The Cognitive Benefits of L-Theanine

Green tea has been known for its health benefits for thousands of years.

Emperors in China used it to achieve long life; monks, to reach higher states of meditation; and students, to boost their study efforts.

The tea plant has many chemicals that contribute to these effects — but none as well-rounded as L-theanine.

The effects of L-theanine include:

• Protects the brain from the natural processes of aging
• Lowers anxiety symptoms
• Improves memory and concentration
• Boosts blood flow to the brain
• Supports deep, restorative sleep

Here, we’ll discuss the benefits of L-theanine, how it works, and what makes it so useful for cognitive function.

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What is L-Theanine?

A chemist would refer to l-theanine as an amino acid analog. This means it’s similar in chemical structure to an amino acid — the building blocks of proteins.

In its concentrated form, l-theanine induces a calm, focused mental state. This is useful for studying, preventing anxiety attacks, and supporting optimal cognitive health by preventing damaging states of hyperactivity and anxiety.

Its ability to calm the mind also makes it desirable for public speakers and people who have a hard time falling asleep due to racing thoughts before bed.

L-Theanine Only Comes From High-Grade Tea

L-theanine is manufactured in the leaves of the tea plant (Camellia sinensis).

It’s responsible for many of the cognitive enhancing effects of tea and contributes to tea’s desired umami flavour. Only very high-grade teas (such as gyokuro or matcha) retain this compound in high enough amounts for effective doses.

The reason behind this is that while tea plants are growing, they naturally produce high levels of this compound — but as the scorching hot sun beams down on the leaves during the day, the L-theanine breaks down. By the time the leaves are harvested, there’s almost no L-theanine left.

To keep L-theanine content high — and improve the tea’s flavour and cognitive benefits — farmers will use special shade cloths for the final 2-6 weeks before harvesting the plants for tea.

This is extremely labour-intensive but ensures the L-theanine content is in the highest amount possible. The flavour and relaxation effects of these high-grade green teas are what make them valuable and highly sought-after

Making L-Theanine

Manufacturing L-theanine is done by extracting the compound from the leaves and concentrating it. High-quality shade-grown green tea will have about 1-2% L-theanine content by dry leaf weight. ¹

The combination of relatively high concentrations of the compound and the low recommended dose of L-theanine (200–700mg) make this natural cognitive enhancement supplement reasonably priced compared to other nootropic plant extracts.

Most L-theanine is sourced from the plant directly, while some brands use synthetic L-theanine manufactured in a lab.

Some versions of L-theanine such as Suntheanine® use what we call enantiopure L-theanine. It goes through a secondary process to make all L-theanine the same isomer.

An isomer is a term used to describe the chemical variability within the same molecule. It’s like your right and left hand — they’re both hands and do the same things, but are mirror images of each other. The same happens in chemistry — almost all chemicals have both a right-handed and left-handed version.

Suntheanine® and similar enantiopure L-theanine are considered slightly stronger than regular L-theanine.

How L-Theanine Works

L-theanine offers three main mechanisms for its effect profile:

1. It increases dopamine levels in the brain
2. It inhibits glutamate — the primary stimulating neurotransmitter
3. It improves blood flow to the brain

All of these effects compound together to produce its anti-anxiety, neuroprotective, memory boosting, and cognitive enhancing effects.

Inducing Alpha Brain Waves

The primary benefit of L-theanine is its ability to induce what we call alpha waves. ²

Brain waves are measured using a special device called an electroencephalogram (EEG for short). Researchers use EEG machines to measure the electrical activity of the brain to determine the patient’s mental status.

Alpha waves are considered an index for mental relaxation. When our brains are in alpha-wave states, we feel a calm, clear-headed focus — the ideal mental state for studying, learning, and making wise decisions under pressure.

Mental States According to EEG Metrics Include:

1. Alpha-waves (7.5–12.5 Hertz) → Calm, focused, relaxed
2. Beta waves (12.5–30 Hertz) → Alert, attentive, anxious
3. Delta waves (0.5–4  Hertz) → Deep sleep
4. Theta waves (7–8 Hertz) → Sleep and meditation

Researchers are still disputing the intricate mechanisms L-theanine uses to induce alpha-wave states. However, this effect is likely the byproduct of L-theanine’s ability to control other neurotransmitters in the brain such as dopamine, GABA, and glutamate.

