L-Theanine: Tea’s Amino Acid for Overall Wellness | campus.sg

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Tea: coffee’s coy competitor in the cutthroat—yet throat-soothing—world of hot beverages. Both provide daily stimulant boosts, both are great to share with a loved one, and both are steeped in rich and complex histories.

But popular teas (like green tea, black tea, and even tea extract and tea constituents) have something coffee doesn’t—an amino acid celebrated for its cognitive performance and wider health benefits: L-theanine (pronounced L-THEE-uh-neen).

The tocopherols and flavonoids in green or black tea lend the cup its signature colour and flavour. The tea leaves’ distinct bitterness is supplied by natural antioxidants knowns as catechins.

But there’s another flavour: umami, which is provided by the non-protein amino acid, L-theanine which is shown to have positive benefits on your stress levels, cognitive performance, and cardiovascular and immune health.

Stress and Anxiety

Researchers have found L-theanine can reduce our physiological stress responses by altering the behavior of neurotransmitters in the brain instantly.

Our brains balance activity through excitatory (upper) and inhibitory (downer) neurotransmitters like dopamine and serotonin. But an excess of these excitatory neurotransmitters can cause classic responses we’re familiar with: stress and anxiety.

L-theanine can inhibit these excitatory responses and ease their physiological stress responses, leading to a lower heart rate, lower blood pressure, and reduced cortisol levels (major stress hormone).


During sleep, it’s all about theta waves and delta waves. Theta waves occur in the first stages of sleep; Delta waves are generated during the deepest stages of sleep. But right before sleep, when you’re still in that daydreamy, relaxed state, it’s all about the alpha waves. The brain generates alpha waves during deeply relaxing activities, such as meditation.

Studies have shown that L-theanine can generate alpha brain waves, leading to a prolonged calming effect. In a study of young individuals with ADHD, L-theanine proved effective in helping them experience deep sleep. Other research found that L-theanine improved sleep quality for those diagnosed with schizophrenia.

While you may benefit from taking L-theanine contained in tea before bed, caffeine is a sneaky stimulant. Luckily, there is a lot of tea brands that produce decaffeinated tea these days – from plain black tea to flavoured ones like Earl Grey and more. And you can find them at local supermarkets.

Focus and Attention

L-theanine has the power to both calm you down in the evenings and provide a boost in the morning. Multiple studies show that consuming L-theanine can increase focus, reaction times, and visual processing while reducing mental fatigue.


To be clear: drinking a single cup of green tea will not suddenly remind you of where you left your keys. However, consuming L-theanine over time could help protect the neurons in your brain from cognitive impairment and contribute to the development of the part of your brain responsible for storing memories.

Start young, and you could even stand a better chance against the memory impairment of Alzheimer’s.

Since L-theanine reduces cortisol levels (which negatively impact memory retrieval), you may be able to retrieve those memories a little more easily.

Immune System

L-theanine has been linked to increased protection against the flu and a boost in immune function when combined with another amino acid, L-cystine. This combination improves the production of the antibody Immunoglobin G (IgG), and the antioxidant glutathione (GSH).

Antioxidants are valuable because they help our bodies remove free radicals (molecules that steal from our cells, causing tissue and muscle damage that contributes to diseases like diabetes, heart disease, and cancer). L-theanine has demonstrated powerful antioxidative properties.

Cardiovascular System

Tea leaves from green tea and black tea on their own have been shown to improve cardiovascular health, and has the ability to lessen strain on the heart.

Originally published on HVMN .