L-Theanine Capsules

L-theanine is an amino acid found naturally in the leaves of the tea plant, Camellia sinensis [1]. It’s what’s known as a non-protein amino acid, which means your body doesn’t use it to build proteins. It also adds to tea’s savoury, umami flavour [1]. Although L-theanine and caffeine are often mentioned together, they’re two different compounds that can both be found in tea [1].

A typical cup of green tea contains roughly 8 to 30mg of L-theanine [2]. A capsule gives you a measured 200mg, the amount used in the studies below. Each capsule contains L-theanine and a vegan capsule shell, that’s it. As with any food supplement, it shouldn’t replace a varied, balanced diet.

Why do people take L-theanine?
People tend to look at L-theanine for three everyday things: winding down, sleep and focus. Those are also the areas researchers have studied most in humans, so we’ve broken them down below.

Unwinding
In a 2019 study, 30 adults took 200mg of L-theanine a day for four weeks, and the researchers compared this with a placebo period. Scores on questionnaires about low mood, anxiety and sleep quality were lower after the L-theanine period, and so were scores for sleep latency and sleep disturbance. It’s a small trial, so it’s a starting point rather than the final word [2].

Sleep
A 2025 review pulled together 19 studies on L-theanine and sleep. Overall, people reported small improvements in how long it took to fall asleep, in daytime tiredness and in how well they felt they slept. However, 11 of the studies used L-theanine alongside other ingredients, so it’s hard to say what L-theanine did on its own [4].

Focus
A 2026 review of 31 randomised trials, with 1,168 participants in total, looked at attention. After a single 200mg dose, people did better on a choice reaction time test, which measures how quickly you respond when you have to pick between options. This was in short-term testing conditions, so it doesn’t tell us what happens with daily use [3].

Worth knowing

These studies didn’t test Naturecan’s capsules and can’t promise a particular result for you. L-theanine is a food supplement and shouldn’t replace a varied, balanced diet. 

Why choose Naturecan L theanine?

Many L-theanine capsules in IE are made from green tea extract, which means the capsule contains other plant compounds as well as L-theanine. Ours doesn’t. Each capsule contains 200mg of L-theanine and nothing else apart from the vegan HPMC capsule shell, so what you read on the label is what you get. 

That simplicity comes with choice. If you’d rather stock up, we also have 120 and 180 capsule options. Per day, that works out at about 33p for the 60-capsule pack, 29p for 120 capsules and 27p for 180 capsules.

Looking to buy l theanine IE? You can browse more in our brain health supplements range and compare it side by side with our other ingredients.

Ingredients: L-Theanine, Capsule Shell (Glazing Agent (Hydroxypropyl Methylcellulose)).

HPMC (hydroxypropyl methylcellulose) is the capsule-shell material. This product is suitable for vegans.

Take one capsule daily. Do not exceed the stated recommended daily use. This product should not be used as a substitute for a varied, balanced diet. Store in a cool, dry place out of direct sunlight. Keep out of reach of young children.