L-Theanine and Dopamine

We use dopamine for a wide range of functions in the brain. It helps control our hormones, it regulates our habits and instincts and is heavily involved in our ability to focus and stay motivated.

People suffering from attention deficit disorders (ADD and ADHD) are often found to have low levels of dopamine in the brain. ³ The most common treatment for these conditions are drugs such as Adderall and Ritalin.

They work by boosting dopamine levels indirectly by preventing the neurons from breaking it down after it’s released.

L-theanine offers similar effects on increasing dopamine levels — though to a lower intensity. ⁴

Suntheanine®, a preparation of L-theanine, was shown to provide a dose-dependent increase in dopamine levels in rats. ² This means that the more L-theanine consumed, the higher the dopamine levels were.

L-Theanine and Glutamate

The amino acid L-theanine is similar in structure to our primary neurotransmitter, glutamate. Roughly 90% of the neurological activity in the brain involves glutamate. ⁴

Glutamate is the primary stimulatory neurotransmitter — meaning that it’s used to activate the neurons, telling them to fire an electrical impulse down their axon to transmit messages to other areas of the brain and body.

When we’re in a state of hyperactivity or going through what we would refer to as anxiety, glutamate is firing out of control. There is too much electrical activity in the brain to be able to think clearly and focus intently.

L-theanine changes this through its similar structure to glutamate.

It works by binding to the glutamate receptors — without activating them. This prevents the real glutamate from activating the receptor instead. ⁵ We call this competitive inhibition because it competes with the real glutamate to inhibits its effects.

One study observed that L-theanine could lower the intensity of perceived stress by inhibiting the effects of glutamate. ⁵

L-Theanine and Cerebral Blood Flow

One of the most important benefits of L-theanine is its ability to improve blood flow to the brain.

Poor blood flow is associated with conditions such as Alzheimer’s disease and dementia. ⁶

If blood flow is impaired, it becomes difficult to remove harmful byproducts and debris from around the neurons — which can build up and lead to neurological damage over time.

One study investigated the effects of L-theanine on caffeine-induced cerebral blood flow restriction. The study found that small doses of L-theanine in the form of green tea were able to eliminate the constriction of blood flow induced by high doses of caffeine. ⁷

This explains L-theanine’s beneficial effects on Alzheimer’s disease. ⁸

L-Theanine Dosing

The dose of L-theanine doesn’t need to be very high to be effective. The effects can be felt with just a few cups of high-grade, shade-grown green tea — even though the actual dose of L-theanine in this form is low.

Higher doses produce stronger effects, which can only be reached using supplementation of L-theanine.

The normal dosage range of L-Theanine is 200–700 mg per day. Usually, this dose is split into two or three separate doses throughout the day.

Summary of L-Theanine

L-theanine is an incredibly useful compound found in the tea plant. It’s an amino acid that mimics the shape of one of our most common neurotransmitters, glutamate.

Supplementing L-theanine is useful for inducing a calm, clear-headed mental state — which makes it useful for studying, working under pressure, offsetting anxiety and stress, and improving our ability to fall asleep at night.

There is a wealth of research on this useful compound and likely to be much more in the coming years. Who knows what other benefits we’ll find this compound has to offer?

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Originally posted on January 9, 2019, last updated on March 11, 2023.

References

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7. Dodd, F. L., Kennedy, D. O., Riby, L. M., & Haskell-Ramsay, C. F. (2015). A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. Psychopharmacology, 232(14), 2563-2576.[↩]
8. Kim, T. I., Lee, Y. K., Park, S. G., Choi, I. S., Ban, J. O., Park, H. K., … & Hong, J. T. (2009). l-Theanine, an amino acid in green tea, attenuates β-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-κB pathways. Free Radical Biology and Medicine, 47(11), 1601-1610.[↩]