- L-Theanine: Benefits, Dosage, and Side Effects | H.V.M.N. Blog
- L-Theanine: The Past and Present
- L-Theanine: The Benefits
- Reduces Anxiety and Stress
- May Help with Sleep
- Can Improve Focus, Memory, and Attention
- Powerful Antioxidant Properties
- Generally Safe
- May Interact with Other Medications
- L-Theanine: The Dosing
- Synergy with Caffeine
- The Future of L-Theanine
- 8 L-Theanine Benefits + Dosage, Side Effects
- What Is L-Theanine?
- Natural Sources of L-Theanine
- How Does L-Theanine Work?
- Benefits of L-Theanine
- 1) Brain Function
- Combination with Caffeine
- 2) Boosting Immunity
- 3) Anxiety and Stress
- 4) Sleep Quality
- 1) Schizophrenia
- 2) Preventing Heart Disease
- 3) Depression
- 4) Adjunctive Cancer Treatment
- Animal and Cell Research (Lack of Evidence)
- Weight Loss
- Stomach Ulcers
- Side Effects
- L-theanine: Benefits, risks, sources, and dosage
- 1. Better mental focus
- 2. Improved sleep
- 3. Relaxation
- 4. Increased cognitive performance
- 5. Weight loss
- 6. Boosting the immune system
- 7. Reducing blood pressure
- 8. Supporting certain cancer drugs
- What You Need to Know About L-theanine
L-Theanine: Benefits, Dosage, and Side Effects | H.V.M.N. Blog
Everyone is curious about what the future has in store for them. The difference is what we choose to do with that curiosity.
People attempt to find those answers from many sources, spiritual leaders and palm reading. Sometimes, they even go looking at the bottom of a cup of tea—tasseography is the ancient practice of reading and interpreting the formations of tea leaves at the bottom of the cup.
But you may not need to get to the bottom of your cup to get to the bottom of what’s to come from drinking it. So, what's in that tea? L-theanine, an umami-rich amino acid found in green tea and black tea leaves.
We’ll leave tasseography to the pros and tell you what the future holds in terms of L-theanine’s benefits, dosing variations, and possible side effects.
L-Theanine: The Past and Present
To discuss the future, we have to start with the past. L-theanine’s past is rich, owing to its tea drinker origins.
While the first credible documentation of drinking tea is as recent as 300 AD, the first teatime probably occurred in the Yunnan province of China during the Shang Dynasty thousands of years ago. If you believe one popular legend, tea wasn’t discovered on purpose.
King Shennong had simply boiled water to make it safe to drink when a gust of wind landed tea leaves from the nearby trees into his drink.1 He loved the taste.
King Shennong was also renowned for his willingness to experiment with various herbs and plants to see what effects they would have on him.
Lore says his body was translucent so that he could see what was happening on the inside.
1 For those of us who aren’t lucky enough (or unlucky enough) to see exactly what’s happening, there’s plenty of research surrounding the effects of tea on our bodies.
L-theanine was first isolated from the gyokuro leaf in a laboratory in Kyoto, Japan in 1949. Gyokuro is a type of green tea with a high L-theanine content, though the amino acid can be found in other green, black, and white teas from Camellia sinensis.2
L-theanine is a non-protein and non-dietary amino acid with a chemical structure and blood-brain barrier crossing similar to major neurotransmitters glutamic acid and gamma-aminobutyric acid (GABA).3 these neurotransmitters, L-theanine is heavily associated with the effects it can have on our moods.
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L-Theanine: The Benefits
From a research standpoint, L-theanine’s future appears bright. This amino acid has a laundry list of health benefits for both the body and brain.
Reduces Anxiety and Stress
If “busy” is a common response you give when someone asks how you’re doing, you may want to add L-theanine to your future for its most acknowledged advantage: the anxiolytic effect. Translation? It may be able to reduce your stress and anxiety symptoms.
In human studies, L-theanine has been linked to anti-anxiety effects possibly through inhibition of cortical neuron excitation.4 Unfortunately, excitation of your neurons doesn’t always result in feeling particularly excited. It's more a stimulant, so you may feel physiological and psychological stresses instead.
Our brains are always balancing this activity through the regulation of different types of neurotransmitters (e.g. dopamine, GABA, serotonin), generally categorized by their excitatory and inhibitory effects. But the system isn’t always perfect. The scales can tip in either direction, which can throw things off balance.
