Theanine (2002, '10-'12, '14, '18, '19) & Alzheimer's

L-theanine is theanine's chemical mirror image, and is most often tested. Long-term L-theanine administration has demonstrated facilitating long-term potentiation and an increase in brain-derived neurotrophic factor (BDNF) expression in the hippocampus over three to four weeks.^{1, 2} BDNF is a protein that protects survival of nerve cells. In addition there is mounting evidence supporting a neuroprotective effect.^{3, 4, 5} L-theanine treated Alzheimer's patients experienced reduced stress-related symptoms, such as sleep disturbances as well as cognitive improvements in verbal fluency and executive function.⁶

The combination of theanine and luteolin improved AD-like symptoms by increasing hippocampal insulin signaling power and decreasing neuroinflammation and norepinephrine degradation in animal models of AD. ^{7, 8}

Theanine is found in green tea.

Research

1. Wakabayashi C, Numakawa T, Ninomiya M, Chiba S, Kunugi H. (2012). Behavioral and molecular evidence for psychotropic effects in L-theanine. Psychopharmacology (Berl). Feb; 219(4):1099-109.
2. Tamano H, Fukura K, Suzuki M, Sakamoto K, Yokogoshi H, et al. (2014). Advantageous effect of theanine intake on cognition. Nutr Neurosci. Nov; 17(6):279-83.
3. Kakuda T, Nozawa A, Sugimoto A, Niino H. (2002). Inhibition by theanine of binding of [3H]AMPA, [3H]kainate, and [3H]MDL 105,519 to glutamate receptors. Biosci Biotechnol Biochem. Dec; 66(12):2683-6.
4. Kakuda T. (2011). Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction. Pharmacol Res. Aug; 64(2):162-8.
5. Di X, Yan J, Zhao Y, Zhang J, Shi Z, et al. (2010). L-theanine protects the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate-induced excitotoxicity via inhibition of the NMDA receptor pathway. Neuroscience. Jul 14; 168(3):778-86.
6. Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, et al. (2019). Effects of l-theanine administration on stress-related symptoms and cognitive functions in healthy adults: A randomized controlled trial. Nutrients. 2019;11(10):2362.
7. Park S, Kim DS, Kang S, Kim HJ. (2018). The combination of luteolin and l-theanine improved Alzheimer disease-like symptoms by potentiating hippocampal insulin signaling and decreasing neuroinflammation and norepinephrine degradation in amyloid-B-infused rats. Nutr Res. Dec;60:116-131.
8. Zhu G, Yang S, Xie Z, Wan X. (2018). Synaptic modification by L-theanine, a natural constituent in green tea, rescues the impairment of hippocampal long-term potentiation and memory in AD mice. Neuropharmacology. Aug;138:331-340.