While browsing supplements to improve your health, you may have come across theanine and may find yourself wondering what is theanine? Theanine or L-Theanine is an amino acid that may improve cognitive functioning and reduce stress. If you’re anything like me, both of these sound helpful. I have a busy, stressful life, and reducing stress while improving my cognitive function would help me live a better life.

What is Theanine?

Theanine or L-Theanine is an amino acid commonly found in green tea. It can also be found in some mushrooms. Theanine is currently known to help with cognitive function and is being researched for many other benefits like lower stress and better sleep. It seems to work similarly to glutamate, which transmits nerve impulses in the brain. Theanine is responsible for the savory umami flavor in green tea. This is the brothy flavor commonly found in Asian cuisine.

Further research is still needed to determine what exactly theanine helps with as well as how it works in the body. Tea in general and green tea in particular shows many of the benefits of theanine, but it isn’t currently known just how much of the benefits of tea are from theanine itself rather than other substances in tea. Studies are still in progress and many show conflicting results. The European Food Safety Authority doesn’t recognize any health claims from theanine. However, it is generally considered safe by the FDA.

Germany currently doesn’t allow theanine to be added to drinks. This is because a safe or typical dose has not yet been decided. How much theanine is actually extracted during a typical brewing of green tea has not been researched yet either. In particular, the habit of Japanese tea drinkers to throw out the first extraction from green tea has not been researched to see if this affects how much theanine is actually consumed by the average Japanese tea drinker.


There are many benefits that are currently being researched. We will go over them briefly here.

Sleep and relaxation

This is one of the biggest uses studied currently. Tea has been used as a calming drink for centuries and what role theanine plays in this is a hot topic for research. Many studies go over whether theanine will affect sleep and if it can reduce stress. The results for this with a dosage of 200mg look quite promising.


Theanine combined with caffeine can improve alertness while still leaving you feeling calm. If you would like the stimulant effects of caffeine but you find it makes you jittery, theanine may help you out. Since tea naturally contains both caffeine and theanine, this may be why some report that they find tea a better way to caffeinate than coffee or energy drinks.

Anxiety reduction

Currently, studies are being done to see if the relaxing effects of theanine will also help with anxiety symptoms. Research is currently divided, but it can help improve sleep for those diagnosed with Generalized Anxiety Disorder.


The symptoms of depression were found to be reduced in an open-label study. This means that the results could be a placebo effect or be inflated by the said effect. Things like alertness improved and symptoms of anxiety were reduced. If you have a major depressive disorder, theanine may help reduce your symptoms when used in addition to your current medication and therapy. It has not been evaluated on its own though.

Increased focus

Thanks to increased sleep quality and reduced stress, cognitive function and focus were improved with theanine treatment. For the general population, theanine could improve health and mental performance.

Cancer treatment effectiveness

Theanine was found to improve the function of several cancer drugs used for treating non-small cell lung cancer in humans. It also helped by reducing the migration of these same cancer cells. This suggests that it could improve outcomes for patients with non-small cell lung cancer. It might also be effective in improving the results of anticancer drugs, but more research needs to be done. Be sure you follow the recommendations of your oncologist.

High blood pressure

High blood pressure can be lowered with theanine. This is particularly true for stressful activities that can raise blood pressure. Patients taking theanine had a less severe rise in blood pressure when in stressful situations.


This is one of the biggest uses for theanine. Stress responses can be lowered and things affected by stress like sleep can be improved. Many benefits noted for theanine come partly from this reduction in stress symptoms.

Cognitive function

Cognitive function has been noted as being improved by several metrics. Scores for a few cognitive tests were improved versus a placebo.

Relaxation without drowsiness

This is an important effect. While many things can help you relax, they may make you drowsy. Theanine can allow you to relax without falling asleep. This can be good for those dealing with stress at work. It can also help people who want to relax but still be able to get tasks done.

The wide range of effects means that you might see quite a few benefits by adding theanine to your diet. It’s very easy to get plenty of theanine even if you dislike taking supplements on their own and prefer adding to your diet.

