L-theanine is an amino acid that is found in tea leaves. It was identified in tea by Japanese scientists in 1949. While tea is the most common dietary source for L-theanine, this compound is also found in some types of mushrooms. In foods, particularly green tea, L-theanine is thought to be a source of umami, the savory, brothy taste.

Scientists studying umami flavor have made some interesting discoveries. Umami has been linked to decreased risk for obesity. It may stimulate metabolism, and may boost sensations of fullness and lengthen the time before hunger returns after eating.

There’s also evidence suggesting that L-theanine, when consumed in tea, may change taste perception, specifically diminishing the taste of bitterness in foods such as chocolate and grapefruit.

How L-theanine works 
L-theanine promotes relaxation and facilitates sleep by contributing to a number of changes in the brain:

Boosts levels of GABA and other calming brain chemicals. L-theanine elevates levels of GABA, as well as serotonin and dopamine. These chemicals are known as neurotransmitters, and they work in the brain to regulate emotions, mood, concentration, alertness, and sleep, as well as appetite, energy, and other cognitive skills. Increasing levels of these calming brain chemicals promotes relaxation and can help with sleep.

Lowers levels of “excitatory” brain chemicals. At the same time it is increasing chemicals that promote feelings of calm, L-theanine also reduces levels of chemicals in the brain that are linked to stress and anxiety. This may also be a way that L-theanine can protect brain cells against stress and age-related damage.

Enhances alpha brain waves. Alpha brain waves are associated with a state of “wakeful relaxation.” That’s the state of mind you experience when meditating, being creative, or letting your mind wander in daydreaming. Alpha waves are also present during REM sleep. L-theanine appears to trigger the release of alpha-waves, which enhances relaxation, focus, and creativity.

One of the appealing aspects of L-theanine is that it works to relax without sedating. That can make L-theanine a good choice for people who are looking to enhance their “wakeful relaxation,” without worrying about becoming sleepy and fatigued during the day.

Benefits of L-theanine

Improving sleep
With its ability to increase relaxation and lower stress, L-theanine can help in sleep in a number of ways. L-theanine may help people fall asleep more quickly and easily at bedtime, thanks to the relaxation boost it delivers. Research also shows L-theanine can improve the quality of sleep—not by acting as a sedative, but by lowering anxiety and promoting relaxation.

There’s evidence that L-theanine may help improve sleep quality in children with attention deficit hyperactivity disorder (ADHD). A study examined the effects on the sleep of boys ages 8-12, and found that the supplement worked safely and effectively to improve the quality of their sleep, helping them to sleep more soundly.

Reducing stress and anxiety
L-theanine is what’s known as an anxiolytic—it works to reduce anxiety. Some anxiolytics, such as valerian and hops, have sedative effects. L-theanine, on the other hand, promotes relaxation and stress reduction without sedating. L-theanine can help foster a state of calm, attentive wakefulness.

L-theanine has positive effects on both the mental and physical symptoms of stress, including lowering heart rate and blood pressure.

Research suggests that L-theanine can help reduce anxiety in people with schizophrenia and schizoaffective disorder.

Enhancing attention, focus, memory and learning
Under stress, the body increases production of certain hormones, including cortisol and corticosterone. These hormone changes inhibit some brain activity, including memory formation and spatial learning. L-theanine helps to lower levels of the stress hormone corticosterone, and avoid the interference with memory and learning.

L-theanine may help boost other cognitive skills. Research shows L-theanine can increase attention span and reaction time in people who are prone to anxiety. It may help improve accuracy—one study shows that taking L-theanine reduced the number of errors made in a test of attention.

Sometimes, L-theanine is used with caffeine to enhance cognitive skills. Studies show that combinations of L-theanine and caffeine can improve attention span, enhance the ability to process visual information, and increase accuracy when switching from one task to another.

Helping maintain a healthy weight
The anti-anxiety and sleep-promoting abilities of L-theanine may help people to maintain a healthy weight. After all, getting enough sleep and limiting stress are both key to sticking with a healthy diet and avoiding weight gain.

L-theanine may also play a more direct role in weight maintenance. There’s scientific evidence indicating L-theanine may help to limit fat accumulation and weight gain, and pay help to protect against obesity.

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