Does L-Theanine Lower Cortisol? (What the Research Shows)

L-Theanine: One of the Most Underrated Supplements for Cortisol

We've seen L-Theanine do wonders for clients suffering from stress symptoms. One study in particular has stood out in this area and proves the supplement's effectiveness.

The Study Design

This study was published in 2016 in the journal Nutrients. People were given either a drink containing:

• ➠ L-theanine (200 mg)
• ➠ L-alpha glycerylphosphorylcholine (alpha GPC; 25 mg)
• ➠ Phosphatidylserine (1 mg)
• ➠ Micronized chamomile (10 mg)

Or a placebo, alongside a cognitive assessment designed to induce stress.

While the drink did contain these other ingredients, they are far below (1–10%) their typical dosing — so their impacts were likely small or negligible.

Study Results

People consuming the L-Theanine drink reported markedly lower stress within the first hour. They actually felt less stressed with the L-theanine than they did prior — even while taking the assessment.

L-Theanine also completely prevented the rise in cortisol from the assessment.

While those without L-theanine showed markedly higher cortisol 3 hours after the test, those with L-theanine had lower cortisol — lower than before the stress test even began.

That's powerful.

Why is Theanine so Good for Stress?

L-Theanine is structurally similar to the amino acid glutamate — the primary excitatory neurotransmitter in the brain. In excess, glutamate can contribute to stress, OCD, ADHD, anxiety, and even depression.

Excess glutamate will make you feel wired and scatterbrained.

We do need some glutamate though — it helps with brain cell growth, stimulates dopamine production, and is necessary for clarity and alertness.

Theanine acts primarily by inhibiting the release of glutamate from neurons, producing a calming effect. It can also stimulate some glutamate receptors, reaping the dopamine and neurogenesis benefits while keeping us calm.

Additionally, theanine boosts GABA — our primary inhibitory neurotransmitter. GABA is the opposite of glutamate: it chills you out, promotes deep sleep, and crushes anxiety.

Theanine can also raise glycine levels in the brain — another neurotransmitter involved in inhibition, relaxation, and the formation of new brain cells.

Theanine also has antioxidant and anti-inflammatory effects.

It makes sense why theanine is so effective and safe for so many different things — it really can help to balance things out in the brain, without acting non-discriminately like a drug.

How Much L-Theanine Should I Take to Lower Cortisol?

Typical doses are from 200–400 mg.

Controlling your stress and cortisol is critical for your overall health. If you don't get that under control, it'll be difficult to solve any other health goal.

Theanine can be a part of a more comprehensive plan to keep your cortisol in check. You can find our recommended source here.

How Long Does It Take for L-Theanine to Lower Cortisol?

The study used a single 200 mg dose taken before the stressor. Stress relief was reported within the first hour, with cortisol reduction measurable at 3 hours post-dose.

When Should I Take L-Theanine for Anxiety?

Based on this, taking L-theanine 30–60 minutes before a stressful event appears to be the most effective timing.

Analyze & Optimize Team