Health Benefits of L-Theanine

In this article, I share the many health benefits of L-Theanine. The best source of L-Theanine is green tea which you know I love! Green tea is high in L-theanine which is a natural substance that is gaining a lot of attention for its potential health benefits. If you aren’t a green tea lover hopefully you will be converted after reading this article written by my intern, holistic nutritionist Robyn.

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. This gives it the ability to exert potent effects on the brain and nervous system. L-Theanine has amazing benefits including reducing mental and physical stress, improving cognition, and boosting mood. If you’re looking to feel relaxed without drowsiness, a cup of green tea might be just what you need.

Health Benefits of L-theanine

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.

Boost relaxation and reduce the effects of stress

The majority of research on 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 a deep state of mediation. In one randomized, triple-blind crossover study, healthy participants were given either 200mg of L-theanine or placebo. They gave everyone a mental arithmetic test before and after the dose to stress them out. 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. 

Bolsters cognitive functioning

L-theanine helps you enter into a relaxed mental state and also helps boost cognitive function 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.

Supports working memory

Glutamate is an excitatory neurotransmitter that shapes learning and memory. However, excess glutamate can cause neuronal death and impair memory processes. 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 a 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, “Brain 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 the 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.

Provides mood support

One of the most well-known health benefits of L-theanine comes 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.

May help improve sleep quality

Having a hard time catching some “Zzzs”? 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?

Green tea and other teas

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 or with the addition of milk or sugar. Most people can enjoy green tea and reap the health benefits of L-theanine.

Coconut Banana Matcha Chia Pudding Recipe by Jesse Lane Lee

Recipes to experience the health benefits of green tea


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.

Wakeup Matcha Green Smoothie by Jesse Lane Wellness

Meet Robyn, the author of The Health Benefits of Green Tea

A registered nurse (RN) by trade, Robyn merges medicine with natural health to create a personalized health and wellness protocol that addresses the root cause of your persistent symptoms. The goal? To restore function to your body through unprocessed foods and targeted supplements to prevent and reverse disease. Say goodbye to band-aid solutions. Connect with Robyn on Instagram as @rn_nutritionist and check out her website Good Food Works for more.


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