Why should you take L-theanine?

Why should you take L-theanine?

L-theanine is a special amino acid that you can find in tea leaves (of the Camellia sinensis plant). Scientific studies have shown that supplementation with L-theanine helps you sleep better, be less anxious, relax, improve mental focus, and even boost your immune system! 

While there are some side effects to drinking a lot of green tea, there are no side effects when you take only the isolated L-theanine. This is why taking L-theanine supplements is an easy and efficient way to achieve calmness and have a good night's sleep without the side effects of caffeine. Of course, you should take the supplements in moderation under the recommended dosages. Find more info on this in the article below. 

If you are interested in purchasing L-theanine, have a look at what we offer here. 

L-theanine - Health Benefits 

As a molecule, L-theanine offers the following health benefits:

  • It is an antioxidant,
  • It works anti-inflammatory,
  • It is neuroprotective,
  • It protects of the cardiovascular, kidney, liver, urinary, and intestinal systems. 

L-theanine helps the body deal with stress and anxiety by affecting the concentrations of serotonin and dopamine in the brain. As a consequence, the levels of the stress hormone cortisol decrease, your blood pressure drops, and you begin to relax. For these reasons, L-theanine can help you be less anxious and sleep better. 

Other than that, L-theanine can improve your focus and cognitive abilities, such as solving simple tasks. Interestingly, L-theanine also has a very strong influence on boosting your immune system and helping you fight the common cold or flu.

There are some claims that L-theanine helps with weight loss as well, but these were not scientifically confirmed. Although there may be a correlation between drinking green tea (or taking L-theanine), and losing weight, it is unlikely that L-theanine is directly responsible for it. 

Read more about green tea and the green tea extract here

L-theanine - Scientific Studies

Even though there are many more studies done on the effects of L-theanine on laboratory animals, there is an equally important number of studies done on humans in clinical trials

As an example, several smaller clinical trials looked into the effect of L-theanine on mental health, particularly on stress, anxiety, depression, and attention The overall conclusion is that L-theanine significantly helps decrease the levels of stress and improve sleep, cognitive abilities, and focus. You can find a review of these studies here (1). 

L-theanine and caffeine in combination had a combined effect on improving cognitive function and attention in young healthy male individuals (2). If you take L-theanine together with caffeine, it might work even better for your mental clarity and attention span

Furthermore, several clinical trials showed that L-theanine supplementation helped both younger and elderly people, as well as healthcare workers, fight the common cold and prevent them from getting the flu. You can find the summary of these findings here (3).

L-theanine - Side Effects

There are no known side effects of taking L-theanine supplements. There are some side effects to drinking large amounts of green tea, such as nausea and upset stomach, but this is not due to high L-theanine amounts. 

Another common question about this supplement is: does L-theanine affect blood pressure? The answer is yes, one of the health benefits of L-theanine is to lower blood pressure, especially after stressful situations. If you are taking blood pressure-reducing medication, it is advisable not to additionally take L-theanine. This might result in your blood pressure being too low and possibly dangerous. 

Always discuss taking new supplements with your doctor or healthcare provider first, especially if you're pregnant, breastfeeding, or regularly taking any medication.  

L-theanine - Dosage Guide

As L-theanine is a fairly new supplement on the market, there are no proper regulations about its dosage. However, several clinical trials tested L-theanine supplementation in humans and found no side effects. 

Multiple clinical trials showed that 450-900 mg per day were safe and effective. 


Literature sources:

  1. Williams, J.; Kellett, J.; Roach, P.D.; McKune, A.; Mellor, D.; Thomas, J.; Naumovski, N. l-Theanine as a Functional Food Additive: Its Role in Disease Prevention and Health Promotion. Beverages 2016, 2, 13. https://doi.org/10.3390/beverages2020013
  2. Kahathuduwa CN, Dassanayake TL, Amarakoon AMT, Weerasinghe VS. Acute effects of theanine, caffeine and theanine-caffeine combination on attention. Nutr Neurosci. (2017) 20:369–77. 10.1080/1028415X.2016.1144845
  3. Li MY, Liu HY, Wu DT, Kenaan A, Geng F, Li HB, Gunaratne A, Li H, Gan RY. L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications. Front Nutr. 2022 Apr 4;9:853846. doi: 10.3389/fnut.2022.853846
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