When you have an excess of the excitatory neurotransmitters, you may experience stress and/or anxiety.
You may also accidentally activate your sympathetic nervous system, more commonly referred to as the fight-or-flight response.
While the fight or flight response could save your life in a quick-thinking situation, such as a bear attack, it can be a problem when you activate it without really needing it.
At best, it may be a sweaty-palmed nuisance for its acute effects.
At worst, you may suffer from chronic stress and its accompanying physiological responses, an increased heart rate and spike in blood pressure, or an impaired immune system.5
The trigger for physiological stress responses is a release of the stress hormone, cortisol, from your adrenal glands. When L-theanine inhibits excitatory responses in the brain, the body’s regular responses will also be inhibited. Heart rate,6 blood pressure, and even salivary stress markers may all decrease with the help of L-theanine.4
May Help with Sleep
If sleeping is one of the ways you prepare yourself for the future, you may think you need a stronger supplement to help you wind down completely. L-theanine may be the perfect one to tuck you in.
Research shows L-theanine has the ability to generate alpha brain waves, which are typically generated during relaxing activities such as meditation.7 When the brain generates alpha waves in the parietal and occipital regions of the brain, you can experience a prolonged calming effect.8
Maybe, in your calm and drowsy state, you accidentally poured yourself a late afternoon cup of coffee from the regular pot rather than the decaf. Don’t worry—L-theanine can help ameliorate the effects of the late-night stimulus.
9 Caffeine isn’t just a barrier for your initial drift-off; it’s also a barrier to an adequate amount of slow-wave sleep (SWS), the deepest form of non-REM sleep.
In animal studies, L-theanine significantly reversed caffeine’s reductions of slow-wave sleep.9
Human studies have yielded promising results as well. A 2015 study on L-theanine’s sleep benefits, those with schizophrenia found significant improvements in sleep quality.
The results suggest that L-theanine’s therapeutic effect is owed to its stabilization of the glutamatergic concentrations in the brain.10 Glutamate is a fellow amino acid.
But it’s also one of the major excitatory neurotransmitters playing a significant role in schizophrenia.11
In a clinical trial, L-theanine also helped young individuals with attention deficit hyperactivity disorder (ADHD) with their sleep.
12 Sleep problems are common among individuals with ADHD, and sleep disturbances are equally common in the treatment of the disorder. L-theanine was tested for its safety and efficacy as a sleep aid.
The amino acid passed: participants not only fell asleep faster but also experienced higher quality deep sleep after supplementing with L-theanine.12
Can Improve Focus, Memory, and Attention
Maybe sleep isn’t your focus area for improvement; maybe focus is your focus area. If so, surrendering your attention to L-theanine may help it.
Human studies have shown L-theanine can increase focus, reaction times,13 and even visual processing, particularly in conjunction with caffeine.14
When supplementing with L-theanine, participants improved attention task performances for well-rounded cognitive function. But the participants didn’t just perform better; they felt better.
“Better” meaning reductions in self-assessed mental fatigue and increases in alertness.13
Let’s not forget what L-theanine can do for your memory. Consuming L-theanine over time gives it a chance to help protect the neurons in your brain from injury and death.
15 For those with Alzheimer’s disease, this benefit is huge.
In a 2009 mouse model studying a pathological mechanism of Alzheimer’s, L-theanine was found to attenuate its cognitive dysfunction through a reduction of associated oxidative damage.16
Powerful Antioxidant Properties
We utilize antioxidants to remove an excess of cell-damaging free radicals from our bodies. When our cells and tissues are damaged, it contributes to a host of larger issues and accelerates the arrival of diseases such as heart disease, cancer, and diabetes.
L-theanine’s ability to protect brain cells against oxidative damage contributes to its lengthening certification as an antioxidant. In addition to boosting the production of an infection-fighting antibody,17 L-theanine has been shown to provide direct neuroprotection against neurotoxicants.18
If you’ve taken sleeping pills before, you know they can get you to bed easily. But getting it the next morning? Nearly impossible. The negative side effects of these and other medications may have you making pros and cons lists.
While L-theanine isn’t completely without consequences, your “cons” list won’t be longer than the aforementioned benefits.
