L-Theanine is an amino acid commonly found in tea. Theanine, together with caffeine, produce a distinct cognitive enhancement profile without the jitters or other side effects. In addition, theanine has many other surprising health benefits. Read this post to learn more about health benefits of theanine.



Theanine is an amino acid that is mostly found in tea leaves and fungi (R).

It is used to help improve mood and lower stress, and to protect the brain and heart (R).

Theanine usually refers to L-Theanine, which has more health benefits compared to D-Theanine.

Health Benefits of Theanine

1) Theanine Reduces Anxiety and Stress


After participants took L-Theanine, they performed mental tasks. Compared to the patients who took a placebo, they had lower stress symptoms, along with reduced heart rates and blood pressure (RR2).

Daily supplementation in schizophrenic patients leads to reduced anxiety (R).

It also promoted relaxation in healthy patients (RR2).

Supplemental doses of theanine that promote relaxation do not cause sedation (R).

In addition, theanine may also have stimulating effects when given at smaller doses, doses that are less than half the doses that promote relaxation (R).

2) Theanine Improves Brain Function

L-Theanine supplementation helps increase attention and improve memory.

In men and women who suffered from minor brain damage, a combination of L-Theanine and green tea extract improved memory during a mental exercise. It did so by increasing delayed recognition during a memory test (R).

The subjects’ attention span and alertness increased during the memory test as well (R).

An improvement in attention has also been noted in healthy people who are prone to anxiety (R).

3) Theanine Reduces Negative Effects of Caffeine and Improves Its Cognitive-Enhancing Effects

Theanine and caffeine are typically found together in tea. A combination of caffeine and theanine together significantly improves alertness, reduce fatigue, and improves task-switching accuracy (R).

High dose caffeine (250 mg, equivalent to 2.5 cups of coffee) has some negative effects, such as jitters and increased blood pressure. Theanine was able to mitigate the increase in blood pressure (R).

L-Theanine decreases the negative and jittery effects of caffeine in rats (R).

However, human studies found that L-Theanine helps reduce caffeine jitters, although the changes were not significant (R, R2).

L-Theanine changes the pharmacological profile of caffeine in humans, as the combination of caffeine and L-Theanine have somewhat different cognitive enhancement effects. (R)

4) Theanine Protects the Heart and Blood Vessels


Theanine improves blood vessel function by increasing nitric oxide production (RR2).

It also prevents fat peroxidation of LDL (low-density lipoprotein), which reduces the risks of hardening of the arteries (R).

Theanine also decreased blood pressure in hypertensive rats (RR2).

5) Theanine Is an Antioxidant

The L-Theanine in tea exerts a dose-dependent antioxidant effect (R).

It also restored the antioxidant capability of liver cells, which helps prevent liver injuries (R).

In rats, it dose-dependently decreased oxidative damage and stopped inflammation (R).

6) Theanine Increases Sleep Quality


ADHD may cause sleep disturbances. Boys who took two 200 mg doses of L-Theanine daily for six weeks had a higher quality of sleep compared to ones who took a placebo (R).

They had higher sleep percentages and better sleep efficiency. Supplementation also decreased the amount of time the participants were awake during the night after sleep started (R).

7) Theanine Reduces Symptoms of Schizophrenia

Taking 400 mg daily for eight weeks resulted in less schizophrenic symptoms. The patients reported lower anxiety, less sensory complaints, and fewer muscle problems (R).

8) Theanine May Enhance Th1 Immunity and Combat Stress-Related Weakened Immunity

Theanine may boost the activity of T cells that protect against infection and tumors (RR2). Theanine shifts the Th1/Th2 balance towards Th1 (R).

The study showed that tea drinkers, when compared to coffee drinkers, had increased production of cytokines by T cells (R).

High cortisol generally suppresses the Th1 immune system and stimulates the Th2 immune system. In the presence of stress, theanine helps to reverse this trend. Theanine decreased suppression of the immune system and inflammation caused by high cortisol from endurance exercise (RR2).

Theanine may help with allergies. It decreased the production of IgE and histamine release from mast cells (RR2).

Studies showed that theanine intake prevents the flu and common cold (R, R2R3).

Theanine intake also alleviates inflammation and promotes recovery after surgery (RR2).

9) Theanine As an Adjunctive Cancer Treatment

Theanine enhanced anti-tumor effects of cancer-killing drugs (RR2).

It also reduced the toxicity of these drugs to healthy tissues (RR2R3).

Theanine decreased growth and migration of liver and lung cancer cells (RR2).

10) Theanine May Reduce Symptoms of Depression

In an open-label study, L-Theanine intake for eight weeks helped with depressive symptoms, anxiety, sleep disturbance, and cognitive impairments in patients with major depressive disorder (R).

11) Theanine Helps with Weight Loss

Theanine, along with other components of green tea, reduced triglyceride and fatty acid levels in the blood.The food intake and body weight decreased in the mice given theanine (R).

