L-Theanine Benefits on Cognitive Function & Health

Table of Contents

Green tea has been in use in Chinese medicine for over three millennia. It’s used with other herbs or concentrated liquid to improve energy and concentration.

L-theanine is a compound that naturally occurs in tea leaves. The amount found in tea leaves varies depending on where and how it is grown, produced, and harvested.

Caffeine, the other component of tea, raises dopamine levels in the brain, improves attention, cognition, and mood. It also makes one of the most popular nootropic combinations: Caffeine and L-Theanine.

L-theanine uses treat various medical and mental health issues. With a popularity growing rapidly across the world.

Caffeine’s benefits on cognitive function occur faster than l-theanine’s due to its faster absorption and bio-availability, reaching peak plasma levels in as little as 30 minutes.

L-theanine improves cognitive performance, reduces stress response, and even protects against common cold. Regularly consuming l-theanine protects against oxidative damage (also known as “free radicals”).

In addition, it increases glutathione concentration in the liver by promoting the ability of liver enzymes to clear toxins from the blood.

Research further suggests l-theanine promotes longevity and has anti-aging properties.

L-Theanine and Neuropsychiatric Disorders

L-theanine improves learning, memory, and cognitive function. Studies show that drinking green tea lowers the likelihood of cognitive degeneration, improves mood, and boosts our ability to cope with stress

L-theanine may also remedy symptoms of ADHD, OCD, panic, bipolar, and mood disorders. 

In a randomized placebo-controlled study on the effects of L-theanine alone vs. in combination with caffeine on mood and cognitive performance suggest a combined treatment improves cognitive function. [reference]

Caffeine enhances performance on mental tasks while also increasing alertness and vitality.

Long-term l-theanine use (3 to 4 weeks) provides neuroprotective benefits by increasing brain-derived neurotrophic factors (BDNF).

Science Direct, a database of peer-reviewed scientific research, define neuroprotection as:

the ability for a therapy to prevent neuronal cell death by intervening in and inhibiting the pathogenetic cascade that results in cell dysfunction and eventual death.” 

L-Theanine on Anxiety and Stress

L-theanine’s anti-anxiety effects come from its increasing alpha brain wave activity. In addition to increasing GABA levels and being an antagonist of AMPA glutamate receptors.

Studies on animals show us evidence of l-theanine crossing the blood-brain barrier and increasing the brains’ serotonin, GABA, and dopamine levels. [Reference]

Increasing levels of those vital neurotransmitters result in a great reduction and a better management of different types of anxiety.

L-theanine’s general calming effects are reflected in increased brain electrical activity in the alpha frequency range 8 to 13 Hz, which are the levels observed during meditation. A 200mg dose of l-theanine shows an increased alpha wave activity for 60 minutes.

It is more effective in people with higher levels of anxiety.

Furthermore, green tea with high l-theanine levels has been proven to reduces adrenal hypertrophy (a group of genetic disorders that affect the adrenal glands) in mice exposed to chronic stress.

Individuals consuming green tea for stress and anxiety experience better calming effects. A calming effect is usually felt within 30 to 40 minutes of taking a dose within the 50 to 200mg range, and lasting anywhere between 8 and up to 10 hours.

Moderate anxiety symptoms often respond to higher dosage of 200mg once or twice a day. While cases of severe anxiety may need a higher dosage of 600mg to 800mg as the total intake per day, taken in 100mg to 200mg intervals throughout the day.

Unlike benzodiazepines (prescription sedative medication), l-theanine does not cause drowsiness or impaired concentration. It has no risk of tolerance or dependence.

There are no reports of severe adverse side effects nor interactions of l-theanine with other medication.

Two studies show the same dose of l-theanine results in reductions of subjective stress measures, such as heart rate and blood pressure.

Adults taking l-theanine experience significant decreases in anxiety levels over a 4-week clinical trial. In comparison to the placebo group, they improved sleep quality as well.

In a small placebo-controlled trial, adults aged 18-40 were given an l-theanine drink vs. placebo before testing a multitasking cognitive stressor. After consuming the drink, the l-theanine group reported a lower stress response than the placebo. [reference]

Another study finds a drink containing 200mg l-theanine, 1mg phosphatidylserine (aka Smart PS), 10mg chamomile, and 25mg glycerylphosphorylcholine (aka Alpha-GPC) reduced stress response within an hour of ingestion. Additionally, it decreased cortisol levels three hours after ingestion. [reference]

L-Theanine on Psychiatric Conditions

In another randomized placebo-controlled study finds taking 100mg of l-theanine twice a day improves sleep quality in ADHD individuals, implying l-theanine could be an effective addition to an ADHD treatment. [reference]

L-theanine does not cause drowsiness, but taking 200mg of l-theanine before bedtime may improve sleep quality.

Recent studies suggest l-theanine may have a beneficial effect on symptoms of depression and psychosis.

In an 8-week study, adults with major depressive disorder treated with l-theanine 250mg per day reported mood, anxiety, and sleep quality improvements. [reference]

Another 8-week placebo-controlled trial found that l-theanine supplementation reduces stress in people with schizophrenia.

Increases in cortisol and brain-derived neurotrophic factor may mediate the beneficial effects of l-theanine supplementation in this population.

L-theanine may also help with anxiety associated with psychosis. And a combination treatment of l-theanine is found to alleviate psychotic symptoms.

A study of a group receiving l-theanine (and pregnenolone) showed fewer symptoms of psychosis, lower anxiety, and improved cognitive function than the placebo group. [reference]

L-Theanine on Cerebrovascular Disease and Stoke

Animal studies show l-theanine helps prevent cerebrovascular disease (a condition that affects blood flow and the blood vessels in the brain).

Furthermore, it reduces the severity of associated risks such as strokes.

The neuroprotective effects of l-theanine may be due to its action as an AMPA glutamate-receptor antagonist (a substance that inhibits physiological activity).

Mice given l-theanine before being subjected to repeated episodes of induced cerebral ischemia revealed significantly less impairment in spatial memory (storage and retrieval of information within the brain) and neuronal cell death. [reference]


L-Theanine is a great natural and safe nootropic offering a wide range of benefits. It’s repeatedly proven to reduce anxiety, enhance sleep, improve cognition, memory, and focus.

Research shows it helps reduce and might prevent stress-related hypertension. It may also be a valuable adjunct therapy for cancer patients.

Suppose you’re interested in an effective natural nootropic with no severe side effects. In that case, L-theanine may be worth a try. Especially if you experience any stress, anxiety, or poor sleep quality.

Further Readings

Scientific Review of Nootropic L-Theanine. Usage, Benefits, Effects, Mechanism of Action, Dosage, Side Effects, User Experiences, and FAQs – Nootropics Information

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