Theanine, stress, anxiety and cancer: Review

Theanine, stress, anxiety and cancer: Review

L-Theanine is an amino acid in green tea and certain mushrooms; in its purified formit has been shown to reduce stress and anxiety and improve cognitive function; it also has a significant number of benefits with cancer pathways.


Theanine and amino acids


There are 22 amino acids that go to make up our human proteins. Nine are essential (we have to obtain them from our foods), the other 13 we can make for ourselves. Just to complicate matters, in nature there are probably at least 200 amino acids. The difference is that the ones we humans use to make proteins are α-amino acids. The rest aren’t.


α-amino acids are involved in proteins, enzymes, muscles and tissues, but they can also neurotransmitter synthesis and brain function so they are essential to our lives being involved in our structure and every process in our fully functioning bodies.


L-Theanine is one of the greater 200 amino acids - a non-protein amino acid - found in tea leaves, green, white or black, and certain mushrooms. It can be found in a purified form as a supplement. It sometimes works best when pairing it with another compound.


Theanine and Umami


Theanine was first discovered by scientist, Kikunae Ikeda, looking into the difference between sweet, sour and savoury tastes - Savoury is referred to as 'Umami' in Japan. A key component in Umami is  L-Theanine. It is also in foods from chocolate to grapefruit - they would have a bitter taste without it. Umami flavouring led Ikeda to develop Monosodium Glutamate (MSM) after realising that glutamate was key to Umami. 


Theanine, neurotransmitters, the brain and sleep


L-Theanine can promote sleep by producing a number of neurotransmitters - calming influences in the brain - GABA, serotonin, and dopamine. L-Theanine also reduces levels of chemicals in the brain that are linked to stress and anxiety (1).

It also seems theanine can up-regulate Slc38a1 expression which activates the intracellular mTOR signalling pathway in the brain required for neurogenesis - the process by which nervous system cells, the neurons, are produced by neural stem cells. Put simply, theanine helps you make a healthier nervous system (2). Some claim it helps you focus.

A radomised controlled trial where participants took L-Theanine for 4 weeks certainly showed they were calmer at the end with improved cognitive function (3). The researchers from Tokyo felt this compound could help with mental issues in our modern world.

Theanine and cancer

A review of in vivo studies on the benefits with Theanine and cancer showed that it had a clear influence on the risk of cancer and its progression. Theanine seems to influence multiple cancer pathways, e.g. EGFR, VEGFR, Met, and Akt/mTOR, JAK2/STAT3, and ERK/NFκB pathways. It also activates apoptosis and caspase-independent programmed cell death pathways. It restricts progression and proliferation (4).

Theanine, lung cancer, leukaemia

At Canceractive, we first noticed its benefits with Non Small Cell Lung Cancer. In a study that also used leukaemia tissue, both in vitro and in vivo, theanine enhanced the effectiveness of the drugs used (5). In a second study on lung cancer, L-theanine was shown to inhibit cancer stem cells causing chemo-resistance by regulating the signalling pathways STAT3/NOTCH1-BMAL 1.

Theanine and prostate cancer

In another in vitro and in vivo study, this time in 2021, L-theanine could suppress invasion, migration, and affect multiple cancer pathways. The researchers concluded that the multiple findings meant that theanine should be considered as a promising candidate for antimetastatic therapy of prostate cancer (6). 

Theanine and Melanoma

In 2022, L-Theanine was shown to have an anti-cancer effect on melanoma cells by blocking proliferation and migration, and promoting apoptosis and this was dependent on the regulation of the clock gene Bmal1 (7).

Theanine - an overview. 

Chris Woollams, former Oxford University Biochemist and a founder of CANCERactive writes,”If you start with the researched benefits of lowered stress and anxiety levels, it is quite plausible that theanine could help restrict cancer and cancer pathways. Only recently we have reviewed two studies here and here on stress hormones and their ability to promote inflammation and cancer, angiogenesis, growth, progression and recurrence. More research on L-Theanine would be helpful, though”.

Go to: Stress hormones linked to breast cancer spread, angiogenesis and recurrence




  1. What You Need to Know About L-theanine; Michael J. Breuz; Aug 29, 2017; Psychology Today

  2. The role of glutamine in neurogenesis promoted by the green tea amino acid theanine in neural progenitor cells for brain health; Yukio Yoneda et al; eurochem Int; 2019 Oct;129:104505

  3. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial; Shinsuke Hidese et al; Nutrients; 2019 Oct 3;11(10):2362

  4. Theanine and cancer: A systematic review of the literature; Sara Shojaei-Zarghani et al;   Phytother Res, 2021 Sep;35(9):4782-4794.

  5. Effects of theanine on growth of human lung cancer and leukemia cells as well as migration and invasion of human lung cancer cells; Quin Liu et al; Cytotechnology. 2009 Apr; 59(3): 211–217.

  6. L-theanine suppresses the metastasis of prostate cancer by downregulating MMP9 and Snail; Xirui Fan et al; J Nutr Biochem; 2021 Mar;89:108556.

  7. L-Theanine inhibits melanoma cell growth and migration via regulating expression of the clock gene BMAL1; Ruyi Zhang et al; Eur J Nutr; 2022 Mar;61(2):763-777.




  Approved by the Medical Board.  Click Here



2023 Research
CancerAcitve Logo
Subscribe (Free e-Newsletter)

Join Chris'

Join Chris' NewsletterSignup today for free and be the first to get notified on new updates.