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 anxiolytic 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
- High blood pressure and other cardiovascular problems
- Post-traumatic stress disorder (PTSD)
- 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 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. It is considered an excitatory neurotransmitter, but L-theanine binds to the same receptors in the brain as glutamate and therefore has opposite, inhibitory effects.
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.
L-theanine was first identified in tea leaves by Japanese scientists in 1949. One of the reasons that scientists first started studying theanine was because it was believed to be a source of umami, which basically means a savory, brothy taste that is only found in certain foods, like meat, fish, mushrooms and some vegetables.
Researchers believe that umami flavor may actually affect the brain in a way that helps decrease the risk for obesity, stimulate the metabolism, alter taste perception of bitter foods, boost satiety and fullness, and hold off hunger and cravings between meals.
In Ayurvedic medicine, the best source of theanine, green tea, is considered valuable for its high antioxidant content, however the caffeine in green tea is not recommended for every body type. Because green tea contains low amounts of caffeine, it’s considered a better choice than coffee and other stimulants, especially for Vata and Pita types who may already deal with restlessness and anxiety.
Another reason that green tea is considered a healing beverage in Ayurveda is because it can help balance out the effects of stimulants and stress. This is beneficial for achieving doshic balance, especially when green tea is consumed with herbs and spices.
Because each type has unique properties, many tea varieties are included in the Ayurvedic diet, such as:
- Jasmine green tea, which can also have sedating effects on the nervous system.
- Moroccan mint green tea, which can help to soothe digestive issues and nausea.
- Bancha tea, an expensive tea that’s a good source of catechins.
- Ginger green tea, which supports the immune system and digestive system.
- Cinnamon green tea, which fights inflammation.
- Genmaicha tea, which is warming and energizing.
- Matcha tea, which contains concentrated levels of L-thianine.
Green tea has been consumed in China and other parts of Asia for thousands of years. According to Traditional Chinese Medicine (TCM), tea is the most beneficial of all herbs and has numerous benefits, including improving alertness, supporting immunity, balancing body fluid production, quenching thirst, clearing heat and phlegm, and promoting healthy digestion and urination.
In TCM, the amount of green tea that’s recommended depends on the condition being treated. An average of three cups of green tea (approximately 750 milliliters) per day is commonly recommended, however upward of 10 cups (2,500 milliliters) may be beneficial for treating certain health conditions.
While green tea is most valuable in TCM, many other types of teas are also encouraged, including white, black and oolong teas.
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.
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, examining the effects of L-theanine. 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.
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? 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 improve sleep quality in people with conditions that cause hyperactivity, including ADHD. 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 milligrams 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 — and so may melatonin.
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.
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.
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 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 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.
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.
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 vs. GABA
- L-theanine can help to stimulate production of the inhibitory, relaxing neurotransmitter called GABA (gamma-aminobutyric acid).
- GABA, like serotonin and dopamine, is known as a neurotransmitter. It helps regulate emotions, moods, concentration, motivation and alertness. GABA can also affect sleep, appetite and sex drive.
- GABA is known to have calming, anti-anxiety effects, making it beneficial for lifting your mood and preventing nervousness or hyperactivity. By increasing GABA, this is one way that L-theanine has calming effects. By elevating GABA, L-theanine may help reduce symptoms of depression, such as fatigue, changes in appetite, insomnia and lack of motivation.
- Some anti-anxiety medications work by mimicking the effects of GABA, but these are commonly associated with drowsiness. What makes L-theanine so attractive as a calming agent is that it doesn’t impair motor skills or make you feel tired. In fact, it can increase alertness and promote relaxation at the same time.
- Injections of theanine have been found to increase cerebral concentrations of GABA most, sometimes by up to 20 percent when given in high doses. Taking moderate doses of theanine is likely to have a mild effect on GABA levels, although it can be enough to cause a noticeable difference in your mood.
Risks and Side Effects
Is L-theanine safe? Research suggests that it is safest when used in the short term, for about several weeks to four months.
