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L-Theanine: Good for What Ails You and Your Neurotransmitters

by Dr.Dave on Aug 3, 2014     

Have you ever wondered why so many treatment recommendations include, either by itself or in combination with other ingredients, the supplement L-theanine? Why is that? What is this important compound and where does it come from? In this brief article, I hope to shed some light on these frequently asked questions.

First, let’s review a basic concept that may be news to you. Many of the symptoms and much of the damage associated with depression, anxiety, and other brain maladies stems from abnormally elevated levels of one of your key neurotransmitters: glutamate.

The Glutamate-GABA Connection

Glutamate is the major excitatory neurotransmitter in your brain. It is crucial for, among other functions, learning and memory. Low levels can lead to fatigue, “brain fog,” and poor memory. Increased levels of glutamate, on the other hand, cause numerous symptoms and can even kill your brain cells. Glutamate imbalance has been shown to be involved in many neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Huntington’s, Tourette’s, delirium, depression, OCD, and autism.

Your natural counterbalance to excess glutamate is the amino acid gamma-aminobutyric acid (GABA). Most of the nervous system disorders mentioned above are not only associated with elevations of glutamate but also with low levels of GABA.

The Many Actions of L-Theanine

This mismatch between glutamate and GABA is where L-theanine comes into the picture. Although we stress the need to personalize your treatment based on specific psycho-neuro-immunological perturbations (PNIPs), L-theanine is one of those versatile supplements that provides general support in most areas of neurotransmitter imbalance.

To better understand this notion, let’s take a closer look at some of L-theanine’s specific actions:

  • L-theanine directly mimics the calming effects of your natural GABA
  • L-theanine also helps you make more of your own GABA
  • It is believed that L-theanine’s effects are due to its ability to block glutamate receptors, thereby dampening the ravages of excessive glutamate activity
  • By blocking glutamate receptors, L-theanine indirectly supports GABA activity by freeing it to perform other important duties

Due to these multiple mechanisms, L-theanine is often referred to as, the “adaptogen” of neurotransmitters – similar to the concept of herbs such as rhodiola in adrenal fatigue. It has been recognized for centuries as having relaxant properties. A unique amino acid, L-theanine is the biologically active constituent of green tea, which has been widely studied for its ability to produce a calming effect and prevent over-stimulation.

Because it supports GABA activity, L-theanine is a solid treatment consideration when your calming neurotransmitters (GABA and serotonin) levels have been documented below. Additionally, L-theanine promotes both neuroinhibitory and parasympathetic responses. As a result, it is useful when you are experiencing elevations of your excitatory neurotransmitters including dopamine, norepinephrine and epinephrine.

Furthermore, L-theanine promotes the release of serotonin and dopamine, and, as such, may be included in a well-rounded treatment plan – particularly when additional neurotransmitter imbalances are present.

Importantly, L-theanine helps you relax without making you drowsy or fatigued.

L-theanine is commonly dosed 2-3 times daily to account for its relatively short half-life. Although stand-alone L-theanine represents a reasonable go-to therapy for treatment of neurotransmitter imbalances, it is most often used as a component in a more comprehensive supplementation program.

Although L-theanine is a good bet for any number of neurochemical imbalances, determining specific neurotransmitter disarray through our urinary neurotransmitter testing is an easy and accurate means to identify excess or deficiency for targeted treatment.


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  2. Nathan PJ, Lu K, Gray M, Oliver C. J Herb Pharmacother. 2006;6(2):21-30.
  3. Yamada T, Terashima T, Kawano S, et. al. Amino Acids. 2009 Jan;36(1):21-7.
  4. Yokogoshi H, Kobayashi M, Mochizuki M, Terashima T. Neurochem Res 1998;23:667-673.
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