Caffeine

L-Theanine and Caffeine: What the Research Says (and Where It Runs Out)

19 Oct 2026 · Harry · 4 min read

Hour nine. The work's not done, and you need your head on the task, not only your eyes open.

That's what most people want when they go looking for L-theanine and caffeine. Here's what the research says about the pairing, and where it runs out.

The short answer

Caffeine helps you stay alert. In a 2025 trial on people kept awake all night, caffeine with 200mg L-theanine improved speed and accuracy on attention tests.

That trial used 160mg of caffeine and capsules, not a drink. It tells us about the pairing. It doesn't tell us about any one product, including ours.

What is L-theanine?

L-theanine is an amino acid that occurs naturally in tea leaves. It's also made as a supplement and added to some drinks.

It isn't a stimulant. Caffeine is. That's the whole reason the two get studied together: one gets you going, and researchers want to know what the other adds.

What does caffeine do on its own?

Caffeine helps you stay alert. Most of us already know that from the first coffee of the day.

It also hangs around. The Sleep Health Foundation says the effects of caffeine can last for several hours, often longer than you think. Healthdirect says healthy adults can have around 400mg a day. If you work odd hours, the timing matters as much as the amount, and we cover it in how long caffeine lasts.

What the 2025 trial did

The trial was published in the British Journal of Nutrition in 2025. Here's how it worked.

37 healthy adults, aged 22 to 30, were tested after a full night without sleep.
On separate occasions, each person took capsules of 200mg L-theanine plus 160mg caffeine, or a placebo. Neither the researchers nor the volunteers knew which.
About 50 minutes later, they did a computer-based attention task while sensors tracked their brain activity.

On the combination, people picked out targets more accurately. They also responded faster than they did on the placebo.

What the trial can't tell you

This is the part most articles skip, so here it is.

It was one night without sleep. The authors say the findings can't be directly extended to people who are short on sleep week after week.
The volunteers were young and there weren't many of them.
The task was a screen test. A worksite is messier.
It tested capsules, not a can.
It didn't report on jitters or side effects, so it says nothing about either.
TILT wasn't in the trial, and we don't claim it reproduces the result.

The wider research is small and mixed too. An older study found the pairing helped people switch between tasks, but it didn't change how alert they said they felt. Treat the pairing as promising, not proven for everyone.

What it means on a long shift

We built TILT around caffeine with L-theanine to help keep your attention on the task in the back half of the shift. That's the stretch where the work's not finished and neither are you.

The feeling we're after is locked in. Switched on, with a clear head. TILT is low sugar, so there's no sugar crash waiting for you at knock-off.

It tastes like a drink you'd pick anyway, too. If you want to see how it goes on your own roster, your first slab comes with a Bonus Mixed 8 Pack.

FAQ

Does L-theanine work with caffeine?

Some small trials say the pairing helps attention more than caffeine alone. In a 2025 trial on people kept awake all night, caffeine with 200mg L-theanine improved speed and accuracy on attention tests. The studies are small and not every one finds the same thing.

What is L-theanine found in?

It occurs naturally in tea leaves. It's also made as a supplement and added to some drinks.

How long does it take for caffeine and L-theanine to work?

The 2025 trial tested people about 50 minutes after they took the capsules. Everyone responds differently, and caffeine can stay with you for hours, so plan your last one around when you want to sleep.

Is there L-theanine in TILT?

Yes. TILT is built around caffeine with L-theanine. The exact amounts are printed on the can.

This article is general information, not medical advice. If you have a health condition or take medication, ask your GP or pharmacist about caffeine.

Built for the shift. See TILT.

For the label readers: 105.6mg of natural caffeine and 198mg of L-theanine in a 330ml can, 3.7g of sugar and 18 calories. Vegan and gluten-free. No artificial colours or preservatives. Every ingredient and milligram is printed on the can. Contains caffeine. Not recommended for children, pregnant or lactating women, or individuals sensitive to caffeine. Consume no more than 1 can per day.

Sources

CaffeineEnergy DrinkL-TheanineShift Work

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