What Are The Benefits Of L-Theanine?

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Obi Obadike

Obi Obadike

Celebrity Fitness & Nutrition Expert, CFT, SFN, M.S. Founder & CEO – Ethical Inc.
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What are the benefits of L-Theanine?  Some of the benefits of L-Theanine are improving anxiety, focus, stress, concentration, reduce insomnia, and even helping to regulate blood pressure levels. L-theanine is an amino acid that is found in green and black tea.

There was a review of 5 controlled trials studies that had 104 participants that took L-theanine. And the result was reduced anxiety and stress in stressful conditions.

There was another study published in the Journal Of Clinical Psychiatry that focused on people living with schizophrenia disorder. Researchers found that it decreased anxiety and improved their symptoms in that research group.

What are the benefits of L-Theanine? iStock-natatravel


There was a small study that found a group that took L-theanine and caffeine and it helped a group of students focus better during their difficult school tasks. The amount of caffeine they took was 40 mg of caffeine.


There was also research that suggests that l theanine can improve the body’s immune system. A study published in the journal found that beverages that contain L-theanine helped decrease upper respiratory tract infections.

Another study found that green tea catechins that contain L-theanine could be effective at preventing the flu.

Blood Pressure

There was a study that found that people who experienced high blood pressure found that taking L-theanine helped reduce an increase in blood pressure. Also, a study showed that taking 200 mg of L-theanine helped reduce their resting heart rate.

Side Effects

There are no reported side effects if you take L-theanine.  But as we know L-theanine is found in tea so the side effects of drinking large amounts of black and green tea are:

  • Nausea
  • Upset Stomach
  • Irritability

Before taking an L-theanine supplement it is best to consult a medical professional if you need it and how much you need.

“Some of the benefits of L-Theanine are improving anxiety, focus, stress, concentration, reduce insomnia, and even helping to regulate blood pressure levels.” Celebrity Fitness & Nutrition Expert Obi Obadike

The Bottom Line is taking an L-theanine supplement has tremendous health benefits such as improving anxiety, focus, stress, concentration, reduction in insomnia, regulating blood pressure levels, etc.

If you have any interest in trying any of our Ethical Supplement products to help you heighten your immune system or assist you with your fitness, weight loss or health goals.

You can get a discount below at this link. ?utm_source=blog


  1. Williams J, Kellett J, Roach PD, 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(2):13.
  2. Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012 Oct 29;31(1):28. doi: 10.1186/1880-6805-31-28. PMID: 23107346; PMCID: PMC3518171.
  3. Matsumoto K, Yamada H, Takuma N, Niino H, Sagesaka YM. Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial. BMC Complement Altern Med. 2011 Feb 21;11:15. doi: 10.1186/1472-6882-11-15. PMID: 21338496; PMCID: PMC3049752.
  4. Mijong Park, Hiroshi Yamada, Kumi Matsushita, Shinya Kaji, Takahiro Goto, Yuko Okada, Kazuhiro Kosuge, Toshiro Kitagawa, Green Tea Consumption Is Inversely Associated with the Incidence of Influenza Infection among Schoolchildren in a Tea Plantation Area of Japan, The Journal of Nutrition, Volume 141, Issue 10, October 2011, Pages 1862–1870,
  5. Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010 Dec;13(6):283-90. doi: 10.1179/147683010X12611460764840. PMID: 21040626.
  6. Lyon MR, Kapoor MP, Juneja LR. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev. 2011 Dec;16(4):348-54. PMID: 22214254.
  7. Ota, M., Wakabayashi, C., Sato, N., Hori, H., Hattori, K., Teraishi, T., . . . Kunugi, H. (2015). Effect of l-theanine on glutamatergic function in patients with schizophrenia. Acta Neuropsychiatrica, 27(5), 291-296. doi:10.1017/neu.2015.22

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