L-Theanine 100mg 60 Caps by Metabolic Maintenance

L-Theanine is a non-protein amino acid found naturally in the green tea plant (Camellia sinensis). It is an effective GABA precursor and supports healthy relaxation without drowsiness. Because it can cross the blood-brain barrier, L-theanine helps increase brain dopamine levels and helps support a normal immune system. *

  • Protects nerve cells*
  • Enhances focus and attention*
  • Reduces stress response*

Each size 1 vegetarian cellulose capsule contains:


L-Theanine (Suntheanine®)

100 mg


300 mg


What is L-Theanine?

Pure L-Theanine (Suntheanine®) is a non-protein amino acid found naturally in green tea. While amino acids are often referred to as “building blocks for protein” there are some amino acids that function independently without contributing to protein structures. L-Theanine is one of these “non-protein” amino acids.

L-Theanine supports healthy relaxation without drowsiness. It can be credited, in part, for the calm sense of focus brought on by drinking green tea. It has been extensively studied for its potential to reduce stress, boost mood, improve cognition, and enhance immune response.

Our formula also contains glycine, another calming amino acid, which acts as a major inhibitory transmitter in the central nervous system and is known to promote healthy sleep patterns.


How does L-Theanine Work?

Once absorbed, supplemental l-theanine crosses the blood-brain barrier, where it can contribute to an increase in GABA, serotonin, dopamine, and glycine in various regions of the brain [1]. It also increases BDNF (brain-derived neurotrophic factor), which can elicit antipsychotic and antidepressant effects, as well as NGF (nerve growth factor), and thus may have an overall neuroprotective ability [2]. L-Theanine has been shown to promote alpha-wave activity in the brain, a measurable indicator of relaxation [3].

Studies have shown that l-theanine can also regulate the secretion of immune cytokines, thus enhancing innate immune function [4]. An l-theanine metabolite, ethylamine, also supports immune function by priming gamma-delta T cells, the first line of defense against many types of infection [5]. 

L-Theanine may also have hepatoprotective qualities, by enhancing the antioxidant activity of liver cells [6].

As a major inhibitory neurotransmitter in the central nervous system, glycine exerts postsynaptic inhibition that is important for control of the excitability of motor neurons, auditory processing, pain transmission and other functions [7]. When supplemented at bedtime, glycine also promotes healthy sleep patterns, decreases daytime sleepiness, and has been shown to improve patient performance on memory recognition tasks [8].


What are the Suggested Uses for L-Theanine?

  • Nerve cell and signaling protection - Protects nerve cells by increasing BDNF and NGF expression, and neurotransmission by increasing GABA, serotonin, and dopamine. 
  • Enhanced focus and attention.
  • Reduced stress response - calms and quiets the nervous system with inhibitory neurotransmitters.


Source Materials: L-Theanine is derived from L-Glutamine via an enzymatic process. Glycine is synthetic. Cellulose for capsules is derived from softwood tree pulp. All ingredients are vegan and non-GMO.


Allergens:  According to information provided by our suppliers, these capsules are free of the eight major allergens as identified by the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA): Wheat (gluten), eggs, milk, soybeans, shellfish, fish, peanuts, tree nuts.


Recommendations: One (1) capsule daily, or as directed by a healthcare professional. Best taken between meals.


Precautions: Pregnant or lactating women and individuals taking prescription medications should consult with a healthcare professional before taking any supplement.



  1. Nathan, Pradeep J., et al. "The neuropharmacology of L-theanine (N-ethyl-L-glutamine) a possible neuroprotective and cognitive enhancing agent." Journal of Herbal Pharmacotherapy 6.2 (2006): 21-30.
  2. Wakabayashi, Chisato, et al. "Behavioral and molecular evidence for psychotropic effects in L-theanine." Psychopharmacology 219.4 (2012): 1099-1109.
  3. Kobayashi, K., et al. "Effects of L-theanine on the release of alpha-brain waves in human volunteers." Journal of the Agricultural Chemical Society of Japan (Japan) (1998).
  4. Li, Chengjian, et al. "L-Theanine improves immunity by altering TH2/TH1 cytokine balance, brain neurotransmitters, and expression of phospholipase C in rat hearts." Medical science monitor: international medical journal of experimental and clinical research 22 (2016): 662.
  5. Bukowski, Jack F., Craig T. Morita, and Michael B. Brenner. "Human γδ T cells recognize alkylamines derived from microbes, edible plants, and tea: implications for innate immunity." Immunity 11.1 (1999): 57-65.
  6. Li, Guilan, et al. "L-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes." Food and chemical toxicology 50.2 (2012): 363-372.
  7. Benarroch, Eduardo E. "Glycine and its synaptic interactions: functional and clinical implications." Neurology 77.7 (2011): 677-683.
  8. Yamadera, Wataru, et al. "Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes." Sleep and Biological Rhythms 5.2 (2007): 126-131.


* These statements have not been evaluated by the Food & Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.