by Ari Magill, MD
A water mazea and a step-throughb test evaluated their cognitive skills. Restraint-induced stress resulted in profound impairment on the cognitive tests and increased levels of stress-induced biomarkers in the serum and brain, including serum cortisol and certain neurotransmitters. L-theanine administration prevented cognitive impairment and biomarker changes.
In a laboratory rat model, the impact of L-theanine on memory formation was assessed on a molecular level by studying the phenomenon of long-term potentiation (LTP), a molecular process whereby nerve cells become sensitized and linked to each through communication interfaces known as synapses.These studies show that L-theanine could circumvent the deleterious impact of stress on LTP formation.5,6 It was also shown to lower the animals’ elevated blood pressure.7
L-theanine has a tempering effect on caffeine-induced stimulation.1 Kelly et al examined the combined effects of L-theanine and caffeine in subjects who had to focus on a particular area of the screen (after given a cue) and locate one out of many targets.8 Caffeine aided in ultimate identification, but the ability to discriminate between correct and incorrect marks were enhanced when they gave participants a combination of the two agents.
Another study showed that L-theanine significantly improved performance in a task that required switching attentional focus, although it did not increase feelings of subjective alertness.9
One trial found that it significantly improved reaction time and performance of tasks requiring visual attention while increasing alpha wave activity and decreasing heart rate– but only in subjects who rated high on a self-reported anxiety questionnaire.10
Park et al suggests benefit in mild cognitive impairment (MCI).11 Patients scoring at the lowest end of MCI had significant improvement in a mental status exam after 16 weeks of taking a pill combining 60 mg of L-theanine with other green tea extracts.
Kuriyama et al investigated whether there was a relationship between green tea consumption and cognitive performance, and found that people who drank greater quantities of green tea had significantly decreased risk of cognitive impairment.12
Possible Mechanisms of Action
L-theanine also seems to work by counteracting excitotoxicity, a phenomenon where excessive excitation leads to nerve cell injury and death due to oxidative damage and other mechanisms. The substance binds to the same receptors as glutamate, the most common neurotransmitter in the brain that excites other nerve cells, but with greatly reduced affinity.14 However, it does not activate that receptor. By occupying the binding spot, glutamate cannot land there, resulting in nerve-cell relaxation without actively inhibiting them. It was also shown to inhibit glutamine build-up within both neurons and nerve cell helper cells.15
b Step-through exercise: a bright box is connected to a dark box by a “guillotine” door. The mouse is placed in the bright box with the connecting door closed and allowed to explore (although they instinctively prefer dark, hidden places). The connecting door is opened; the mouse will instinctively move through the door into the black box, but then receives a shock, so it has to learn to refrain from moving into the black box.
- Mason R. 200 mg of Zen: L-theanine boosts alpha waves, promotes alert relaxation. Altern Comp Therapies. 2001;7(2):91-95. https://doi.org/10.1089/10762800151125092.
- Finger A, et al. Chromatography of tea constituents. J Chromatogr. 1992;624(1-2):293-315. doi: 10.1016/0021-9673(92)85685-m.
- Rao TP, et al. Suntheanine: A pure and safe L-theanine dietary supplement for relaxation and stress relief. Neutraceuticals. 2007;1-2.
- Tian Xia, et al. Protective effect of l-theanine on chronic restraint stress-induced cognitive impairments in mice. Brain Res. 2013;1503:24-32. doi: 10.1016/j.brainres.2013.01.048.
- Takeda A, et al. Unique induction of CA1 LTP components after intake of theanine, an amino acid in tea leaves and its effect on stress response. Cell Mol Neurobiol. 2012;32(1):41-48. doi: 10.1007/s10571-011-9732-z.
- Tamano H, et al. Preventive effect of theanine intake on stress-induced impairments of hippocamapal long-term potentiation and recognition memory. Brain Res Bull. 2013;95:1-6. doi: 10.1016/j.brainresbull.2013.02.005.
- Juneja LR, et al. L-theanine—a unique amino acid of green tea and its relaxation effect in humans. Trends Food Sci Technol. 1999;10(6): 199-204.
- Kelly SP, et al. L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr. 2008;138(8):1572S-1577S. doi: 10.1093/jn/138.8.1572S.
- Einöther SJL, et al. L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite. 2010;54(2):406-409. doi: 10.1016/j.appet.2010.01.003.
- Higashiyama A, et al. Effects of l-theanine on attention and reaction time response. J Funct Foods. 2011;3.3:171-178. https://doi.org/10.1016/j.jff.2011.03.009.
- Park Sang-Ki, 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 Med Food. 2011;14(4):334-343. doi: 10.1089/jmf.2009.1374.
- Kuriyama S, et al. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project. Am J Clin Nutr. 2006;83(2):355-361. doi: 10.1093/ajcn/83.2.355.
- Siamwala JH, et al. L-theanine promotes nitric oxide production in endothelial cells through eNOS phosphorylation. J Nutr Biochem. 2013;2(3):595-605. doi: 10.1016/j.jnutbio.2012.02.016.
- Kakuda T, et al. Inhibition by theanine of binding of [3H] AMPA,[3H] kainate, and [3H] MDL 105,519 to glutamate receptors. Biosci Biotech Biochem. 2002;66(12): 2683-2686. doi: 10.1271/bbb.66.2683.
- Kakuda T, et al. Theanine, an ingredient of green tea, inhibits [3H] glutamine transport in neurons and astroglia in rat brain. J Neurosci Res. 2008;86(8):1846-1856. doi: 10.1002/jnr.21637.