The 8+ Benefits of Theanine

The Benefits and Mechanisms of Theanine

Theanine has many benefits that protect the brain and heart, reduce stress, and improve mood. R



L-Theanine or 5-N-Ethyl-Glutamine

L-Theanine or 5-N-Ethyl-Glutamine


Theanine is a non essential amino acid. R

The biological activity of L-theanine is very high in vivo. R

L-theanine is an important bioactive component of tea, and has many physiological functions:

  • regulating immune response R R
  • preventing diseases R
  • anti-tumor R
  • relaxing neural tension R
  • anti-oxidation stress R

Regular brewed black tea contains significantly more L-theanine per cup when compared to commercially available green tea. R

There are a few different sources and forms of theanine:

  • From green tea and fungi such as tea leaves, Japanese Camellia Bay, and Bolster mushrooms R R R
  • I-L-theanine (L-theanine) 
  • D-theanine (competes for absorption) 
  • Suntheanine (manufactured from of L-theanine) 

In The Body

  • Theanine is absorbed in the small intestine after oral ingestion. R
  • Its hydrolysis is to L-glutamate and ethylamine occurs in both the intestine and liver.  R
  • It can also cross the blood–brain barrier intact, and register pharmacological effects directly. R
  • Theanine reaches the brain within an hour remains elevated for up to 5 hours.
  • Theanine promotes alpha-wave production in the brain. R

Mechanisms of Action

  • L-theanine inhibits binding of glutamate to its cortical excitatory neuronal receptors: AMPA, kainate, and NMDA. R
  • The inhibition of glutamate receptor activity is thought to contribute to the anti-stress effects of L-theanine. R R


1. Improves Cognitive Function and Mood


Theanine increases serotonin, dopamine, GABA, and glycine levels in various areas of the brain, as well as BDNF and NGF levels in certain brain areas. R R R R

In combination with caffeine, L-theanine has shown to improve memory and increase attention. R R

L-theanine improved task switching. R

L-theanine and green tea extract helped adults with mild cognitive impairment perform better on memory recognition tests. R

L-theanine with caffeine improves mood within 60 minutes. R

2. Reduces Stress, Anxiety, and Schizophrenic Symptoms

Stress symptoms and heart rates were reduced with L-theanine supplementation. R

Supplementing 400mg of L-theanine for 8 weeks reduced schizophrenic symptoms, anxiety and muscle pains in patients. R

Compared to Xanax, L-theanine was able to promote relaxation in healthy subjects. R

3. Supports The Heart


In European subjects, 3 cups of tea a day was able to reduce the rate of heart attacks by 11%. R

On Japanese subjects, stroke and heart disease were reduced by green, black, and oolong tea consumption, compared to coffee drinkers. R

L-theanine lowers blood pressure. R

4. Increases Sleep Quality  


Doses of 200mg of L-Theanine twice a day for 6 weeks improved the quality of sleep of ADHD boys. Supplementation also helped decrease sleep onset and increase sleep percentages. R

5. Has Antioxidant Properties 

In certain doses, L-theanine from green tea has antioxidant properties. R 

L-theanine through antioxidant and anti-inflammatory actions reduced bladder hyperactivity. R

L-theanine protected against liver toxicity from alcohol. R

By inhibiting NF-κB and TGF-β, L-theanine was able to prevent liver fibrosis. R

L-theanine is able to decrease oxidative damage and stopped inflammation. R

6. Has Antihistamine Properties

Histamine release from mast cells was decreased with the treatment of theanine and might possess mast cell-stabilizing capabilities. R

Theanine inhibited mast cell mediated anaphylactic reactions. R

7. Improves Immune Function

In humans, ingestion of L-theanine by drinking tea induces innate immune response and immunologic memory. R

In rats, administration of 400 mg/kg BWL-theanine improved immune function by R

  • increasing the splenic weight
  • altering the TH1/TH2 balance
  • decreasing the corticosterone levels
  • elevating dopamine and serotonin in the brain
  • regulating the mRNA expression of PLC isomers in the heart

8. Neuroprotective

L-theanine provided neuroprotection against Parkinson-related neurotoxicants. R

It may be useful for preventing PD symptoms. R

My Experience


I originally supplemented with l-theanine because I had high levels of TGF-beta 1. 

With L-theanine my blood pressure was reduced and I also had a calm but alert sense of focus and clarity.  I take it on an empty stomach, in the morning and evening. 

Where to Get Theanine


I prefer not to get theanine from tea, since tea is high in tannins. 

I use Suntheanine from Doctor's Best.  

When I make Super Coffee, I use the pure powder.

Doses are health and age-dependent. R  

According to research from the University of Newcastle in Australia, the best way to get L-theanine from tea: R

  1. Steep tea at 80 degrees Celsius for 30 minutes
  2. Use water to tea ratio of 20 ml per 1 gram
  3. Steep tea that is between 0.5 and 1 mm in particle size

Side Effects


L-theanine can cause headaches and digestive discomfort. R

It can also reduce the effects of stimulants. R

More Research

  • Promotes anti-inflammatory IL 10. R
  • Can prevent hepatotoxicity from doxorubicin. R 
  • May inhibit glutamate excitotoxicity. R
  • In weaning piglets, treatment of β-glucan and L-theanine lessened the inflammatory responses against Gram-negative bacterial infection by inhibiting pro-inflammatory cytokines hyperproduction, while enhancing anti-inflammatory cytokine production. R
  • L-Theanine prevented increased expression of NF-κB and down-regulated the pro-inflammatory (interleukin (IL)-1β and IL-6) and profibrotic (TGF-β and CTGF) cytokines. R
  • Under emotional arousal, caffeine and theanine exert opposite effects on certain attentional processes, but when consumed together, they counteract the effects of each other. R
  • Long-term green tea supplementation does not change the human gut microbiota. R
  • Top 6 Proven Health Benefits of Theanine R
  • L-theanine at a particular dose range increases sensorimotor gating in humans R