Is L-Theanine A Natural Nootropic?

Written by Andy Mobbs
featured image for article on seneca ingredient l-theanine

In this article, you’ll learn all about the amazing health benefits of L-theanine, one of the ingredients in our Seneca Nootropic Complex. You’ll learn how it can reduce stress and anxiety, as well as boost brain health and cognitive function.

What is L-Theanine?

L-theanine is an amino acid that’s found naturally in all teas and some plant extracts but is most abundant in green tea. It’s thought that the theanine content in green tea is the main reason people feel relaxed after drinking it. It’s also used as a supplement to help people cope with stress and reduce their anxiety (1).

This reduction in stress allows people taking theanine to reduce their inflammation, sleep better, and think more clearly.

How does L-theanine work?

One of the main ways that theanine works is by being able to control levels of a neurotransmitter called glutamate. Glutamate’s main role is as an excitatory neurotransmitter. This means it has a ‘switching on’ effect in the brain. And it is key for normal brain functioning as well as focus, learning, and memory.

Reduced Glutamate Toxicity

Nowadays, most of us have access to more than enough calories, meaning we also have more than enough glutamate. This, together with chronic stress and inflammation, can lead to glutamate activating too many receptors in the brain.

This excess activation can become toxic to brain cells, aka neurons. This can lead to damage or even death of the cells, potentially causing many problems. Examples include poor sleep, feeling too wired, and stress. It can also lead to health issues like depression and dementia.

In a process called ‘competitive inhibition’, theanine can reduce excess levels of glutamate. It actively binds at the site on neurons that the glutamate binds to. By doing so, theanine can inhibit glutamate’s ability to activate neurons and become toxic (2, 3).

competitive inhibition

Theanine can also reduce the uptake of glutamine into the neurons. This is the second way that theanine can moderate excess glutamate levels (4).

Increased GABA and Glycine

Theanine doesn’t just help reduce excess levels of glutamate in the brain though. It also helps to increase levels of the neurotransmitters GABA and glycine.

GABA and glycine are both inhibitory neurotransmitters and have the opposite effect to glutamate’s excitatory effects. GABA, for example, can promote feelings of calm and relaxation. Tranquilizer drugs like benzodiazepines (e.g. Valium) work on GABA receptors (5, 6).

Theanine can help to calm down the brain and central nervous system by increasing levels of GABA and glycine.

Increased levels of BDNF

Theanine has also been shown to increase levels of BDNF (brain-derived neurotrophic factor). BDNF is a growth hormone for the brain. It helps the growth and repair of neurons. It also helps with synaptic plasticity, or the ability to be able to form new connections to learn things (7).

Serotonin and Dopamine

Theanine can increase levels of Serotonin and Dopamine in the brain (8). These neurotransmitters are associated with motivation, focus, learning, and feeling good. In fact, low levels of them have all been associated with anxiety and depression.

Increased Alpha Brain Waves

Studies have also shown theanine can increase levels of alpha brainwaves (9, 10). Alpha brainwaves are associated with relaxed focus, better concentration, and improved overall cognitive function.

Show me the Science!

Reduced Stress

A Japanese study gave 12 subjects a mental arithmetic test designed to challenge the participants and create stress. They conducted the test 4 times, with either 200mg of theanine at the start or halfway through. They then compared these results to controls with no supplementation and one with a placebo.

The findings were that heart rate and salivary immunoglobulin A levels were lower in those given theanine (11). Immunoglobulin A is an antibody, and the immune system increases its production during stress.

Another study tested 34 subjects on a further cognitive stress test. Researchers found that those who took 200mg of theanine had lower salivary cortisol levels (12).

Reduced Anxiety

In one study, 400mg of theanine per day was given to patients with schizophrenia. This was in addition to their normal medication. A different group was given a placebo. At the end of the 8-week period, the patients who had received theanine had lower anxiety, lower cortisol measures, lower dysphoric mood measures (i.e feelings of anger, depression, irritability), and increased levels of BDNF (13).


20 patients suffering from major depressive disorder were given 250mg of theanine per day for 8 weeks, in addition to their current medication. At the end of the 8-week period, the researchers found that the patients scored lower on markers of depression, had lower anxiety, better quality sleep, and had improved cognitive function and memory scores (14).

Reduced Blood Pressure

Caffeine can increase blood pressure. However, taking theanine with caffeine can prevent a caffeine-induced increase in blood pressure (15).

A further study showed that theanine could prevent the increase in blood pressure that happened during cognitive tests designed to invoke a stressful response (16).

L-Theanine Helps Improve Memory

a bottle of seneca nootropic complex
L-Theanine is one of the ingredients in our Seneca Nootropic Complex

91 subjects with mild cognitive impairment, which is considered the first stage when symptoms of dementia become apparent, were enrolled in a randomized, double-blind study. Half took 1680mg of theanine per day for 16 weeks.

At the end of the study period, the subjects who had taken the theanine scored better on memory tests than those who had taken the placebo. The theanine group also showed signs of theta brain waves which are related to a high level of cognitive awareness and something that advanced meditators strive to achieve (17).