It is typically taken by mouth one time per day for about three to 16 weeks. It’s not clear if it is always safe or effective if taken for longer periods.
How much L-theanine is safe to take? Most people can safely take up to 200 milligrams daily (usually split into two to three doses), although higher doses around 400 milligrams have also been used safely.
L-theanine can interact with certain medications, including those taken to control high blood pressure (called antihypertensive drugs) and stimulants. Theanine can decrease blood pressure, so don’t supplement with it before speaking with your doctor if you already take medications that lower your blood pressure.
Examples of medications that lower blood pressure include aptopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan) and diltiazem (Cardizem).
Theanine will also interfere with the effects of stimulants (including both foods/drinks and medications), since it can slow down activity of the nervous system. If you any take stimulant drug, including diethylpropion (Tenuate), epinephrine, phentermine (Ionamin) or pseudoephedrine (Sudafed), then don’t take L-theanine without consulting with your doctor.
Although this may be a good thing, L-theanine can also decrease the stimulating effects of caffeine and certain herbs, including coffee, tea, green tea extract, guarana, yerba mate, cola and other caffeinated sodas, and energy drinks.
Because there hasn’t been much research done focusing on safety of L-theanine supplementation during pregnancy, it’s best for pregnant women to avoid taking L-theanine (although drinking one to two cups of green tea during pregnancy is considered safe for most women).
Dosage and Supplements
Because L-theanine is almost exclusively found in tea leaves, it can be hard to get enough from foods and drinks alone to notice its positive effects. This is why people turn L-theanine in supplement form.
Theanine supplements generally come in the form of L-theanine, which is the bioavailable supplement form of the amino acid theanine. Suntheanine is a theanine supplement made with a patented fermentation process. While manufacturers of suntheanine may claim that its more potent, there doesn’t seem to be much difference between the quality of L-theanine and suntheanine when it comes to efficacy and tolerance.
Where to Find and How to Use L-theanine:
Theanine supplements come in different forms, including capsules, pills and tablets. To ensure you’re buying a quality product, always check the ingredients in the supplement formula. Purchase a supplement that is pure theanine/L-theanine and does not have fillers or other chemicals.
Keep in mind that some energizing theanine formulas may include caffeine, which would not be beneficial to reducing anxiety or helping with sleep.
- L-theanine is typically taken in dosage of 100–200 milligrams per day. It can be taken along with caffeine but doesn’t need to be.
- The calming effects of L-theanine usually kick in within about 30–60 minutes after taking it.
- To help treat insomnia, ADHD and hyperactivity, doses of 200 milligrams taken twice daily are usually most effective.
- Higher doses of L-theanine, around 400 milligrams, may be used to help manage symptoms of schizophrenia or severe anxiety disorders. This dose may be used for up to eight weeks.
- For help with reducing anxiety, a combination of L-theanine (400 mg per day) and the hormone pregnenolone (50 mg per day) is sometimes used.
Can you take L-theanine on an empty stomach? Yes, L-theanine can be taken either with meals or on an empty stomach.
If you haven’t recently eaten when taking L-theanine, you may feel the effects a bit more quickly and intensely (similar to drinking caffeine with a meal versus on its own/on an empty stomach). If you’re using L-theanine to help you sleep, try taking it about 30–60 minutes before bed.
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 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 as camellia 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.
- L-theanine (or simply theanine) is a nondietary amino acid that is found in green, black and white teas, plus can be taken in supplement form.
- L-theanine has relaxing properties without making you feel drowsy. It can be used to make you feel calmer, improve attention span and focus, and support restful sleep. Not only is L-theanine calming and centering, but it can also help protect the heart and brain, plus help regulate blood pressure and reduce symptoms of schizophrenia.
- The best natural way to obtain L-theanine is to drink several cups of quality green tea and others teas every day.
- L-theanine is safe when taken in supplement form but will reduce effects of blood pressure medications and stimulants. The typical dosage is between 100–400 milligrams per day. Some people use low doses of L-theanine and caffeine together to improve focus without feeling jittery.