Theanine (as Suntheanine®)

Theanine (as Suntheanine®)
  • Gluten Free
  • Non-GMO
  • Vegetarian
  • Vegetable Caps

Helps moderate stress and promotes a sense of calm and relaxation without drowsiness

  • Supports emotional well-being
  • Eases occasional nervous tension and irritability
  • Supports healthy stress response
  • Promotes positive mood and relaxation
  • Enhances brain GABA production

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Product Information Sheet (PDF)

L-Theanine is a naturally occuring amino acid found almost exclusively in the green tea plant that produces beneficial effects on the brain and nervous system. Tea leaves have been used in traditional medicine as an agent to rejuvenate, relax, enhance the ability to think, and change mood.

Without causing daytime drowsiness, theanine helps promote a calm, relaxed state. It has been shown to stimulate alpha wave production in the occipital and parietal regions of the brain, creating a state of deep relaxation and mental alertness similar to what is achieved through meditation. Alpha activity is known to play an important role in critical aspects of attention. Additionally, L-theanine can enhance the production of the neurotransmitters dopamine and serotonin and appears to play a role in the formation of GABA – a neurotransmitter that reduces neuronal excitability throughout the nervous system and promotes a calming response to stress.

In addition to anti-stress effects demonstrated by L-theanine, studies also point to L-theanine's effect in supporting concentration and in counteracting the negative stimulant side effects from caffeine. It has also demonstrated positive effects on various aspects of sleep quality.

Patient One supplies 200 mg of Suntheanine® brand L-Theanine, a dose supported by clinical research. Suntheanine, a high-purity, L-isomer-specific L-Theanine produced via a patented enzymatic fermentation process, has been found to be most effective in the range of 50-200 mg and its effects are typically exhibited within 30-40 minutes of consumption. 

Increase in Alpha Activity across Time in the L-theanine Condition

16 participants were assigned to the L-theanine group and 19 to the control group. 

The control solution was 100 ml of cool potable water and the L-theanine solution was prepared by dissolving 0.5 mg powdered L-theanine per Kg participant body weight in a tea infusion (total L-theanine 50mg/serving).

L-theanine brain effects

Source:  Anna C Nobre PhD, Anling Rao PhD and Gail N Owen PhD. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr 2008;17 (S1):167-168.


  • In a study of mental responses to L-theanine, brain wave topography showed that alpha waves were observed from the back to the top of a person's head (occipital and parietal regions of the brain) within approximately 40 minutes after the subjects had taken either 50 or 200mg of L-theanine.
  • A double-blind, placebo-controlled study showed that L-theanine intake resulted in a reduction in heart rate and salivary immunoglobulin A responses to an acute stress task relative to the placebo-control condition. Moreover, analyses of heart rate variability indicated that the reductions were likely attributable to an attenuation of sympathetic nervous activation.
  • A randomized, double-blind, placebo-controlled clinical trial demonstrated that 400 mg daily of Suntheanine was effective in improving sleep quality in boys diagnosed with ADHD.
  • A review of studies suggests that caffeinated tea, when ingested at regular intervals, may maintain alertness, focused attention, and accuracy and may modulate the more acute effects of higher doses of caffeine. These findings concur with the neurochemical effects of L-theanine on the brain. L-theanine may interact with caffeine to enhance performance in terms of attention switching and the ability to ignore distraction.


  1. Dufresne CJ, Farnworth ER. A review of latest research findings on the health promotion properties of tea. J Nutr Biochem. 2001 Jul;12(7):404-421. [PMID: 11448616]
  2. White DJ, et al. Anti-Stress, Behavioral and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial. Nutrients 2016, 8, 53; dos:10.3390/nu8010053
  3. Michael R. Lyon, MD, Mahendra P. Kapoor, PhD, Lekh R. Juneja, PhD. The Effects of L-Theanine (Suntheanine?) on Objective Sleep Quality in Boys with Attention Deficit Hyperactivity Disorder (ADHD): a Randomized, Double-blind, Placebo-controlled Clinical Trial. Volume 16, Number 4 Alternative Medicine Review 2011.
  4. Unno K. et al. Anti-stress effect of theanine on students during positive correlation among salivary a-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013 Oct;111:128-35. doi: 10.1016/j.pbb.2013.09.004. Pub 2013 Sep 16.
  5. Anna C Nobre PhD, Anling Rao PhD and Gail N Owen PhD. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr 2008;17 (S1):167-168.
  6. Park SK, Jung IC, Lee WK, et al. A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study. J Med Food. 2011 Apr;14(4):334-43. [PMID: 21303262]
  7. Juneja LR, Chu D-C, Okubo T, et al. L-theanine – a unique amino acid of green tea and its relaxation effect in humans. Trends Food Sci Technol. 1999;10:199- 204.
  8. Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Bill Psychol. 2007 Jan;74(1):39-45. [PMID: 16930802]
  9. Ritsner MS, Miodownik C, Ratner Y, et al. L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. J Clin Psychiatry. 2011 Jan;72(1):34-42. [PMID: 21208586]
  10. Nathan PJ, Lu K, Gray M, et al. The neuropharmacology of L-theanine (N-ethyl- L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother. 2006;6(2):21-30. Review. [PMID: 17182482]
  11. Yamada T, Terashima T, Okubo T, et al. Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutr Neurosci. 2005 Aug;8(4):219-26. [PMID: 16493792]
  12. Sadzuka Y, Inoue C, Hirooka S, et al. Effects of theanine on alcohol metabolism and hepatic toxicity. Bill Pharm Bull. 2005 Sep;28(9):1702-6. [PMID: 16141543]
  13. Li G, Ye Y, Kang J, et al. l-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes. Food Chem Toxicol. 2012 Feb;50(2):363-72. [PMID: 22019691]
  14. Rogers PJ, Smith JE, Heatherley SV, et al. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl). 2008 Jan;195(4):569-77. [PMID: 17891480]
  15. Simon P. Kelly, Manuel Gomez-Ramirez, Jennifer L. Montesi, and John J. Foxe. L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance. J. Nutr. 138: 1572S–1577S, 2008.

Supplement Facts

Serving Size: 1 Capsule
Servings Per Container: 60
Amount Per Serving % Daily Value**


200 mg
† Daily Value not established.

Suggested Use

Take 1 capsule daily, preferably between meals, or as directed by your health practitioner. Store in cool, dry place.


If you are pregnant, nursing, or taking any medications, consult your health practitioner before use. Discontinue use and consult health practitioner if any adverse reactions occur. Keep out of reach of children. Use only if safety seal is intact.

Theanine (as Suntheanine®) Label