L-theanine Health Benefits and Side Effects

L-theanine is an amino acid that occurs naturally in tea leaves. It promotes relaxation & stabilizes cognitive function influenced by stress hormones.

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What is L-theanine?

L-theanine (γ-N-ethylglutamine) is an amino acid that occurs naturally in tea leaves and from the edible bay boletes mushroom Xerocomus badius. Green tea and black tea are created from the very same plants. Black tea is produced through fermentation, but green tea isn’t fermented. Green tea has been a mainstay of Chinese medicine for over three millenniums and is used medicinally in conjunction with other herbs and independently in a concentrated liquid to enhance endurance and endurance. The quantity of l-theanine depends on where tea plants have been grown, manufacturing procedures, and the time of harvesting. Various species of tea like Camellia sinensivar have greater concentrations of l-theanine compared to more recognizable C. Sinensis. A synthetic form of L-theanine (Suntheanine™) is also available.

L-theanine is widely used in Asian countries to treat an assortment of health and mental health issues and is quickly gaining popularity in Western countries. Caffeine, the other significant constituent of tea, raises brain levels of acetylcholine and dopamine, leading to enhanced focus, cognition, and mood. 

How does L-theanine work?

Finding ways to prevent burnout became the focus of many health-care schools and institutions. Many health-care bodies and groups have implemented wellness programs and formed committees charged with improving work conditions and decreasing stress in doctors.

If you’re contemplating adding L-theanine to your everyday health routine, a dose of 100- 400 mg is recommended, starting with the lowest dose and slowly increasing until feeling the effects. Always consult your doctor before starting any new dietary changes.

L-theanine benefits for brain health

Many wellness programs rely on peer interaction and might take time to execute and achieve results; however, doctors can work to enhance their mental health now by choosing a dietary supplement that’s been shown to ease tension and anxiety.

– Cognitive function

In addition to promoting relaxation, L-theanine was proven to stabilize cognitive function influenced by stress hormones. More specifically, L-theanine reduces corticosterone levels, which, when elevated, can inhibit spatial learning and memory formation. Other researchers have demonstrated that, in people with stress, L-theanine improved attention span and response time. Taken with caffeine, L-theanine enhanced visual information processing and precision when moving between jobs. L-theanine has also been proven to enhance the time to sleep in addition to the quality of sleep. Rather than acting as a sedative, L-theanine functions to encourage better rest by reducing stress and promoting comfort.

– Anxiety & Stress

L-theanine, a water-soluble, non-protein amino acid commonly found in green tea and a few mushrooms, has been widely studied for its ability to encourage wakeful relaxation without sedation. L-theanine is supposed to function by decreasing “excitatory” brain chemicals that promote anxiety and anxiety while increasing brain chemicals that promote a feeling of calm. It has even been proven to reduce stress-related blood pressure and heart rate.

On their site, Memorial Sloan Kettering Cancer Center breaks down L-theanine’s proposed mechanism of action. L-theanine crosses the blood-brain barrier, also can regulate inhibitory neurotransmitters, selective serotonin, and dopamine to lead to anxiolytic and calming effects. L-theanine may also enhance cognition and selective attention, possibly due to changes in alpha brain wave activity. Ultimately, its ability to selectively bind to glutamate receptors can confer neuroprotective effects also.


It might be L-theanine’s ability to stabilize glutamatergic concentrations, which affirms the benefits seen in patients with schizophrenia. Studies demonstrated that L-theanine, together with antipsychotic treatment, improved sleep and eased anxiety.

Weight loss

63 recently published studies outlined the consequences of L-theanine. According to the results of those studies, L-theanine can also assist with weight loss in obese people, improve elevated lipids, and provide neuroprotection and anti-tumor consequences.

– Depression

In patients with major depressive disorder, the nutritional supplement alleviated depression and anxiety symptoms and improved sleep quality and cognitive functioning.

There have been no reported adverse effects connected to L-theanine. Indeed, adults generally tolerate L-theanine well. If you’re contemplating adding L-theanine to your everyday health clinic, a dose of 100-400 mg is recommended, starting with the lowest dose and slowly increasing until you feel the effects. When used in combination with caffeine, consider 12-100 mg of L-theanine to 30-100 mg of caffeine.

L-theanine isn’t a single all-encompassing solution to alleviate stress. An integrative multi-modal strategy is necessary to enhance wellbeing. Nonetheless, L-theanine might be a means to help incorporate more calm into the workday.

L-theanine science & research

Animal and human studies support that L-theanine reduces subjective stress response, enhances cognitive performance, improves sleep quality, and has protective effects against chronic illness, cardiovascular disease, obesity, and the common cold. Various green tea constituents, such as l-theanine, caffeine, and catechins, can help prevent metabolic syndrome and obesity. L-theanine reduces oxidative damage caused by free radicals, raises hemoglobin concentration in the liver, and improves liver enzymes like superoxide dismutase clear toxins from the blood. Research findings indicate that l-theanine has anti-aging advantages. Catechins from green tea may have valuable antimicrobial and antiviral actions. In the gastrointestinal tract, green tea was shown to trigger intracellular antioxidants and inhibit procarcinogens’ formation.

L-theanine and Neuropsychiatric Disorders

L-theanine has been shown to enhance learning, memory, And cognitive function, and increase selective attention during mental tasks. Epidemiological studies support that regular ingestion of tea made from the leaves of Camellia sinensis is associated with decreased prevalence of cognitive decline, improved mood, and improved capacity to deal with stress. L-theanine is a promising enhancement treatment for schizophrenia. It might have beneficial effects on mood disorders, attention deficit hyperactivity disorder (ADHD) and anxiety disorder, obsessive-compulsive disorder (OCD), and bipolar disorder.

