This article first appeared on Dr. Axe.

What is L-theanine, and what is it used for? L-theanine (also called theanine, or sometimes r-glutamylethylamide) is an amino acid that impacts nerve impulses in the brain and the release of neurotransmitters, including GABA.

It is known as natural ananxiolytic because it can have a calming, sedative effect on the body and mind without making you feel drowsy — which is why it’s often used to reduce anxiety, hyperactivity and sleep-related problems.

Most people don’t acquire a lot of theanine from their diets since it’s not available in many commonly eaten foods. It’s a unique amino acid because it’s not used to form proteins — unlike many other amino acids, such as l-carnitine, leucine, lysine, methionine or tryptophan — and is not used to make enzymes. The greatest sources of L-theanine in our diets are green, black and white teas — but because most people don’t drink very large quantities of tea on a daily basis, L-theanine supplements can be beneficial.

As we’ll cover more below, drinking tea and taking L-theanine supplements can help reduce the effects of stress, protect the brain, support the cardiovascular system and much more.

What Is L-theanine?

L-theanine is considered a nondietary, nonessential amino acid because even though it has certain benefits, we don’t require it from our diets.

What does L-theanine do for you? It is used to help prevent and treat conditions, including:

  • Anxiety, depression and other mood-related disorders
  • Insomnia and trouble sleeping
  • Cognitive loss, dementia and Alzheimer’s disease
  • Stroke
  • High blood pressure and other cardiovascular problems
  • Post-traumatic stress disorder (PTSD)
  • Schizophrenia
  • Poor attention span
  • Substance dependence
  • It may help improve the effects of drugs used to treat cancer drugs

L-theanine and the amino acid glutamine are structurally similar but have different effects and benefits. Both can be supportive of overall mental health and energy levels, but theanine is more capable of acting as a natural stress-reliever. Glutamine is one of 20 naturally occurring amino acids in dietary protein and is the most abundant amino acid in the bloodstream, making up 30 percent to 35 percent of the amino acid nitrogen in your blood.

Glutamine is needed to produce the neurotransmitter called glutamate. Glutamate is considered an excitatory neurotransmitter, but L-theanine binds to the same receptors in the brain as glutamate and therefore has opposite, inhibitory effects.

Is L-theanine the same as caffeine? No — the two are different, although they are both found in beverages, including green tea. Because L-theanine tends to promote relaxation, while caffeine promotes alertness, the two have opposite but complementary effects. However, studies suggest that both L-theanine and caffeine can have beneficial effects on cognition and mood when used appropriately.

5 L-theanine Benefits

What are the benefits of L-theanine? Below are five ways it can benefit your sleep, mental health, cognition and more.

1. Can Help Relieve Anxiety and Reduce Effects of Stress

One of the most well-researched L-theanine benefits is its ability to promote relaxation and fight stress. It is said to be “a relaxing agent without causing sedation,” meaning it can help improve your ability to deal with stress without making you feel lethargic or tired.

If you suffer from nervousness, anxiety, depression or other stress-related issues, you can likely benefit from L-theanine’s relaxing effects, although it likely won’t have a strong enough effect to reduce severe anxiety. (3) In one study, L-theanine was shown to reduce scores on a tension-anxiety test compared to placebo. Both L-theanine and caffeine’s effects on mental task performance and physiological activities were investigated. Participants were placed under conditions of physical or psychological stress, in which they orally took either L-theanine + placebo, caffeine + placebo or placebo only. Results after the mental tasks showed that L-theanine significantly inhibited the blood-pressure increase associated with stress, while caffeine tended to have a similar but smaller inhibition of blood pressure.

What does L-theanine do to the brain to help calm you down? L-theanine has anti-stress effects because it inhibits (blocks) cortical neuron excitation. Theanine has been found to cross the blood-brain barrier, especially when given as an injection, and when taken orally it can increase brain concentrations of the compound for up to five hours. Theanine seems to impact two important areas of the brain called the amygdala and hippocampus, which help control fear responses and memory.

Theanine may also increase alpha brain waves (α-waves), which are associated with a state of “wakeful relaxation,” selective attention mechanisms, arousal and mental alertness. One study tested the effects of L-theanine on brain waves 45, 60, 75, 90 and 105 minutes after ingestion of 50 milligrams of L-theanine. The results showed that there was a greater increase in alpha activity across time in the L-theanine condition relative to placebo. According to the authors of the study, “These data indicate that L-theanine, at realistic dietary levels, has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention, and further research is therefore focussed on understanding the effect of L-theanine on attentional processes.”

2. May Help Improve Sleep and Fight Insomnia

Why is L-theanine good for sleep? Mostly because it helps reduce stress and anxiety, which can keep you up at night if you’re constantly worrying, tossing and turning. The effects that theanine has on sleep are mild, so it won’t work for every person to improve sleep quality. While it can have positive effects on sleep quality, it probably won’t be enough to help someone with moderate or severe insomnia to get a good night’s sleep.