Many benefits reported from drinking tea like stress-reduction may be caused by the theanine content. How much will cause this effect and whether theanine can achieve this as a separate supplement is still being studied. If you want to get some benefits of theanine by drinking tea, it is a good idea to look at studies surrounding tea drinking. The health effects of tea are much more well studied than theanine. You could also be getting the benefits of theanine if you increase your tea consumption.

Just remember that all effects are still under study and may be proven false or overstated in the future. Keep yourself in the know by watching out for any studies that analyze theanine and its effects on human health. Look out for studies on tea if you are drinking tea, and read about supplements if that is how you are taking it.

Sources of Theanine

Theanine is naturally found in all forms of tea from the tea plant. Green tea has the highest concentration, but it can be found in many varieties of tea. It can also be found in smaller amounts in bay bolete mushrooms and some other fungi. There are no other known sources that are rich in theanine. If you want it without drinking tea, you will need to get it from supplements. These are fairly common on the market by now, so they aren’t too difficult to source.

Any tea can help you get more theanine in your diet. You can pick any variety, though green teas will have the biggest concentration. Even cheap supermarket tea contains about 20mg of theanine in a cup. One thing to remember is that herbal teas will likely not have any significant amounts of theanine. This is because herbal teas aren’t made from leaves from the tea plant. Be sure you’re getting leaves from Camellia Sinensis. This means you are drinking true tea and not just an herbal infusion that will have different chemical compounds. Green tea grown in the shade like matcha has the largest theanine content.

One thing to remember is that most tea includes caffeine, and too much caffeine can have a negative effect on your health. Look for a decaffeinated tea if you want to add theanine without all the caffeine.

If you’d like to switch it up and get tea into your food, there are many ideas for this. Using tea instead of broth can be a fun idea. There are so many teas out there that you can easily find a flavor to complement any food. Just try to use liquid tea since water extracts most of the theanine from tea.

If you love drinking your tea but are getting tired of the standard flavors from brewing a simple cup, you can go for more enjoyable recipes with fruit and other ingredients. This article can give you some ideas on what beverages you can make with tea.

Eating foods that include tea leaves will also give you the effect, so tea cookies made with ground tea leaves will give you some of the benefits. Generally, green teas that grow in the shade like matcha have the most theanine so anything made with real matcha will have theanine in it in at least trace amounts.

Side Effects

Theanine has relatively few side effects that have been noted in studies. Most side effects are for things related to the relation effect like reduced alertness or sleepiness. It hasn’t been proven safe as a supplement for children or during pregnancy.

If consumed as a tea, the side effects are generally related to the natural caffeine content like irritability and digestive upset. If you drink tea already, a slight increase in consumption shouldn’t cause any harm. Otherwise, theanine tends to be well-tolerated in healthy adults so long as you stick with an appropriate dose.

Until more studies are done, proceed cautiously when using supplemented theanine. Make sure that you only make one change at a time so you can be sure what might be causing any changes to your health.


One thing to note when supplementing with theanine is that it can interact with certain classes of drugs. Since it can lower blood pressure, taking it with medication or supplements that lower blood pressure as well can lead to more severe drops that can be dangerous to your health.

It will also make stimulants like caffeine or pseudoephedrine (Sudafed) less effective. You should be sure to speak with your doctor or pharmacist if you intend on supplementing with theanine.

Always remember to discuss what supplements you take with your pharmacist since they can affect the dosage and delivery of your other supplements or prescription medication. Even more than a few cups of tea should be mentioned since tea is known to have many compounds that are extracted during brewing.


Because theanine is a supplement and not a drug, there are no official dosage instructions. Different studies have studied different dosages. It is likely hard to overdose on theanine supplements. The most common size on the market is 200 mg.

This study used a 50mg dose and then found an increase in alpha activity in the brain. This should increase mental alertness at this dose.

This study found that a 200mg dose increased verbal and letter fluency. They also found fewer sleep disturbances and less need for sleep medication in the same study.

It is recommended not to take more than 1200mg daily since the effects of large doses are still unknown. There are no studies that show how much theanine is consumed by your average tea drinker.


Theanine can be a good addition to your diet and supplement plan if you’d like more alertness without making yourself jittery. It’s best to get it by drinking tea since supplements on their own haven’t been thoroughly studied for safety in the long term. However, in my opinion, an excuse to drink more tea is never a bad idea.

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