In essence, taking L-theanine is generally considered safe. It hasn’t been linked with any severe adverse effects. But let’s examine the word “adverse” more closely to understand what this description means.
Adverse means “causing harm.” If a medication or supplement “causes harm,” it will be noted. One step further, a “severe adverse” reaction is defined as anything that could be life-threatening, resulting in death, or resulting in a persistent or significant disability.19 Think liver failure, serious allergic reactions, and abnormal heart rhythms.
L-theanine has also been tested for its toxicity at extremely high levels.20
The results? L-theanine was still tolerated well after two weeks of supplementing with doses nearly sixty times the usual amount used in animal and human studies.
You won’t know the effects of L-theanine until you take it yourself. But numerous clinical trials and research findings have given us a sense of what you should be prepared to experience.
The most common side effects of L-theanine dosage include headaches, nausea, and irritability.21 However, the nausea appears to be mostly linked with L-theanine being administered through green tea rather than dietary supplements.
Similarly, the irritability side effect accompanies the dual administration of caffeine and L-theanine.
Even though L-theanine can increase focus and attention, you may be shy to use it because you’re worried its bedtime benefits will kick in during the day.
Luckily, L-theanine is not associated with sedative side effects, despite the stress reduction. L-theanine can generate alpha brain waves associated with relaxation, but these waves will not induce drowsiness.7
May Interact with Other Medications
Because L-theanine doesn’t induce daytime drowsiness in its relaxing effects, you won’t have to worry about it slowing you down. But it may slow your body down without you realizing it.
Remember that L-theanine supplements are able to reduce cortisol levels to inhibit your physiological stress responses. Even if they’re not the target of your L-theanine dose, you should always bear these effects in mind, especially if you’re taking L-theanine in tandem with other medications and supplements.
The dynamic duo: heart rate and blood pressure. L-theanine reduces both, particularly if an individual has high blood pressure.22 However, if you’re already on blood pressure medications, be aware that the effects could be either ameliorated or intensified through the introduction of the amino acid.
You should always discuss possible medication and supplement pairings with your healthcare provider before you try them.
L-Theanine: The Dosing
If you are ready to talk to your doctor about adding L-theanine to your daily (or nightly) routine, you’ll want to talk about the appropriate dose.
Remember that L-theanine is generally considered safe, even in high doses. The extremely high levels were around 4000mg – 6500mg each day. But just because L-theanine didn’t induce toxicity at extremely high levels doesn’t mean you should take exorbitant amounts of this amino acid to achieve the ultimate calm or increase your cognitive performance.
There is no current recommended dosage of L-theanine set by the Food and Drug Administration (FDA). However, clinical trials tend to administer the supplements between 100mg – 250mg.23 That’s about ten times higher than what you’ll find in a single cup of green tea.23 Save yourself the future stomach ache of ingesting that much tea and dose accordingly.
Synergy with Caffeine
If you’re looking to get an extra boost from your L-theanine without upping the milligrams, you may want to try pairing it with classic caffeine.
When taken together, the combination of L-theanine and caffeine can have a synergistic effect: increased reaction times,13 improvements in acute attention,24 and task switching.25 Further, because L-theanine is linked to better cerebral blood flow, it can reduce caffeine intake headaches.
The key to their success is proper dosing. If the balance is off, the effects may not be as noticeable. If you’re looking for the improved alertness without the jittery headaches, you should supplement every 150mg caffeine with about 250mg of L-theanine.13
The Future of L-Theanine
Even if you weren’t blessed with the ability to translate the tea leaf traces swirling around your cup, you may be able to exert better control over your own future by supplementing with one of the leaves’ core components.
Your future with the appropriate daily dose of L-theanine could mean less anxiety and stress, better quality sleep, a protective effect on your cells, and an attention boost in the mornings to get you going. And we predict you’re going to love it.
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8 L-Theanine Benefits + Dosage, Side Effects
L-theanine is an amino acid commonly found in tea. Together with caffeine, it may produce a distinct cognitive enhancement profile without the jitters or other side effects. In addition, L-theanine has many other potential health benefits. Read this post to learn more about the health benefits of theanine.
What Is L-Theanine?
L-theanine is an amino acid mostly found in tea leaves and fungi and used to help improve mood and lower stress, and to protect the brain and heart [1, 2].
Theanine usually refers to L-theanine, which has more potential health benefits compared to d-theanine.
