for supporting healthy sleep in adults is 200–450 mg per day.

TAO Daily — Sleep & Calm provides 200 mg per two-capsule serving — the floor of that range.

Commonly taken in the evening, 30–60 minutes before bed, with or without food.

If you're pregnant, nursing, or taking medication, talk to your healthcare provider before use.

Because it does a specific job that melatonin doesn't: supporting a calmer state before sleep without acting as a sedative or shifting your body clock.* Because the evidence for that job, while modest, is real, recent, and pooled across nineteen randomized trials rather than resting on one study. And because 200 mg sits at the lower end of the 200–450 mg/day range identified in that review — a nightly dose rather than a loading dose, which is the right shape for a product you take every day.