Certain studies have found that L-theanine can help to improve sleep quality in people with conditions that cause hyperactivity, including ADHD. (7) Another positive attribute of L-theanine when it comes to sleep is that it can counter the effects of stimulants. This means that if you drink lots of coffee or use other stimulants for medical reasons, L-theanine’s calming effects may help reduce wakefulness, jitters, etc.

Some people choose to take L-theanine and melatonin together to help with sleep. A common dosage is around three grams of melatonin before bed taken with 100–200 milligrams of L-theanine. The two can act together to reduce stress and help with sleep quality, although L-theanine taken in high doses (above 600 milligrams) may have opposite effects.

3. May Help Improve Attention

Some people choose to use L-theanine and caffeine together in order to improve alertness, cognition and attention. The two have a “synergistic” relationship and can lead to improved focus without feeling overly “wired” or jittery. For this purpose, consuming about 200 milligrams each of L-theanine and caffeine tends to lead to the best results. (8)

4. Can Help Protect Memory and Cognition

In one double-blind, placebo-controlled study, patients with mild cognitive impairment were given 360 milligrams of green tea extract along with 60 milligrams of theanine (a combination called LGNC-07) three times daily for 16 weeks. Researchers found that LGNC-07 helped improve recognition skills without having any negative effects on verbal and visuospatial memory. (9)

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 three hours in the eye-open and reading states. Therefore, this study suggests that LGNC-07 has potential as an intervention for cognitive improvement.”

One way in which L-theanine may help to protect the brain is by preventing excessive glutamate stimulation of brain cells (excitotoxicity), which some believe is linked to neurodegenerative disorders, stroke and schizophrenia. By blocking some of glutamate’s effects, L-theanine may be able to offer neuroprotection for the aging brain.

5. May Help Support Cardiovascular Health 

Green tea is the top source of L-theanine, and many studies have found evidence that green tea can help reduce inflammation and support heart health. Some experts believe that green tea is protective of cardiovascular health mostly because it provides theanine, rather than due to other active compounds like green tea catechins or theaflavins.

Theanine may help to prevent blood pressure spikes in response to stressful events and help regulate nitric oxide. Nitric oxide is a molecule that our bodies produce to help cells communicate, regulate blood pressure by dilating arteries, reduce inflammation, support the immune system, improve sleep quality and more. The endothelium layer of our arteries produce nitric oxide, which helps relax narrowed blood vessels and increases oxygen and blood flow. Adequate production of nitric oxide can help to protect against artery-blocking clots or obstructions, heart attacks, stroke and other cardiovascular problems.

Some studies have also found that administration of L-theanine after a stroke, ideally within 12 hours but potentially up to 24 hours later, may help protect brain cells and reduce damage caused by the stroke. (10)

In studies conducted on roundworms (the species C. elagans), theanine supplementation has even been shown to help slightly increase life span and promote longevity. Roundworms that were exposed to L-theanine at high concentrations experienced an extended life span by an average value of 3.6 percent and up to 4.4 percent. (11) Researchers did not find that more theanine provided more benefits when it came longevity; a dosage on the lower end of the range was actually the most effective.

L-theanine Foods/Beverages

Is L-theanine natural? Yes, it’s found in certain foods and beverages, including green tea (made from the leaves of the camellia sinensis plant). Along with caffeine and catechins, L-theanine is one of the main active ingredients found in green tea. It’s believed that theanine actually gives green tea its slight umami flavor and helps counteract the bitter taste of green and black tea — and other bitter-tasting foods like cocoa.

How much L-theanine is in green tea? It comprises up to 50 percent of the total amino acids in tea. About at 0.9 percent to 3.1 percent of the dry weight of green tea leaves is theanine. This equates to about 25 to 60 milligrams of theanine per 200 milliliters of tea, or about 6.7 ounces. This amount of tea is typically made from about 2.5 grams of dried tea leaves. Theanine content in green tea varies depending on the specific type of tea. Teas made from younger plants have a higher theanine content than teas made from older plants. Theanine content is also reduced from fermentation (part of the process used to make tea leaves), but it becomes more concentrated when leaves are dried.

What other foods have L-theanine in them? L-theanine can also be found in leaves used to produce black and white teas, although most research has focused on theanine from green tea. Other plants that provide L-theanine include:

  • C. japonica and C. sasanqua — These are small shrubs that produce pink and red flowers. They are sometimes used make tea, although not as commonly ascamellia sinensis. (12)
  • The mushroom species called Xerocomus badius — Also called bay bolete, this is a brown, edible, pored mushroom found in Europe and North America. (13)

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