L-Theanine in Focus for Cognitive Function

The magic of L-theanine lies in its ability to increase activity of alpha brain waves, which induce a feeling of calm relaxation, without causing drowsiness.¹ A study investigating the effect of 250 mg of L-theanine on alpha brain waves in subjects found that L-theanine had a significant effect on the general state of mental alertness, and plays a more general role in “…facilitating longer-lasting processes responsible for sustaining attention across the timeframe of a difficult task...”²

Another study explored the combined effects of 250 mg of L-theanine plus 150 mg of caffeine with similar findings. Visual information processing and mental fatigue ratings improved; faster reaction times, numeric working memory reaction times, and improvements in word recognition reaction times were all reported in the L-theanine and caffeine group.³ A separate study examining the ability of participants to maintain focus on monotonous tasks over a two-hour period, showed that those taking a combination of 100 mg of L-theanine plus 50 mg of caffeine had a significant reduction in errors compared to an increase in errors in the placebo group.⁴

Even without the addition of caffeine, L-theanine delivers. A 12-week randomized, placebo-controlled study looking at the effects of 100 mg of L-theanine on cognitive function showed positive results after one dose. After just a single dose of L-theanine, subjects saw an improvement in attention tasks, an increase in the number of correct answers, and a decrease in the number of errors in working memory tasks. The researchers concluded, “Our study indicated that L-theanine may contribute to improving attention, thus enhancing working memory and executive functions.”⁵

L-Theanine for High Anxiety

L-theanine also supports attention, learning, and reaction times in those with high anxiety. One study on L-theanine in college-aged subjects backs this up. Eighteen subjects were classified as either having high anxiety or minimal/low anxiety and were separated into those respective groups. Both groups were given 200 mg of L-theanine and a placebo over the duration of the study. Fifteen to 60 minutes after taking L-theanine or placebo, they underwent assessments on visual and audio attention and response tests. The results on anxiety markers showed “a significant enhanced activity of alpha [waves], descending heart rate, elevated visual attentional performance, and improved reaction time response among high-anxiety propensity subjects compared to a placebo.” The study concluded, “Results evidently demonstrated that L-theanine clearly has a pronounced effect on attention performance and reaction time response in normal healthy subjects prone to have high anxiety.”⁶   They noted that no significant differences were evident among subjects with minimal anxiety.

Stress Less, Sleep Better with L-Theanine

Another randomized, placebo-controlled study looked at the effects of taking 200 mg of L-theanine daily for four weeks on stress-related symptoms, sleep, and cognitive function. The 30 participants were healthy adults 48 years and older. The Self-Rating Depression Scale, State-Trait Anxiety Inventory-Trait, and Pittsburg Sleep Quality Index (PSQI) scores all improved after taking L-theanine. Furthermore, scores for sleep latency (amount of time it takes to fall asleep), sleep disturbance, and use of sleep medication all were reduced in the L-theanine group, compared to the placebo group.⁷

The same study found that when it came to cognitive function, verbal fluency, and executive function, scores improved after L-theanine administration, especially letter fluency (naming as many words as possible that start with a specific letter in a specified amount of time) when compared to those taking a placebo. They summarized, “Our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.” Other research has found theanine reduces stress-induced rises in blood pressure, another way it supports the whole body under stress.⁸

Combat Depression with L-theanine

When there’s a chemical imbalance in the brain, there’s no one-size-fits-all answer. Maintaining your mental health means taking a multifaceted approach—implementing things like talk therapy, regular self-care, nutrition, exercise, vitamins, and supplements daily. L-theanine is one of those supplements that shows promise in helping combat depression at the source.  