Placebo-controlled studies have investigated the consequences of L-theanine alone or in combination with caffeine on mood and cognitive performance, together with the finding that cognitive function is improved in response to combined therapy but not in reaction to l-theanine alone. Two meta-analyses of human interventions on severe psychoactive effects of tea components on mood and cognitive performance discovered signs that l-theanine enhances self-reported comfort, reduces subjective feelings of anxiety. That caffeine enhances performance on demanding cognitive tasks and enhances alertness and vitality.

Animal studies support that L-theanine quickly crosses the blood-brain barrier, increases brain serotonin levels, GABA, and dopamine, binds to glutamate and NMDA receptors, and might raise levels of brain-derived neurotrophic factor (BDNF). Long-term usage of l-theanine (i.e., more than 3 months ) may have overall neuroprotective benefits mediated by increased synthesis of brain-derived neurotrophic factor (BDNF) in the hippocampus that an area of the brain which plays a central role in memory consolidation. All these effects are thought to result in stress reduction. As L-theanine is typically Ingested together with caffeine and other bioactive components of tea, most studies have investigated the joint effects of l-theanine and caffeine on mood and cognition.

L-theanine, Stress, and Anxiety

L-theanine’s anti-anxiety ramifications are mediated through distinct mechanisms, Including improved alpha brain wave activity, increased synthesis of GABA, and its position as a weak antagonist of AMPA glutamate receptors. General calming advantages of l-theanine are reflected in increased brain electric activity in the alpha frequency range (8 to 13 Hz). Changes in brain electrical activity measured by electroencephalography (EEG) are dose-dependent. They are very similar to beneficial EEG changes observed in meditation, such as increased alpha waves in the occipital and parietal areas. The higher alpha activity was shown to last for 60 minutes after administration of a 200mg dose of l-theanine, and this effect was more marked in people with higher trait anxiety. In the end, the ingestion of green tea with higher l-theanine content has been proven to reduce adrenal hypertrophy in mice exposed to chronic stress.

Individuals who drink green tea for anxiety or anxiety may experience greater calming effects than stimulating effects based upon the relative amounts of L-theanine and caffeine in the specific tea species and how it’s prepared. An overall calming effect is usually noticed within 30 to 40 minutes after L-theanine, a dose of 50 to 200mg that typically lasts 8 to 10 hours. Moderate signs of stress often respond to a routine of 200mg once or twice per day. More severe anxiety may require 600mg to 800mg daily, taken in increments of 100mg to 200mg spaced daily. Unlike benzodiazepines and other prescription antipsychotic drugs, L-theanine doesn’t cause drowsiness or impair concentration. There’s not any chance of developing dependence or tolerance. There are no reports of severe adverse side effects or interactions involving l-theanine and psychotropic drugs or other organic products.

In a 10-week placebo-controlled Study (N=46), adults using a DSM-5 diagnosis of Generalized Anxiety Disorder were randomized to receive l-theanine (450 to 900mg/day) vs. placebo when continuing in their current medication. The adjunctive l-theanine group failed to outperform the placebo group on stress reduction measures or improved sleep quality. In a tiny placebo-controlled study (N=34), healthy adults aged 18-40 were administered an l-theanine beverage vs. placebo then exposed to a multitasking cognitive stressor. The l-theanine group reported significantly lower anxiety responses than the placebo one hour after eating the beverage. Another study on a nutrient beverage containing l-theanine 200mg, phosphatidylserine 1mg, chamomile 10mg, and glycerylphosphorylcholine 25mg found significantly reduced subjective stress responses 1 hour after ingestion. It significantly reduced serum cortisol levels 3 hours after ingestion.

 L-theanine Cerebrovascular Disease and Stroke

Findings of animal studies suggest that l-theanine might help prevent cerebrovascular disease And mitigate the effect of cerebrovascular accidents (i.e., stroke). Neuroprotective effects of l-theanine following transient cerebral ischemia may Be related to its activity as an antagonist of AMPA glutamate receptors. Rats Treated with l-theanine (0.3 to 1mg/kg) before being exposed to repeated Episodes of experimentally induced cerebral ischemia showed significantly less Impairment in spatial memory and less neuronal cell death. 

L-theanine and Other Psychiatric Disorders

A placebo-controlled study found That l-theanine 100mg twice daily significantly improved sleep quality in boys with ADHD, indicating that l-theanine might be an effective adjunctive treatment in ADHD. L-theanine doesn’t cause drowsiness; however, taking l-theanine 200mg at bedtime may improve sleep quality by reducing anxiety.

They were emerging findings support which l-theanine may have beneficial effects on symptoms of depressed mood and psychosis. Within an 8-week open-label study (N=20), adults diagnosed with major depressive disorder treated with l-theanine 250mg/day reported improvements in mood, anxiety, and sleep quality.

L-theanine may also have beneficial effects on anxiety linked to psychosis. Findings of an 8-week placebo-controlled trial service that l-theanine augmentation in people with schizophrenia and schizoaffective disorder reduces stress levels. The beneficial effects of l-theanine augmentation in this population might be mediated by increases in cortisol and brain-derived neurotrophic factor (BDNF). A combination treatment containing the neurosteroid pregnenolone and the amino acid L-theanine may have beneficial effects on symptoms of psychosis. Within an 8-week double-blind, placebo-controlled trial (N=40), adults with schizophrenia or schizoaffective disorder with suboptimal response to antipsychotics were randomized to pregnenolone (50mg/day) and l-theanine (400mg/day) vs. placebo when continuing on their antipsychotic drugs. At the endpoint, the team getting pregnenolone and l-theanine had significantly fewer negative symptoms of psychosis such as blunted affect, anhedonia, and lack of language, significantly decreased anxiety, and greater improvements are generally functioning, in contrast to the placebo group.


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