Natural Sources of L-Theanine
- Tea (especially green tea) [2, 3]
- Bay bolete mushroom 
How Does L-Theanine Work?
L-theanine is able to cross the blood-brain barrier and affect the brain directly. In the brain, it may target brain chemicals that regulate arousal, anxiety, pleasure, and attention .
L-theanine increases brainserotonin anddopamine levels, which may improve memory and learning. It also increases the levels and effectiveness of GABA, the body’s main inhibitory neurotransmitter, and stimulates alpha brain wave activity, which may cause mental relaxation, concentration, and deep REM sleep [6, 7, 8, 9, 10, 11].
L-theanine may also increase glutathione levels, the body’s most important antioxidant molecule .
Given its similarity with the neurotransmitter glutamate, L-theanine may exert its neuroprotective effects by interfering with its function .
Benefits of L-Theanine
There are several L-theanine supplements commercially available, especially to curb anxiety, improve cognitive function, and boost immunity.
However, the FDA hasn’t approved them for any conditions due to the lack of solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective.
Speak with your doctor before supplementing with L-theanine.
1) Brain Function
In a clinical trial on 30 healthy people, L-theanine improved verbal fluency and executive function. In 18 healthy people prone to anxiety, L-theanine improved attention [13, 14].
In a clinical trial on 46 people with minor brain damage, a combination of L-theanine and green tea extract improved memory during a mental exercise. The combination improved recognition memory, attention span, and alertness during a memory test .
L-theanine also improved recognition memory in rats, possibly by promoting brain development [16, 17].
A breakfast bar with L-theanine, caffeine, L-tyrosine, alpha-linolenic acid, vitamins and minerals improved alertness, attention, working and episodic memory, and executive function in a clinical trial on 95 people .
L-theanine protected the brain against age-related cognitive decline in 29 elderly people and against brain damage due to aging, stress, and Alzheimer’s disease in animal studies [19, 20, 21, 22, 23].
Combination with Caffeine
L-theanine and caffeine are typically found together in tea. L-theanine often enhances the cognitive improvement effects of caffeine while reducing its negative effects (such as increased blood pressure) [24, 25].
In 5 trials on 124 healthy people, this combination improved sustained and target-specific attention, attention switching, reaction time, numeric working memory, and alertness better than either substance alone [26, 27, 28, 24, 29].
This combination also reduced the damage caused by restored blood flow after a stroke (ischemia-reperfusion injury) in rats .
Taken together, there is some limited evidence to suggests that L-theanine may improve brain function, especially attention and memory. You may consult with your doctor if it may be helpful in your case.
2) Boosting Immunity
High cortisol caused by intense exercise shifts the Th1/Th2 balance towards Th2. This increases white blood cells (neutrophils) while decreasing immune cells (lymphocytes), which leads to inflammation and immunosuppression. L-theanine (both alone and combined with L-cystine) reverted these effects in 4 clinical trials on 66 athletes exposed to strenuous exercise [31, 32, 33, 34].
L-theanine, both alone and combined with L-cystine, strengthened the immune system and reduced the incidence of the flu and common cold in 3 clinical trials on 376 people. In another trial on 55 people, the combination improved the efficiency of the flu vaccination. Similarly, the combination increased antibiotic production and prevented the flu in mice [35, 36, 37, 38, 39].
L-theanine boosted the activity of immune T cells, which protect against infections and cancer, in cell-based studies. It also maintained a correct Th1/Th2 balance towards Th1, which enhances resistance to infectious microbes, in rats [40, 41, 42].
Although promising, the evidence is still limited to conclude for certain that L-theanine boosts the immune system. You may take it for this purpose if your doctor considers that it may help.
3) Anxiety and Stress
In 3 clinical trials on 56 healthy people challenged with stressful situations, L-theanine reduced anxiety symptoms, along with heart rates and blood pressure. Similarly, both a theanine-based nutrient drink and low-caffeine green tea reduced stress responses and salivary stress markers (cortisol and alpha-amylase levels) in 2 trials on 54 people [43, 44, 13, 45, 46].
However, a study on 16 healthy people found that L-theanine was only relaxing under resting conditions, but not during acute stress episodes. In line with this, this amino acid didn’t improve anxiety symptoms in 46 people with a diagnosis of generalized anxiety disorder [47, 48].
