Robyn Tse, RN, RNCP


There are many health benefits to green tea, including its potency of L-theanine – a natural substance gaining traction for its potential to improve stress, cognition, and sleep quality. Green tea is definitely an item you want to add to your pantry after reading this article!

What is L-Theanine?

L-theanine is a unique amino acid found almost exclusively in the tea plant (Camellia sinensis) and mushrooms. The traditional, therapeutic use of tea dates back to China 4700 years ago, and, second only to water, it is the most popular beverage on the planet.

L-theanine is able to cross the blood-brain barrier within 30 minutes of consumption, giving it the ability to exert potent effects on the brain and nervous system. It has been shown to reduce mental and physical stress, improve cognition, and boost mood. If you’re looking to feel relaxed without the drowsiness, a cup of tea might be just what you need.

Health Benefits of L-theanine

What are the health benefits of L-theanine? Here are some big ways it can reduce stress, promote cognitive function, boost your mood and more.

1. Boost relaxation and reduce effects of stress

The majority of research around L-theanine revolves around its ability to promote relaxation and fight stress without sedation. After consumption, L-theanine crosses the blood-brain barrier and affects cranial activity by influencing alpha waves, a pattern of brain activity seen in relaxed states. Interestingly, a similar effect is seen during deep-state mediation.

In one randomized, triple-blind crossover study, healthy participants were given either 200mg of L-theanine or placebo. To induce stress, a mental arithmetic test was given before and after the dose. After a 7-day washout, participants returned for a second period of crossover and administered the alternate product. The researchers found that L-theanine significantly increased alpha waves compared to placebo in an acute, stressful environment. The changes in brain waves indicate relaxation and suggested a calming response.   

In a recent 2022 study, L-theanine in combination with magnesium, B vitamins, and rhodiola was able to significantly reduce stress in healthy individuals. This suggests a synergistic effect when L-theanine is taken with other stress-busting ingredients. 

2. Bolsters cognitive functioning

L-theanine helps you enter into a relaxed mental state and also helps boost cognitive function during while completing demanding tasks at work. It can be a wonderful adjunctive supplement to take during times of increased cognitive demand. In a 2021 RCT study, L-theanine was able to improve cognitive function in middle-aged and older subjects. A single dose of L-theanine improved reaction time to attention tasks and also increased the number of correct answers and decreased the number of omission errors in memory-related tasks.

In another study, healthy adults were given 200mg of L-theanine or placebo over four weeks to determine possible effects on stress-related symptoms and cognitive function. It was found that L-theanine decreased stress and improved cognition compared to placebo.

3. Supports working memory

Glutamate is an excitatory neurotransmitter that shapes learning and memory. However, excess glutamate can cause neuronal death and impair memory processes. It is thought by some that too much glutamate is linked to neurodegenerative disorders like dementia. L-theanine is thought to be neuroprotective, as it binds to glutamate receptors preventing excess glutamate stimulation of brain cells. By blocking glutamate receptors, it may be useful therapy for long-term brain health.

According to a 2011 Journal of Medicinal Food study, a combination of green tea extract and L-theanine (LGNC-07) increased memory and attention span in participants with mild cognitive impairment. According to the study’s researchers, β€œBrain theta waves, an indicator of cognitive alertness, were increased significantly in the temporal, frontal, parietal, and occipital areas after 3 hours in the eye-open and reading states. Therefore, this study suggests that LGNC-07 has potential as an intervention for cognitive improvement.”

Given that green tea and its constituent, L-theanine, have had a long history of human consumption it is prudent to consider its combination as a nutraceutical candidate for enhancing memory and cognition.

4. Provides mood support

One of the most well-known, therapeutic properties of L-theanine come from its ability to increase the levels of brain neurotransmitters, GABA, dopamine and serotonin which calm down the nervous system. GABA is well-documented to have anti-anxiety effects by blocking impulses between nerve cells in the brain, making it beneficial for stabilizing mood, nervousness, or hyperactivity. In fact, some anti-anxiety medications also work by mimicking the effects of GABA, but have drowsiness as a common side effect. This makes L-theanine a potent mood-supporting element that is calming, yet boosts alertness at the same time.

A systematic review described the effects of L-theanine in green tea on the ability to manage stress and anxiety. The findings suggest that L-theanine supplementation of 200-400mg per day may assist in the reduction of stress and anxiety in people exposed to stressful conditions.

5. May help improve sleep quality

Having a hard time catching some β€œZzzs”? Anxious, racing thoughts can keep some people up at night. L-theanine might be worth a try as it helps you rest by promoting relaxation prior to bedtime and providing a refreshed feeling upon waking up. Some L-theanine supplements also have magnesium or melatonin to further help with relaxation prior to sleep.

Where Can I Find L-Theanine?

1. Diet

The richest sources of dietary L-theanine are present in green, black, and oolong teas. Though L-theanine content varies, a single cup of tea typically contains around 25 to 60 mg of L-theanine. Data shows that L-theanine is not degraded by heat nor with the addition of milks or sugar, meaning that tea as a beverage can be enjoyed by most people while reaping the effects of L-theanine. Some other ideas to include L-theanine in your diet:

2. Supplements

Though the greatest sources of dietary L-theanine are in green, black, and oolong teas most people don’t consume large amounts on a daily basis. For a therapeutic effect, this is where L-theanine supplements can help us out. Dosages range from 50 to 400mg.

Though L-theanine is generally safe and well-tolerated by healthy adults, always consult your doctor or functional medicine practitioner prior to taking L-theanine supplements. You will be able to review potential interactions and find the best solution for your unique health profile.

To your good health,

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