Alzheimer’s disease

In addition to mild cognitive impairment, there has been a further study looking at a mouse model of Alzheimer’s and the effects of theanine supplementation on it.

In the study, researchers injected amyloid beta proteins into the brains of mice. Amyloid-beta proteins form the basis of amyloid plaques found in the brains of Alzheimer’s patients. The process of injecting the amyloid-beta proteins creates neuronal cell death. It then causes memory impairment, effectively giving the mice Alzheimer’s. The researchers then added theanine to the drinking water of half the mice for 5 weeks.

They found that the group that was given theanine performed better on memory tests than the group that wasn’t. Also, after dissecting the brains of the mice, they found less neuronal cell death and oxidative damage to the proteins and lipids in the brains of mice given theanine. They also found higher levels of the body’s main antioxidant glutathione in the supplemented mice, indicating an upregulation of antioxidant production.

Obviously, these types of studies can’t be performed on humans. You can’t inject amyloid-beta proteins into human brains. However, it provides exciting results that will hopefully pave the way for more studies on theanine supplementation in Alzheimer’s patients (18).

Improved Sleep

A placebo-controlled trial on 98 8-12-year-old boys that had been diagnosed with ADHD looked at whether theanine could help improve their sleep (this is often affected in ADHD). Half the participants were given 100mg of theanine per day for 6 weeks. At the end of the 6-week period, the researchers found high sleep percentages and sleep efficiency scores in the group that supplemented with theanine (19).

A further study gave 17 patients with schizophrenia 250mg of theanine per day for 8 weeks in addition to their normal antipsychotic medication. Researchers also found an improved quality of sleep in the patients (20).

Final thoughts

L-theanine’s benefits go beyond reducing stress and anxiety. It can also help improve focus, learning, and memory, amongst many other benefits. Because of L-theanine’s science-backed brain benefits, we’ve added it to our Seneca Nootropic Complex.

Seneca is a non-stimulating nootropic and cognitive-enhancing supplement. Each serving contains 200mg of L-theanine HCL, along with 17 other natural nootropics formulated to boost mental health and restful sleep.

Related article: Seneca Nootropic Complex 101: What Makes This Nootropic Stack So Good?


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(8) L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety, Duygu Türközü, Nevin Şanlier, Crit Rev Food Sci Nutr . 2017 May 24;57(8):1681-1687.

(9) L-theanine, a natural constituent in tea, and its effect on mental state, Anna C Nobre, Anling Rao, Gail N Owen, Asia Pac J Clin Nutr . 2008;17 Suppl 1:167-8.

(10) Effects of Theanine on the Release of Brain Alpha Wave in Adult Males, Song CH, Jung JH, Oh JS, Kim KS, Korean J Nutr. 2003 Nov;36(9):918-923.

(11) L-Theanine reduces psychological and physiological stress responses, Kenta Kimura, Makoto Ozeki, Lekh Raj Juneja, Hideki Ohira, Biol Psychol . 2007 Jan;74(1):39-45.

(12) Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial, David J White, Suzanne de Klerk, Nutrients . 2016 Jan 19;8(1):53.

(13) Serum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patients, Chanoch Miodownik, Rachel Maayan, Yael Ratner, Vladimir Lerner, Leonid Pintov, Maria Mar, Abraham Weizman, Michael S Ritsner, Clin Neuropharmacol . 2011 Jul-Aug;34(4):155-60.

(14) Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study, Shinsuke Hidese, Miho Ota, Acta Neuropsychiatr . 2017 Apr;29(2):72-79.

(15) Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together, Peter J Rogers, Jessica E Smith, Susan V Heatherley, C W Pleydell-Pearce, Psychopharmacology (Berl) . 2008 Jan;195(4):569-77.

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(17) 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, Sang-Ki Park, In-Chul Jung, Won Kyung Lee, Young Sun Lee, Hyoung Kook Park, Hyo Jin Go, Kiseong Kim, Nam Kyoo Lim, Jin Tae Hong, Sun Yung Ly, Seok Seon Rho, J Med Food . 2011 Apr;14(4):334-43.

(18) l-Theanine, an amino acid in green tea, attenuates beta-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-kappaB pathways, Tae Il Kim, Yong Kyung Lee, Sang Gi Park, Im Seop Choi, Jung Ok Ban, Hyoung Kook Park, Sang-Yoon Nam, Young Won Yun, Sang Bae Han, Ki Wan Oh, Jin Tae Hong, Free Radic Biol Med . 2009 Dec 1;47(11):1601-10.

(19) 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, Michael R Lyon, Mahendra P Kapoor, Lekh R Juneja, Altern Med Rev . 2011 Dec;16(4):348-54.

(20) Effect of L-theanine on glutamatergic function in patients with schizophrenia, Miho Ota, Chisato Wakabayashi… Acta Neuropsychiatr . 2015 Oct;27(5):291-6.