Chronic L-theanine, as an add-on to their current medication, reduced anxiety, sleep disorders, and cognitive impairment in a trial on 20 people with major depressive disorder .
In 2 clinical trials on 100 patients with schizophrenia, adding L-theanine to their antipsychotic medication reduced anxiety and other symptoms [50, 51].
In rats, L-theanine reduced anxiety, suppressed the stimulatory effects of caffeine, and enhanced the anti-anxiety effects of the sedative midazolam [52, 53, 54].
All in all, L-theanine may reduce anxiety in healthy people challenged with moderate stress or those diagnosed with major depressive disorder or schizophrenia according to the existing evidence. Discuss with your doctor before using L-theanine to improve anxiety and never use it instead of what your doctor recommends or prescribes.
4) Sleep Quality
Green tea with high L-theanine and reduced caffeine content improved sleep quality and reduced stress in 3 clinical trials on 50 middle-aged and 10 elderly people [55, 13, 56].
L-theanine may also help with sleep disturbances caused by mental conditions. It improved sleep percentage and efficiency in 2 clinical trials on almost 100 boys with ADHD, 20 people with major depressive disorder, and 17 people with schizophrenia [57, 49, 58].
In mice, a mixture of L-theanine and the neurotransmitter GABA increased sleep duration and quality .
In rats, L-theanine partly counteracted the sleep disturbances induced by caffeine .
Again, limited evidence suggests that L-theanine may help with sleep disturbances, especially in people with anxiety. You may discuss with your doctor if this amino acid may help increase your sleep quality.
As an add-on to conventional medication for schizophrenia, L-theanine improved positive, negative, activation, and anxiety symptoms of this condition in 3 clinical trials on almost 100 people [61, 58, 51].
Because all 3 clinical trials were small, the evidence is insufficient to support the use of L-theanine in people with schizophrenia. Larger, more robust clinical trials are required to confirm these results.
2) Preventing Heart Disease
L-theanine prevented blood pressure increase caused by stress or caffeine intake in 2 clinical trials on 64 healthy people [44, 25].
L-theanine decreased blood pressure in hypertensive rats and lowered blood fat levels in obese mice [62, 63, 64].
L-theanine may lower blood pressure by increasing nitric oxide production, as seen in cell-based studies. Because it also prevented LDL oxidation, it might help prevent artery narrowing [65, 66, 67].
Again, the existing evidence is insufficient to conclude for certain that L-theanine may help prevent heart disease. Further clinical research is needed.
In a clinical trial on 20 people with major depressive disorder, L-theanine as an add-on to conventional medication helped with depressive symptoms, anxiety, sleep disturbances, and cognitive impairments .
L-theanine also depression caused by chronic stress, stroke, in mice and rats [22, 68, 69, 70].
A small clinical trial and some animal research cannot be considered conclusive evidence that L-theanine helps with depression. More clinical trials on larger populations are required.
4) Adjunctive Cancer Treatment
The oral administration of L-theanine together with L-cystine reduced the adverse effects of adjuvant chemotherapy in a clinical trial on 70 people with cancer in the stomach and bowels (gastrointestinal cancer) .
L-theanine also enhanced the anti-tumor effects of chemotherapeutic medication while protecting healthy tissues from these drugs in animal and cell-based studies [72, 73, 74, 75].
All in all, the evidence is insufficient to determine if L-theanine has any value in adjunctive anticancer therapy. Further clinical research is needed.
Animal and Cell Research (Lack of Evidence)
No clinical evidence supports the use of L-theanine for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed should not be interpreted as supportive of any health benefit.
The L-theanine in tea has dose-dependent antioxidant effects .
In multiple animal and cell-based studies, L-theanine protected the following organs from oxidative damage:
In mice, L-theanine, along with other components of green tea, reduced triglyceride and fatty acid levels in the blood, as well as food intake and body weight .
In a study in rats, L-theanine reduced the uptake of sugars and fats in the gut .
L-theanine healed stomach ulcers caused by an anti-inflammatory drug (indomethacin) in mice at a dose of 10 mg/kg body weight. It reduced oxidative damage and balanced the immune response. However, L-theanine aggravated ulcers at a 4x higher dose .