12) Theanine May Heal Stomach Ulcers

L-Theanine healed stomach ulcers at a dose of 10 mg/kg body weight, but aggravated ulcers at a higher dose of 40 mg/kg body weight (R).

It alleviated the adverse effects of non-steroidal anti-inflammatory drugs as an antioxidant and by stimulating prostaglandin E production(R).

How Does Theanine Work?

Theanine is able to cross the blood-brain barrier and affect the brain directly. In the brain, it targets brain chemicals that regulate arousal, anxiety, pleasure, and attention (R). 

When administered to rats in the stomach, theanine is found in the blood after one hour, peaks in the brain at five hours, and is completely eliminated at 24 hours (R).

L-Theanine increases brain serotonin and dopamine levels, with possible improvement in memory and learning (R, R2).

It also increases the levels as well as the effectiveness of GABA, the body’s main inhibitory neurotransmitter (R).

Theanine also increases alpha brain wave activity, which causes mental relaxation, concentration, and deep REM sleep (RR2R3).

L-Theanine increases glutathione levels, the body’s most important antioxidant molecule (R).

L-Theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks (R).


  • The kidney preferentially reabsorbed and metabolized L-Theanine. The kidney preferentially excreted D-Theanine (R).
  • Thus, phosphate-independent glutaminase in the kidneys hydrolyzed Theanine (R).
  • L-Theanine augmentation was associated with a reduction of anxiety (P = .015; measured by the HARS scale) (R).
  • According to the 5-dimension model of psychopathology, L-Theanine produced significant reductions on PANSS positive (P = .004) and activation factor (P = .006) scores compared to placebo (R).
  • Stratified analyses showed that LGNC-07 improved memory and selective attention by significantly increasing the Rey-Kim memory quotient and word reading in the subjects with MMSE-K scores of 21-23 (LGNC-07, n = 11; placebo, n = 9) (R).
  • L-Theanine increases brain serotonin, dopamine, and GABA levels with possible improvement in memory and learning (RR2)
  • Theanine exerts neuroprotective effects possibly through inactivation of group 1 metabotrophic glutamate receptors (R).
  • L-Theanine promotes the release of alpha waves related to mental relaxation and concentration in young adults (R).

Natural Sources of Theanine

  • Tea leaves (RR2)
  • Japanese Camellia (green tea) (R)
  • Bay Bolete mushroom (R)

Side Effects of L-Theanine

In animal studies, oral intake of L-Theanine did not produce toxic effects even at very high doses (R).

However, when taking theanine supplements, you should pay attention to your use of other drugs.

Theanine can lower blood pressure. If you take medication for blood pressure, your blood pressure might go too low.

It can also lower the effectiveness of stimulant medications.

The appropriate dosage depends on the user’s age and health.

My Experience with Theanine and Recommendation

Theanine is relaxing for me, but not too sedating. It’s a good relaxer that doesn’t decrease cognitive performance.

I find that 50 to 200 mg of theanine taken daily provides optimal health benefits (R).

I recommend:

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  • Rosalee Adams

    I began taking 200mg midmorning and now take 200mg 1 hour before bed with 1mg melatonin. The change was gradual but has been remarkable in stress reduction and enhancing my mood and much better quality sleep at night……able to get to sleep and stay asleep (both problems before I began the theanine regiment)
    So grateful that my naturopath recommended it.

  • Buks Terblanche

    I have nerve damage and pain every day and 50mg L-theanine and 500mg of slow release magnesium is the only, only, only thing that helps with my pain Stres and 24/7 muscle twitching.It helps! IT HELPS! NO DR DRUGS HAVE EVER HELP ME WITH MY MUSCLE TWITCHING AND PAIN AND STRES.ON A VERY BAD DAY I TAKE 150mg of L-theanine AND 25MG B6 AND 1000MG OF SLOW RELEASE MAGNESIUM. IT HELP WITH MY STRES, PAIN, MUSCLE TWITCHING, MODE AND MEMORY. I THANK GOD FOR L-THEANINE

  • Phill H.

    I wonder if l-theanine is even appropriate for me.?.
    I do have some anxiety & stress, drink a couple cups of coffee
    in a.m., & sleep well. Why, when, & at what dose would this
    benefit me? Sincerely, Phill
    P.S. Is suntheanine the preferred type?

  • Phif

    This supplement is great! i Used to use Ritalin for my a.d.d disorder and now i just use L theanine. This is really a life saver. I feel focus and with no anxiety. Although Ritalin did help me stay focus i did felt slight anxious when it was wearing off. With L theanine there is no wearing off with no anxiousness just calmness and focus

  • bob

    If I wake up during the night…a 100 mg cap of l-theanine will usually allow sleep and sleeping later.

    Using a Fitbit Charge 2 which monitors sleep levels…i usually see longer deep sleep times after taking this. More deep sleep usually results in a more rested feeling after awakening.

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