L-Theanine: 4 Amazing Benefits, 3 Side Effects, & Dosage Details

April 27, 2022

There are many nutrients that can benefit your body and improve your health—and you're likely familiar with certain vitamins and minerals like zinc and vitamin C. But did you know that there are also amino acids that are essential to your well-being?

L-theanine is an amino acid often found in green tea and mushrooms that's known to promote relaxation and calm, boost mood, and even improve sleep

It’s so beneficial that I want to share more with you about this health-promoting amino acid, including where to get it and how to take it! So, keep reading to learn everything you need to know about what it is and how it can improve your health!


What is L-Theanine?

Amino acids are an essential part of any healthy diet. Together, they make up proteins that are responsible for several essential functions in your body

Traditionally, there are three kinds of amino acids: non-essential, essential, and conditional.

While your body can produce non-essential amino acids, it can’t make essential amino acids. As a result, you have to consume them as part of your diet.

Conditional amino acids are only needed if you’re sick or experiencing high levels of stress.

L-theanine is a different kind of amino acid, meaning it doesn’t fall into any of the three categories of amino acids listed above. And even though it’s an amino acid, it doesn’t build protein and your body doesn’t necessarily need it for survival

That said, it’s packed with benefits for your body. Let’s take a closer look at these benefits.

4 Benefits of L-Theanine

If you’re considering adding more of this amino acid to your diet, studies show that it may help improve your quality of sleep, manage your weight, prevent stress and anxiety, and support your immune system.

Keep reading to learn more about these incredible benefits.

1. Improves sleep

Do you struggle to get good quality sleep? Supplementing your diet with L-theanine may help.

Researchers conducted a double-blind experiment to study its effects on 8 to 12-year-old boys with ADHD. They randomly split the boys into two groups. The control group received a placebo, while the experimental group received 400 mg of L-theanine each day

Results showed that the boys who took L-theanine each day got better sleep than those who didn’t. After falling asleep, they were less likely to wake up during the night. [1]

The takeaway? You may also experience improved sleep quality if you include more L-theanine in your diet—either via natural forms such as green tea and mushrooms or in supplement form!

2. Supports healthy weight management

Did you know that L-theanine and sodium L-glutamate in green tea interact with glutamate receptors to produce an umami flavor? [2]

And while umami flavor is simply delicious (and that's a good enough reason to eat it), it can also help you manage your weight!

Research shows that umami flavor can help curb hunger while also making you feel full. [3] So, if you’re trying to lose weight, drinking more green tea or eating more mushrooms to up your L-theanine intake may help.

3. Fights stress and anxiety

If that weren’t enough, this beneficial amino acid also reduces stress and anxiety!

When you experience stress, your heart rate increases and the amount of immunoglobulin-A (IgA) in your saliva decreases. [4] This can make you more susceptible to illness.

Interestingly, research has shown that people who take L-theanine experience decreasing heart rates. It also keeps their IgA from lowering as much when they are stressed out. [5]

Finally, it may also improve symptoms of anxiety and depression—all of which are great reasons to consider including more L-theanine in your diet on a regular basis. [6]

4. Supports immune health

A healthy immune system can help you fight off all sorts of illnesses, from the common cold to cancer and more. Fortunately, L-theanine can help with this, too!

In a 28-day study, researchers split ducks into five groups with diets containing different amounts of L-theanine: 0 mg/kg, 300 mg/kg, 600 mg/kg, 900 mg/kg, and 1500 mg/kg

They measured the levels of immune system cells and other metabolic markers on days 14 and 28. The ducks whose diets were supplemented with L-theanine experienced increased immunoglobulins, which can help prevent infections. [7]


L-theanine - Dr. Pingel


L-Theanine Side Effects

Taking L-theanine is safe in most cases, but the long-term effects are unknown.

The most common side effects are an upset stomach, diarrhea, and headaches from the caffeine if you drink green tea to increase your L-theanine intake. Also, note that it may not be safe for pregnant or breastfeeding women or young children.

As always, you should talk to your preferred healthcare professional about any supplements or dietary changes you're considering. They can help you decide if it’s an appropriate plan for you, based on your unique medical history. 

Dosage for L-Theanine

Simply put, the appropriate dose of L-theanine for you depends on your needs

Studies show efficacy for reducing stress, managing weight, better sleep, and immune system improvements from doses as low as 100 mg to as high as 400 mg. Discuss your goals with a healthcare professional to help you choose the best dosage for you.

If you’re looking to consume L-theanine from its natural sources, note that one cup of green tea has just shy of 8 grams of L-theanine, while black tea contains nearly 25 grams. [8]

If you don’t want to drink multiple cups of tea each day, you can take an L-theanine supplement instead. Make sure to carefully research the brands that are available to choose one that is good quality

This is important because supplements aren’t regulated the same way as medications are, so the quality of each product may vary.


Key Takeaways

  • L-theanine is an amino acid that can help you sleep better, reduce your stress and anxiety, manage your weight, and support a healthy immune system.
  • Getting more L-theanine in your diet is simple and convenient. It’s available in green tea, mushrooms, and over-the-counter supplements.
  • Talk to your healthcare provider to see if L-theanine is safe for you. The long-term effects are unknown, and it may not be safe for young children or pregnant or breastfeeding women.
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