L-theanine to Boost Your Mood, Reduce Anxiety, and Help You Sleep

Among its health benefits, L-theanine increases alpha brain waves that occur when we are relaxed.
L-theanine to Boost Your Mood, Reduce Anxiety, and Help You Sleep
(Pheelings media/Shutterstock)
Emma Suttie

Many of us already know the therapeutic effects of a good cup of tea, and science is starting to discover how those effects come about.

Tea leaves contain an amino acid called L-theanine, which imbues tea with its unique, umami flavor. L-theanine is a bioactive compound that also boasts an impressive list of health benefits, including antioxidant, anti-inflammatory, neuroprotective, and anticancer effects. It can also protect the heart, liver, and kidneys, regulate the metabolism and support the immune system, according to an research review published in Frontiers in Nutrition.

Tea (Camellia sinensis) originated in China and is one of the most popular beverages in the world. The way that tea leaves are processed, such as fermentation and baking, can change the color, smell, taste, and compounds of the tea.

Tea normally falls into six categories depending on the level of fermentation that tea leaves go through—yellow, green, white, black, oolong, and dark tea.

There is also matcha tea, in which typically younger leaves are ground up and drank in their entirety, but we'll be focusing on it in another article.

Each type has its own unique flavor, aroma, and health benefits. Even though the amount varies, all teas made from the Camellia sinensis plant contain L-theanine. Green tea, however, is its most abundant natural source.
All teas from the Camelia sinensis plant contain L-theanine, although to varying degrees. (Miss Nuchwara Tongrit/Shutterstock)
All teas from the Camelia sinensis plant contain L-theanine, although to varying degrees. (Miss Nuchwara Tongrit/Shutterstock)
Caffeine and L-theanine have a synergistic relationship, and in combination, have a unique effect on the brain with research showing that they can improve mood and cognition.
L-theanine is also known as theanine, 5-N-Ethyl-Glutamine, and gamma-glutamylethylamide.

Reduces Anxiety and Stress

We could all probably use a natural way to help us manage anxiety and stress. Although these are natural responses to certain situations, when they are prolonged, or experienced at intense levels, they take a toll on us—physically and psychologically. After a long day, one of the best things you can do is curl up and enjoy your favorite cup of tea to gain the calming effects of L-theanine.
According to the latest federal data, 32.3 percent of adults reported symptoms of anxiety or depression in 2023, and that number is even higher—49.9 percent—in those aged 18–24.
A systematic review found that L-theanine in the form of green tea helped to manage stress and anxiety levels in people exposed to stressful conditions. The findings suggest that supplementation with between 200–400 milligrams (mg) of L-theanine daily assists in the reduction of stress and anxiety.
A randomized controlled trial published in Nutrients examined the effects of four weeks of L-theanine supplementation on stress-related symptoms and cognitive function in healthy adults. Researchers concluded that L-theanine may promote mental health in people with stress and other cognitive impairments.
In another randomized controlled trial on fifth-year university students about to enter their pharmacy practice, researchers wanted to determine if theanine had an effect on the students and their levels of stress.
The students were split into two groups—both were to receive 200 mg of theanine or a placebo, twice a day. The interventions (either theanine or placebo) were taken a week prior to students entering their pharmacy practice and continued for ten days into the practice period. The student’s anxiety was assessed using an anxiety test (the State Trait Anxiety Inventory) and a saliva test that measured sympathetic nervous system activity (stress). The researchers found that subjective stress was significantly lower in the theanine group than in the placebo group.