In one study, L-theanine was examined for its effectiveness in patients with major depressive disorder (MDD). Findings revealed that after eight weeks of 250 mg/day of L-theanine depression and anxiety scores decreased and sleep scores improved. Cognition, verbal memory, and executive function were also enhanced, and error rate decreased. They concluded, “…L-theanine administration is safe and has multiple beneficial effects on depressive symptoms, anxiety, sleep disturbance, and cognitive impairments in patients with MDD.”⁹

Another study investigating the effects of L-theanine on an animal model of depression showed that rats with chronic mild stress and depression symptoms experienced a significant increase in neurotransmitters such as serotonin, norepinephrine, and dopamine after administration of L-theanine. The researchers summarized that L-theanine possibly had antidepressant-like effects.¹⁰

Protect Cognitive Function with L-theanine 

Beyond calm and focus, L-theanine appears to have a protective effect on brain function. In studies of older adults with mild to moderate cognitive decline, L-theanine supplementation improves attention and memory both acutely and after long term use.^{11 12} Getting at least some theanine from green tea may offer additional benefits, since green tea is rich in polyphenols that may modulate inflammation and protect against oxidative damage in the brain as we age.^{11 13 14}

Don’t let a scattered, stressed-out, sleep-deprived day get in the way of your true potential. Reach for L-theanine for the cool calm!

References

1. Nobre, A. C., Rao, A., & Owen, G. N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific journal of clinical nutrition, 17 Suppl 1, 167–168. Retrieved 12 May 2023 from https://apjcn.nhri.org.tw/server/APJCN/17%20Suppl%201/167.pdf .
2. Gomez-Ramirez, M., Kelly, S. P., Montesi, J. L., & Foxe, J. J. (2009). The effects of L-theanine on alpha-band oscillatory brain activity during a visuo-spatial attention task. Brain topography, 22(1), 44–51. https://doi.org/10.1007/s10548-008-0068-z
3. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., & Scholey, A. B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood. Biological psychology, 77(2), 113–122. https://doi.org/10.1016/j.biopsycho.2007.09.008
4. Foxe, J. J., Morie, K. P., Laud, P. J., Rowson, M. J., de Bruin, E. A., & Kelly, S. P. (2012). Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. Neuropharmacology, 62(7), 2320–2327. https://doi.org/10.1016/j.neuropharm.2012.01.020
5. Baba, Y., Inagaki, S., Nakagawa, S., Kaneko, T., Kobayashi, M., & Takihara, T. (2021). Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. Journal of medicinal food, 24(4), 333–341. https://doi.org/10.1089/jmf.2020.4803
6. Higashiyama, A., Htay, H.H., Ozeki, M., Juneja, L.R., Kapoor, M.P. (2011). Effects of L-theanine on attention and reaction time response. J Functional Foods, 3(3), 171-178. https://doi.org/10.1016/j.jff.2011.03.009
7. Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), 2362. https://doi.org/10.3390/nu11102362
8. Yoto, A., Mokoki, M., Murao, S., Yokogoshi, H. (2012). Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol, 31(1), 28. doi: 10.1186/1880-6805-31-28
9. Hidese, S., Ota, M., Wakabayashi, C., Noda, T., Ozawa, H., Okubo, T., & Kunugi, H. (2017). Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta neuropsychiatrica, 29(2), 72–79. https://doi.org/10.1017/neu.2016.33
10. Shen, M., Yang, Y., Wu, Y., Zhang, B., Wu, H., Wang, L., Tang, H., & Chen, J. (2019). L-theanine ameliorate depressive-like behavior in a chronic unpredictable mild stress rat model via modulating the monoamine levels in limbic-cortical-striatal-pallidal-thalamic-circuit related brain regions. Phytotherapy research : PTR, 33(2), 412–421. https://doi.org/10.1002/ptr.6237
11. Schor, J. (2014, March 21). Green tea and l-theanine in mild cognitive impairment. Natural Medicine Journal. Retrieved from https://www.naturalmedicinejournal.com/journal/green-tea-and-l-theanine…
12. Baba, Y., Inagaki, S., Nakagawa, S., Kaneko, T., Kobayashi, M., Takihara, T. (2021). Effects of L-theanine on cognitive function in middle-aged and older subjects: a randomized placebo-controlled study. J Med Food, 24(4), 333-341. doi: 10.1089/jmf.2020.4803
13. Kakuda T. Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction. Pharmacological Research. 2011;64(2):162-168.
14. Kim, TI, Lee YK, Park SG, Choi IS, et al. L-theanine, an amino acid in green tea, attenuates β-amyloid-induced cognitive dysfunction and neurotoxicity: Reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-κB pathways. Free Radical Biology and Medicine. 2009; 47(11):1601-1610.