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Tea Time for Fido and Fluffy?
Posted: April 22, 2011, 6:50 p.m., EDT
By Narda Robinson, DO, DVM
Snuggling up with a cup of warm tea conjures memories of relaxing moments. However, can tea or its derivatives benefit the brain and behavior of stressed-out dogs and cats? Is tea safe for non-humans? Wouldn’t it lead to more profound agitation from the caffeine?
The answers to all these questions center on the delivery mechanism. That is, a chemical constituent isolated from tea is now showing up in animal supplements for stress, anxiety and cognitive dysfunction.
This amino acid l-theanine (or “theanine”) supports a variety of biological processes; it is found nearly exclusively in tea, constituting between 1 and 2 percent of its dry weight.1 It is considered the most important amino acid found in this common beverage, out of several described.2
From a sensory perspective, theanine gives green tea its “sweet umami taste note.” Biochemically, it aids in the biosynthesis of polyphenols, which help neutralize free radicals.3 But theanine offers more than merely antioxidant benefits. Theanine enjoys an ease of entry into the nervous system. It readily crosses the blood-brain barrier in a dose-dependent fashion, delivering changes in mental processing soon after assimilation.
Various factors and mechanisms account for theanine’s multifaceted soothing impact. In the whole plant form, theanine in tea leaves seems to antagonize or offset the stimulatory effect of caffeine.4 As an isolated amino acid, however, theanine promotes predominantly relaxation. This takes place most notably through its effects on gamma-aminobutyric acid (GABA).
GABA participates in as many as half the synapses in the mammalian central nervous system.5 As the major inhibitory neurotransmitter found throughout the brain, GABA receptors exist in high concentration in the cortex, hippocampus, thalamus, basal ganglia and cerebellum. Yet theanine affects more than just GABA; it significantly increases dopamine in the striatum and serotonin in the striatumI, hippocampus and hypothalamus.6-7 These brain centers control motor control, limbic functions and autonomic drive.
From a clinical standpoint, theanine has already shown value for humans with schizophrenia and schizoaffective disorders; l-theanine added to antipsychotic drug therapy regimens ameliorated anxiety and psychotic features.8
Another approach, targeted amino acid therapy (TAAT), utilizes focused nutritional intervention according to results obtained from a broad-spectrum urine assay of neurotransmitter levels as biomarkers. This mental health treatment method has been studied for behaviorally at-risk adopted human children with presumed neurotransmitter imbalances.9
In one study, psychologists found that behavior problems such as aggression, depression and anxiety co-occur with sub-optimal levels of the neurotransmitters serotonin and GABA. Neurochemical intervention involving administration of theanine and a serotonin precursor both improved neurotransmitter biomarkers and lessened reports of acting out.10
Although TAAT is still in its infancy as a nutritional approach to psychological problems in humans, perhaps a veterinary version of TAAT could one day be designed for dogs and cats with psychological disturbances.
Theanine may also serve to salvage cognitive function. In certain areas of the brain, such as the hippocampus (a limbic system structure involved with learning and memory), theanine has been thought to inhibit glutamate reuptake and glutamate receptor blockade. Perhaps this results in improved function within certain brain structures. However, while its chemical structure resembles glutamic acid, an excitatory neurotransmitter, theanine appears to act more as a modulator of central nervous system function, performing a regulatory role that “tones down” neuronal responses.11
Recent work studying rats’ brains suggests that theanine inhibits transportation of glutamine across plasma membranes in neurons and astroglia. This finding has led some researchers to postulate that daily intake of theanine could perform a prophylactic function against a variety of neurodegenerative processes linked to overactivation of glutaminergic neurotransmission and its resultant neurotoxicity.12
Furthermore, a recently published paper from Korea indicated theanine possesses mast cell-stabilizing capability.13 The authors described experiments in rodents showing that theanine inhibited mast cell-mediated anaphylactic reactions. It also blocked activation of nuclear factor-kappa B and RIP-2/capsase-1, resulting in a decrease of pro-inflammatory cytokines such as tumor necrosis factor-alpha, IL-1beta, IL-6, and IL-8.
