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More Theanine, Please

More Theanine, Please

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The calming properties of a tea derivative

Each year the American Psychological Association conducts a survey of stress among Americans. According to their March 2022 report, “The number of people who say they’re significantly stressed… is stunning relative to what we’ve seen since we began the survey in 2007.”[1]

Stress and anxiety are inter-related, and they have substantial impacts on human health.  Persistent stress contributes to hypertension, heart disease, irritable bowel syndrome (IBS), eating disorders, substance abuse, and neurodegenerative diseases.[2],[3],[4] It’s no surprise that people are seeking ways to alleviate stress and improve their quality of life.

Thankfully, L-theanine – an amino acid derived from the tea plant (Camellia sinensis) – is a natural product that may help.[5]

The medicinal properties of tea have been celebrated as far back as 2737 BCE.[6],[7] According to Chinese scholars, “Drinking tea can allow people to acquire a peaceful, relaxed, refreshed and cheerful enjoyment, and even longevity.”[8]

Green Tea leaves – Wikimedia Commons

Modern science confirms the value of tea

Modern science confirms this point of view. A placebo-controlled study published in 2007, for example, showed that six weeks of tea consumption helped people to recover more quickly from a stressful task, leading to lower post-stress cortisol levels and greater relaxation.[9]

Of course, the rituals that surround tea drinking contribute to a sense of calm – but so do the bioactive ingredients found within the tea leaves themselves. The relaxing effect is mainly due to L-theanine (N-ethyl-L-glutamine). This natural amino acid is found in Camellia sinensis, the evergreen shrub that is used to produce black, green, and oolong teas.[10],[11],[12]

L-theanine’s chemical structure is similar to glutamate, the primary excitatory neurotransmitter in the central nervous system.[13] Glutamate plays a key role in stress responses via the hypothalamic-pituitary-adrenal (HPA) axis. Theanine decreases cortisol levels by inhibiting this response.[14],[15],[16]

L-theanine also increases gamma aminobutyric acid (GABA)-A, the principal inhibitory neurotransmitter in the human brain.[17] The combination of these effects produces a sense of equanimity in the face of stress.[18],[19]

Theanine counteracts the effects of stress

Stress stimulates the nervous system to produce large amounts of vasoconstricting hormones that increase blood pressure. Fortunately, L-theanine can reduce heart rate and blood pressure during stressful events and mentally challenging tasks, especially in those who are prone to anxiety.[20],[21],[22]

L-theanine can reduce heart rate and blood pressure during stressful events and mentally challenging tasks.

In one study, human volunteers were asked to perform a challenging mental task, and L-theanine helped lower blood pressure and tension-anxiety scores in those whose blood pressure increased during the task.[22]

Similar anti-anxiety effects have been seen in many animal and human studies.[13],[14],[20],[22] In another study in which volunteers were asked to complete a challenging mental test, a dose of 200 mg L-theanine reduced heart rate, subjective stress scores, and salivary immunoglobulin A (IgA) levels (an objective marker of stress).[20]

Similarly, in students training for pharmacy practice, supplemental L-theanine reduced subjective stress levels.[23] Theanine also lowered salivary α-amylase activity, a marker of sympathetic nervous system activity and the “fight or flight” response.

Human electroencephalograph (EEG) studies have shown that alpha brain waves are generated within 40 minutes after the oral administration of theanine (50-200 mg).[11],[12],[22] Alpha brain-wave activity is indicative of relaxation, as well as increased creativity, better performance under stress, and improved learning and concentration.[24],[25] (For comparison, 200 mg of theanine is equivalent to about eight cups of black tea, so it takes a lot of tea to equal the effects of one L-theanine capsule.)[26]

Theanine sharpens the mind

Tea contains caffeine and L-theanine, in a ratio of 2:1 to 4:1, depending on the type of tea and its method of preparation.[24],[27] Although moderate doses of caffeine can sharpen the mind, the presence of caffeine counteracts the relaxing effect of L-theanine.[28]

Remarkably, a single 200 mg dose of L-theanine can increase our ability to concentrate, albeit by a different mechanism than caffeine – and one that does not raise blood pressure.[29]

Multiple clinical trials have confirmed that L-theanine sharpens human attention.[10],[22],[30],[31],[32] (Attention is defined as the concentration of awareness on certain phenomena to the exclusion of other stimuli.)

L-theanine allows individuals to focus their attention more efficiently on their goals, without getting distracted.

Electrophysiological recordings in humans confirm that theanine has a specific effect on the brain’s attention circuitry, enabling the brain to sustain attention throughout difficult or tedious tasks.[33],[34],[35] The net result is that L-theanine allows individuals to focus their attention more efficiently on their goals, without getting distracted.[32] 

Dr. Andrew Scholey, Professor of Human Psychopharmacology at Monash and Swinburne Universities (Melbourne, Australia), believes that this meditative state is achieved by L-theanine’s ability to relax only the areas of the brain that are not needed to perform the task at hand.[36] “The upshot of L-theanine’s effects is a relaxed, capable state of mind – you are in the zone,” says Scholey.[36]

In a study of generally healthy adults, consistent L-theanine administration (200 mg/day for four weeks) increased verbal fluency and decision-making functions, while improving overall mood.[37] Theanine’s ability to boost mood is due in part to an increase in the neurotransmitter dopamine.[16],[18],[38]

Theanine supports and protects the brain

Multiple lines of investigation suggest that drinking tea (and/or consuming L-theanine) may protect the brain against chronic stress, aging, and cognitive decline.[5],[31],[39],[40],[41],[42],[43],[44]

Among other effects, L-theanine turns on genes that promote the regeneration of brain neurons.[45],[46],[47] L-theanine also boosts the expression of brain-derived neurotrophic factor (BDNF), a protein that enhances learning and memory.[26],[48],[49] Therefore, theanine has the potential to reduce the risk of Alzheimer’s disease and other neurodegenerative conditions.” [5],[46]

L-theanine turns on genes that promote the regeneration of brain neurons.

Consistent with these findings, a double-blind, placebo-controlled trial showed that a combination of green tea extract (GTE) and L-theanine significantly improved memory in adults (with an average age of 58) with mild cognitive impairments.[50] In this study, the participants took two supplement capsules twice daily for 16 weeks, with each capsule providing 360 mg GTE and 60 mg L-theanine.[50]

L-theanine also slows the progression of Parkinson’s disease in animal models.[51],[52],[53] According to a recent review, “This unique amino acid bears a potential to ameliorate the pathophysiological changes associated with Parkinson’s disease as it displays antioxidant and anti-inflammatory properties, improves motor behavioral abnormalities, increases dopamine availability, and may cause a favorable downshift in neurodegeneration due to glutamate excitotoxicity.”[54]


In conclusion, L-theanine is a popular supplement that is used to facilitate relaxation, improve mood, counteract stress, and actively support brain health and cognition. If stress is impacting your quality of life, you may want to give L-theanine a whirl.


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