Because L-theanine is not approved by the FDA for any conditions, there is no official dose. Users and supplement manufacturers have established unofficial doses trial and error. Remember to consult with your doctor if L-theanine might be helpful in your case and what dose you should take.
For an average weight adult, L-theanine is usually available in pills of 50-200 mg. Some people take up to 600 mg a day.
For children, a smaller dose such as 25-50 mg, depending on their weight, is normally recommended.
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.
Call your doctor for medical advice about side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch
L-theanine: Benefits, risks, sources, and dosage
L-theanine is a compound that occurs naturally in green tea and black tea, and it is also available in supplement form.
Research suggests that L-theanine might provide a range of health benefits, which may include improved mental focus and better sleep quality.
This article provides an overview of L-theanine, including its potential benefits and risks and its dosage.
Share on PinterestL-theanine occurs naturally in black tea.
L-theanine is an amino acid. The human body does not produce this compound, and it is not essential for humans. Green tea, black tea, and certain types of mushroom naturally contain L-theanine.
L-theanine may affect the levels of certain chemicals in the brain. These include serotonin and dopamine, which influence mood, sleep, and emotion, and cortisol, which helps the body deal with stress.
A change in the balance of these chemicals can change a person’s mood or stress levels.
Small studies and tests on animals have shown that L-theanine may offer a range of benefits. Experts consider it to be generally safe, but there is currently a lack of high-quality research in humans to confirm its benefits.
The following sections discuss the existing evidence for the possible benefits of L-theanine.
1. Better mental focus
Many people drink black or green tea while at work, believing that it boosts their mental focus. A 2012 study supports this idea.
The researchers found that people who took 100 milligrams (mg) of L-theanine made fewer errors in an attention task than those in the placebo group. Drinking 50 mg of caffeine or combining the L-theanine and caffeine also improved people’s focus.
More research is necessary to determine how L-theanine might affect a person’s attention and focus.
2. Improved sleep
Share on PinterestL-theanine may help people sleep more easily.
Several studies have suggested that L-theanine could help people relax before bedtime, get to sleep more easily, and sleep more deeply.
These benefits may result from the specific effects that the amino acid has on brain chemicals that play a role in sleep.
A 2018 study found that people reported having greater sleep satisfaction after taking 450–900 mg of L-theanine daily for 8 weeks. The study participants had generalized anxiety disorder and were taking antidepressants.
The authors noted that there were no reported improvements in anxiety or insomnia severity.
People often drink a cup of tea or another hot beverage to help them relax. Research suggests that the L-theanine in green or black tea may contribute to this feeling of relaxation by reducing a person’s resting heart rate.
4. Increased cognitive performance
In 2016, researchers reviewed the existing research on the benefits of L-theanine and concluded that this compound could benefit a person’s mental and physical health. They noted that it seems to have neuroprotective effects, which improve brain function.
On its own, L-theanine may improve a person’s attention and reaction times. In combination with caffeine, it may lead to improvements in their number skills and alertness. Caffeine is a stimulant, so it can help people stay alert and focused.
However, not all research has found that L-theanine can improve people’s cognitive abilities. There is a need for more high-quality research to clarify the effects of this compound on people’s mental functions.
5. Weight loss
As part of a calorie-controlled diet, replacing a snack with green tea or another low-calorie hot beverage could aid weight loss.
The L-theanine in green tea can create a savory taste, also known as umami flavor. Research suggests that umami flavors may reduce appetite, which often helps with weight loss.
6. Boosting the immune system
L-theanine may support the body in fighting off illness. Several studies have suggested that taking L-theanine could boost a person’s immune system, making them less ly to get common colds or the flu.
Its potential anti-inflammatory effects could also help fight illness.
7. Reducing blood pressure
Research has linked high blood pressure with a higher risk of several health problems, including heart attack and stroke.
L-theanine may help reduce stress, and a reduction in stress and increased relaxation can lower the heart rate. In turn, this may help lower blood pressure.
8. Supporting certain cancer drugs
Some research on animals suggests that L-theanine may increase the effectiveness of a chemotherapy drug called doxorubicin. It is possible that it makes doxorubicin more effective by increasing the amount of the drug in cancer cells.
However, scientists need to do more research to understand the specific interactions between these chemicals.
While there is some evidence that L-theanine could benefit people’s mental and physical health, more studies are necessary before doctors can be sure of the actual effects of this compound. Scientists have not yet conducted high-quality research in humans.
