L-Theanine
What is L-Glutamine?
L-Theanine is an amino acid that can be found in tea leaves and supplements. It promotes relaxation, sleep and improved cognition.
L-Theanine is a non-essential amino acid that can be found in nearly all tea leaves, but it is especially abundant in green tea. [1] Amino acids are the building blocks of proteins however, L-theanine is one amino acid that is not used to build protein.
L-Theanine is an antioxidant that can cross the blood-brain barrier. It has a chemical structure that is very similar to glutamine, which is used to make glutamate.
Glutamate is the most abundant neurotransmitter in the human body and typically has an excitatory effect. L-theanine uses the same receptor sites as glutamate, since they have similar structures, so the two actually compete for those receptor sites. This is why L-theanine has a calming and relaxing effect, because it reduces the amount of glutamate that can bind to those receptor sites. [4]
The effects of L-theanine include reduced stress and anxiety, improved sleep as well as improved cognition and attention.[1,3] It is thought that L-theanine enhances the neurotransmitters involved in these processes. For example, the neurotransmitter serotonin is enhanced with L-theanine and in the brain, serotonin is converted to melatonin. Put simply, more serotonin leads to more melatonin which leads to more restful sleep. [2]
L-theanine is generally safe, with minor reported side effects like nausea and gastrointestinal upset if taken in large doses. [1,7]
There is an interaction between L-theanine and midazolam, which is a sedative often given before surgery. [1]
Studies suggest that L-theanine administered at daily doses ranging from 200 to 400 mg for up to 8 weeks are safe in both adults and children. Higher and lower doses may be effective as well, but more research is needed to support this claim. [11]
Sources of L-Theanine
L-theanine is found in green, black, white, and oolong tea leaves, and supplements (see below).
Is L-Theanine Benenficial for Autism?
L-Theanine and Cognition
L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.[3]
L-Theanine-caffeine combination may be a potential therapeutic option for ADHD-associated impairments in sustained attention, inhibitory control and overall cognitive performance. [5]
Our study indicated that l-theanine may contribute to improving attention, thus enhancing working memory and executive functions. [10]
L-Theanine and ASD
These results suggest that sensorimotor abilities, anxiety levels and DSM-5 symptomology of children with ASD can benefit from the administration of GABA in the form of Oolong tea, which is high in L-theanine. [6]
L-Theanine and Sleep
ABA/l-theanine mixture has a positive synergistic effect on sleep quality and duration as compared to the GABA or l-theanine alone. [7,9]
This study demonstrates that 400 mg daily of L-theanine is safe and effective in improving some aspects of sleep quality in boys diagnosed with ADHD. Since sleep problems are a common co-morbidity associated with ADHD, and because disturbed sleep may be linked to the cause to this disorder, L-theanine may represent a safe and important adjunctive therapy in childhood ADHD. [8]
L-theanine and Depression
Our study suggests that chronic (8-week) l-theanine administration is safe and has multiple beneficial effects on depressive symptoms, anxiety, sleep disturbance and cognitive impairments in patients with Major Depressive Disorder. [12]
Supplementation
Supplements for L-theanine are available in a variety of forms and dose is dependent on weight and the needs of each unique child.
Examples of common L-theanine supplements include:
Powder
Liquid
Thorne also offers little flavored discs that dissolve in water that contain theanine. These are not available through Amazon but can be accessed through a professional-grade supplement dispensary like Fullscript or Wellevate.
Capsule/Softgel
DISCLAIMER: Before starting any supplement or medication, always consult with your healthcare provider to ensure it is a good fit for your child. Dosage can vary based on age, weight, gender, and current diet.
Note: All supplements are linked to Amazon for convenience, however, buying supplements on Amazon does not guarantee quality, as there are many “unverified resellers” selling nutrition supplements. To buy supplements that are verified to be sent directly to the consumer, you can create an account on the Autism Dietitian FullScript and search for the respective supplement under “Catalog”.
Authors
Edited & Reviewd by: Brittyn Coleman, MS, RDN/LD, CLT
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[1] L-theanine. Memorial Sloan Kettering Cancer Center. Accessed January 29, 2022. https://www.mskcc.org/cancer-care/integrative-medicine/herbs/l-theanine
[2] L-theanine for sleep and stress. What does the science say? Thorne.com. Accessed January 29, 2022. https://www.thorne.com/take-5-daily/article/-l-theanine-for-sleep-and-stress-what-does-the-science-say
[3] Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients 2019;11(10):2362.
[4] PubChem. L-Theanine. Nih.gov. Accessed January 29, 2022. https://pubchem.ncbi.nlm.nih.gov/compound/L-Theanine
[5] Kahathuduwa CN, Wakefield S, West BD, et al. Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT. Sci Rep. 2020;10(1):13072.
[6] Hannant P, Cassidy S, Renshaw D, Joyce A. A double-blind, placebo-controlled, randomised-designed GABA tea study in children diagnosed with autism spectrum conditions: a feasibility study clinical trial registration: ISRCTN 72571312. Nutr Neurosci. 2021;24(1):45-61.
[7] Anand S, Tong H, Besag FMC, Chan EW, Cortese S, Wong ICK. Safety, Tolerability and Efficacy of Drugs for Treating Behavioral Insomnia in Children with Attention-Deficit/Hyperactivity Disorder: A Systematic Review with Methodological Quality Assessment. Paediatr Drugs. 2017;19(3):235-50.
[8] Lyon MR, Kapoor MP, Juneja LR. 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. Altern Med Rev. 2011;16(4):348-54.
[9] Kim S, Jo K, Hong KB, Han SH, Suh HJ. GABA and l-theanine mixture decreases sleep latency and improves NREM sleep. Pharm Biol. 2019;57(1):65-73.
[10] Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. J Med Food. 2021;24(4):333-41.
[11] Lopes Sakamoto F, Metzker Pereira Ribeiro R, Amador Bueno A, Oliveira Santos H. Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia. Pharmacol Res. 2019;147:104395.
[12] Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr. 2017;29(2):72-9.