Increased Alpha Brain Waves

Human electroencephalograph studies show that L-theanine has a direct effect on the brain and that it significantly increases alpha brain waves, which is an indication that it relaxes the brain without causing drowsiness. However, one study notes that this effect is only achieved at doses higher than can be acquired from a cup of black tea (approximately 20 mg).
L-theanine has been shown to directly increase alpha brain waves which have been shown to reduce depression and anxiety. (peterschreiber.media/Shutterstock)
L-theanine has been shown to directly increase alpha brain waves which have been shown to reduce depression and anxiety. (peterschreiber.media/Shutterstock)
Alpha brain waves are one of five types of brain waves which include delta, theta, beta, and gamma waves. Each type of brain wave is associated with different frequencies and occur when people are in different states. Alpha brain waves occur when we are relaxed and usually arise when people are engaged in activities like daydreaming, meditating, or practicing mindfulness. Research has shown that alpha waves have a number of positive benefits which include reducing depression, increased creativity, and reducing anxiety.
Another study, titled “200 mg of Zen: L-Theanine Boosts Alpha Waves, Promotes Alert Relaxation,” states that research with human volunteers has shown that L-theanine creates a sense of relaxation 30–40 minutes after consuming it and that it achieves this effect because L-theanine stimulates the production of alpha brain waves directly, creating a state of deep relaxation and mental alertness that is often achieved through meditation.

Helps You Sleep

As a culture, we suffer from a chronic lack of adequate sleep, and as any insomniac (or new parent) can tell you, not getting enough good quality sleep negatively affects every aspect of life—from energy levels to the ability to think clearly. Chronic sleep deprivation is also associated with an elevated risk of chronic diseases like depression, heart disease, diabetes, and obesity.

Because we can’t always control the factors in our lives that affect how well or how much we sleep, having some natural remedies on hand is a good idea to help us catch some of those elusive z’s.

While most medications used to induce sleep are sedatives—often associated with addiction and other side effects—L-theanine is unique as it is not a sedative and promotes good quality sleep through a process called anxiolysis, or the reduction of anxiety. L-theanine also promotes relaxation without drowsiness.
In a randomized controlled trial, objective sleep quality was tested using L-theanine in a group of boys with attention deficit hyperactivity disorder. Ninety-eight boys aged 8–12 were split into two groups, one group receiving 400 mg of L-theanine and the other a placebo for six weeks. The study found that the boys who received L-theanine had significant improvement in sleep scores compared to those in the placebo group.
Of course, taking L-theanine in the form of tea would also include caffeine, which will counteract any sleep-inducing effects.

L-theanine and Cancer

L-theanine has also been shown to be beneficial against cancer. Research has shown that L-theanine is able to increase the antitumor activity of some drugs used in chemotherapy.
In one study using mice, theanine was used to enhance the activity of the chemotherapeutic drug doxorubicin on ovarian cancer that had metastasized to the liver. The study found that theanine not only increased the antitumor activity on primary tumors but also the metastasis-suppressive effectiveness of the drug doxorubicin.
In another mouse study, theanine was found to increase the antitumor activities of the chemotherapy drug idarubicin, while simultaneously decreasing its toxicity.

Dosage and Toxicity

L-theanine is usually taken in doses of between 100–200 mg a day. It is often taken with caffeine but doesn’t have to be to reap its healing benefits. Its calming effects can usually be felt within 30–60 minutes after taking it.
L-theanine also has very low toxicity. In fact, a rodent study using L-theanine failed to find any toxic effects using 4000 mg of L-theanine per kilogram of body weight when used daily for 13 weeks. Other animal studies have shown similar results with no detected toxicity even when using L-theanine at very high doses. L-theanine also seems to be safe to use in humans, with no known toxicity or adverse effects reported. L-theanine does have blood pressure-reducing abilities, so it is recommended that if you are on blood pressure medications to consult with a health care practitioner before taking L-theanine supplements or significantly increasing your consumption of green tea.

Final Thoughts

As our lives become more and more complex, finding ways to help us stay grounded, manage stress, remain focused, and get more good quality sleep is a welcome addition to our hectic, modern-day lifestyles. With challenges like depression and anxiety on the rise, medications may not always be necessary—the solution may be as simple as curling up with a good cup of tea.
Emma is an acupuncture physician and has written extensively about health for multiple publications over the past decade. She is now a health reporter for The Epoch Times, covering Eastern medicine, nutrition, trauma, and lifestyle medicine.
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