Many studies to date have had a small sample size, meaning that very few people took part in the research. Data from just a small number of people are less ly to be conclusive than those from larger groups.
Other studies have used animals, such as rats or mice. However, humans are ly to react differently to animals, so these results may not be applicable.
After taking advice from experts, the FDA classified L-theanine as “generally recognized as safe.” This classification means that they believe this additive to be safe when people use it as the packaging suggests.
However, women who are pregnant or breastfeeding should not use L-theanine.
Most people are unly to experience side effects when they take L-theanine, but the supplement may interact with some medications.
It is essential to speak to a doctor about any current medications before taking L-theanine supplements.
L-theanine may interact with the following drugs and supplements:
- drugs for the treatment of high blood pressure
- other supplements that lower blood pressure
- stimulants, such as those that doctors use to treat attention deficit hyperactivity disorder (ADHD)
- supplements that contain caffeine
L-theanine is not a medication, so there are no official guidelines regarding how much a person should take. However, the supplement is unly to cause an overdose.
L-theanine is usually available in the form of 200-mg tablets. A person can consult a doctor before taking these supplements to get their advice on dosage.
Experts consider L-theanine to be generally safe for people to take as a supplement, but more research is necessary to confirm its possible health benefits. Small studies and research on animals suggest that L-theanine could help with relaxation, improved sleep quality, and neuroprotection.
What You Need to Know About L-theanine
I often encourage my patients to drink tea. Black tea is a lower-caffeine alternative to coffee during the day, and decaffeinated tea can be a calming part of a nighttime power-down ritual before bed. Whatever time of day or night, drinking a cup of tea can be a soothing, relaxing ritual. I often drink tea myself—my favorite is my personal recipe for banana tea.
In addition to its calming qualities, tea also contains compounds that deliver some real health benefits. One of those compounds: L-theanine.
Fortunately, you can also get L-theanine in supplement form, which can help with relaxation, focus, and sleep. Let’s take a closer look at L-theanine and its calming, centering, sleep-boosting abilities.
What is L-theanine?
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.
What to Know
Always consult your doctor before you begin taking a supplement or make any changes to your existing medication and supplement routine. This is not medical advice, but it is information you can use as a conversation-starter with your physician at your next appointment.
The following doses are amounts that have been investigated in scientific studies. In general, it is recommended that users begin with the smallest suggested dose, and gradually increase until it has an effect.
- For sleep, stress and other uses: 100 mg to 400 mg
- In combination with caffeine: 12-100 mg L-theanine, 30-100 mg caffeine
Possible Side Effects
L-theanine is generally well tolerated by healthy adults.
People in these groups should consult with a physician before using an L-theanine supplement:
- Pregnant women and those who are breastfeeding.
- Individuals with low blood pressure. L-theanine may lower blood pressure. If you have low blood pressure, speak with your doctor before beginning to use L-theanine.
- Children. Consult your child’s physician before beginning their use of L-theanine.
The following medications and other supplements may interact with L-theanine.
Effects may include increasing or decreasing sleepiness and drowsiness, interfering with the effectiveness of the medications or supplements, and interfering with the condition that is being treated by the medication or supplement.
These are lists of commonly used medications and supplements that have scientifically identified interactions with L-theanine. People who take these or any other medications and supplements should consult with a physician before beginning to use L-theanine.
Interactions with medications
- Medications used to treat high blood pressure
- Stimulant medications
Interactions with other supplements
Supplements that contain caffeine. L-theanine may interrupt the stimulating effects of caffeine and herbs or supplements that contain caffeine. Some of these include:
- Black tea
- Oolong tea
Supplements that lower blood pressure. L-theanine may lower blood pressure, and combining this supplement with other blood-pressure lowering supplements may cause blood pressure to drop too much. Some of these include:
- Casein peptides
- Cat’s claw
- Coenzyme Q-10
- Fish oil
- Stinging nettle
People have relied on the stress-relieving, sleep-promoting powers of L-theanine for centuries, by drinking tea—especially green tea. You don’t have to be a tea drinker to benefit from the soothing properties of this ancient herb—and even if you already enjoy a regular cup of tea, you may find an L-theanine supplement helps with relaxation, stress, and sleep.
Michael J. Breus, PhDThe Sleep Doctor™