Given the involvement of inflammation in several neurodegenerative processes, the ability of theanine to reduce inflammation in the nervous system may aid in its protection against cognitive deterioration. In another just-released Korean trial, human patients suffering from mild cognitive impairment experienced improved memory and attention after ingesting green tea extract and l-theanine.14
Providing theanine as a free amino acid rather than powdered plant leaves removes concerns about caffeine. Quality control, always a question in the under-regulated supplement industry, becomes more manageable when theanine is included as an amino acid rather than green tea extract. One manufacturer of a theanine-containing canine supplement even touts the absence of herbal ingredients such as kava kava, valerian and St. John’s wort, implying the omission enhances safety.15
With a step forward in supplement regulation, the National Institute of Standards and Technology has joined forces with other agencies such as the National Institutes of Health and the Food and Drug Administration to create dietary supplement Standard Reference Materials (SRMs).16 With SRMs, chemists can analyze chromatograms of agents such as theanine, refine assay methods, and compare results of well-characterized compounds (SRMs) to commercial supplement preparations.
Knowing accurately what a product contains contrasts sharply with the mystery contents of Asian herbal remedies, notably Chinese mixtures with insects, reptiles and worms along with plant material, making it hard to know what is intentionally added and what is contaminant.
As our understanding of the molecular mechanism of action of theanine matures, investigations can then focus on whether theanine might function as an anesthesia adjunct, reducing the dose of pharmaceuticals required and thereby augmenting safety.
Dr. Robinson, DVM, DO, Dipl. ABMA, FAAMA, oversees complementary veterinary education at Colorado State University.
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FOOTNOTES
1. Bryan J. Psychological effects of dietary components of tea: caffeine and l-theanine. Nutrition Reviews. 2007;66(2):82-90.
2. Alcazar A, Ballesteros O, Jurado JM, et al. Differentiation of green, white, black, oolong, and Pu-erh teas according to their free amino acids content. J Agric Food Chem. 2007;55:5960-5965.
3. Alcazar A, Ballesteros O, Jurado JM, et al. Differentiation of green, white, black, oolong, and Pu-erh teas according to their free amino acids content. J Agric Food Chem. 2007;55:5960-5965.
4. Rogers PJ, Smith JE, Heatherley SV, et al. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology. 2008;195:569-577.
5. Young AB and Chu D. Distribution of GABAA and GABAB receptors in mammalian brain: potential targets for drug development. Drug Development Research. 1990;21:161-167.
6. Bryan J. Psychological effects of dietary components of tea: caffeine and l-theanine. Nutrition Reviews. 2007;66(2):82-90.
7. Heese T, Jenkinson J, Love, C, et al. Anxiolytic effects of l-theanine – a component of green tea – when combined with midazolam, in the male Sprague-Dawley rat. AANA Journal. 2009;77(6):445-449.
8. Ritsner MS, Miodownik C, Ratner Y, et al. L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. J Clin Psychiatry. 2011;72(1):34-42.
9. Cross DR, Kellermann G, McKenzie LB, et al. A randomized targeted amino acid therapy with behaviourally at-risk adopted children. Child: Care, Health and Development. 2010; December 20. Epub ahead of print.
10. Cross DR, Kellermann G, McKenzie LB, et al. A randomized targeted amino acid therapy with behaviourally at-risk adopted children. Child: Care, Health and Development. 2010; December 20. Epub ahead of print.
11. Bryan J. Psychological effects of dietary components of tea: caffeine and l-theanine. Nutrition Reviews. 2007;66(2):82-90br /> 12. Kakuda T, Hinoi E, Abe A, et al. Theanine, an ingredient of green tea, inhibits {3H] glutamine transport in neurons and astroglia in rat brain. J Neuroscience Res. 2008;86:1846-1856.
13. Kim NH, Jeong JH, and Kim HM. Theanine is a candidate amino acid for pharmacological stabilization of mast cells. Amino Acids. 2011 Feb 23 [Epub ahead of print].
14. Park S-K, Jung I-C, Lee WK, et al. A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study. J Medicinal Food. 2011;14(4):1-10.
15. Vetriscience ® Laboratories. Composure. Product information. See www.vetriscience.com .
16. Bedner M, Sander LC, and Sharpless KE. An LC-ESI/MS method for determining theanine in green tea dietary supplements. Anal Bioanal Chem. 2010;397:1773-1777.
17. Heese T, Jenkinson J, Love, C, et al. Anxiolytic effects of l-theanine – a component of green tea – when combined with midazolam, in the male Sprague-Dawley rat. AANA Journal. 2009;77(6):445-449.
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