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Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study.
Furushima, D, Sugiyama, I, Nomura, Y, Unno, K, Yamada, H
Journal of nutritional science and vitaminology. 2022;68(6):540-546
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The beneficial effects of green tea and its components are well known. The ingredient L-Theanine is the most abundant water soluble non-proteinous amino acid component in green tea. The second most abundant ingredient is L-Arginine. It also exhibits a high stress-reducing effect. The hypothesis of this study was that the combined ingestion of L-arginine and L-theanine could have beneficial clinical effects for psychological stress compared with ingestion of theanine alone. This study was a randomised placebo-controlled, single-blinded study in healthy young adults. Participants (n=120) were randomly assigned to one of the three groups (1:1:1); L-theanine alone, L-theanine and L-arginine or placebo. Results show that combined ingestion of L-theanine and L-arginine tended to have greater stress reducing effects than ingestion of L-theanine alone. However, the difference was not statistically significant. Authors conclude that their findings are suggestive of synergistic effects of L-theanine and L-arginine against stress in young adults.
Abstract
l-Theanine, the most abundant amino acid component in green tea, has anti-stress effects and refreshes the mental state. A recent study demonstrated that l-arginine, the second most abundant amino acid in green tea, might enhance the anti-stress effects of l-theanine. The aim of this study was to evaluated the effects of combined ingestion of l-theanine and l-arginine on psychological stress in humans. A randomized placebo-controlled trial was conducted including 120 healthy young adults (mean age 22.4 y, 63.3% female). Subjects were randomly assigned to theanine (200 mg l-theanine), combined theanine/arginine (200 mg l-theanine, 50 mg l-arginine), or placebo groups. After consuming a test beverage, we administered a stress-loading test (Uchida-Kraepelin performance test) and performed salivary alpha-amylase activity (sAA) measurements to assess the physiological stress response at 0 min (immediately after), 5 min, and 15 min. The changes in sAA at 15 min after the stress-loading test were -2.75 (11.2) kIU/L in the theanine/arginine group, -0.40 (11.5) kIU/L in the theanine group, and 6.95 (18.6) kIU/L in the placebo group. The values in the theanine/arginine (p=0.007) and theanine (p=0.02) groups differed significantly from those in the placebo group. However, the difference between theanine/arginine and theanine groups, was not statistically significant (p=0.74). From this study, no clear conclusion could be drawn regarding the potentiating effect of theanine and arginine combined ingestion on anti-stress effects in human.
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Mechanisms Underlying the Anti-Depressive Effects of Regular Tea Consumption.
Rothenberg, DO, Zhang, L
Nutrients. 2019;11(6)
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Previous research suggests that tea consumption is linked to a lower risk of depression, but it is not understood why. This meta-analysis and literature review looked at previous human, animal and laboratory studies that might give an indication of the mechanisms by which drinking tea can lead to a reduced depression risk. Tea contains many different active compounds such as L-theanine, various polyphenols and polyphenol metabolites that have effects on the immune system, stress response, brain neurotransmitters such as serotonin and dopamine, and gut bacteria. Different types of tea such as black, green or oolong tea contain different amounts of active compounds. The authors found that these compounds are capable of functioning through multiple pathways simultaneously that together reduce the risk of depression. The authors concluded that daily consumption of moderate amounts of different types of tea may offer significant potential benefit in the risk reduction of depression.
Abstract
This article is a comprehensive review of the literature pertaining to the antidepressant effects and mechanisms of regular tea consumption. Meta-data supplemented with recent observational studies were first analyzed to assess the association between tea consumption and depression risk. The literature reported risk ratios (RR) were 0.69 with 95% confidence intervals of 0.62-0.77. Next, we thoroughly reviewed human trials, mouse models, and in vitro experiments to determine the predominant mechanisms underlying the observed linear relationship between tea consumption and reduced risk of depression. Current theories on the neurobiology of depression were utilized to map tea-mediated mechanisms of antidepressant activity onto an integrated framework of depression pathology. The major nodes within the network framework of depression included hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, inflammation, weakened monoaminergic systems, reduced neurogenesis/neuroplasticity, and poor microbiome diversity affecting the gut-brain axis. We detailed how each node has subsystems within them, including signaling pathways, specific target proteins, or transporters that interface with compounds in tea, mediating their antidepressant effects. A major pathway was found to be the ERK/CREB/BDNF signaling pathway, up-regulated by a number of compounds in tea including teasaponin, L-theanine, EGCG and combinations of tea catechins and their metabolites. Black tea theaflavins and EGCG are potent anti-inflammatory agents via down-regulation of NF-κB signaling. Multiple compounds in tea are effective modulators of dopaminergic activity and the gut-brain axis. Taken together, our findings show that constituents found in all major tea types, predominantly L-theanine, polyphenols and polyphenol metabolites, are capable of functioning through multiple pathways simultaneously to collectively reduce the risk of depression.
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The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise.
Juszkiewicz, A, Glapa, A, Basta, P, Petriczko, E, Żołnowski, K, Machaliński, B, Trzeciak, J, Łuczkowska, K, Skarpańska-Stejnborn, A
Journal of the International Society of Sports Nutrition. 2019;16(1):7
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According to previous studies, strenuous exercise may contribute towards an imbalance in Th1/Th2 cytokines that are secreted by the immune system, resulting in an impairment of the immune system. The main aim of this study was to analyse the effect of L-theanine on cytokines of the immune system and establish the role of L-Theanine as immunomodulatory. This double blind randomised study recruited 20 men from the Polish rowing team. The subjects were randomised to the supplemented group and placebo group. The supplemented group received gelatine capsules with 150 mg L-theanine extract whilst the placebo group received visually identical capsules with corn starch. The participants in the study were asked to take two capsules per day for 6 weeks. Athletes from both the groups did not differ significantly in terms of their mean age, body height, body weight and years of training. After 24 hour recovery, the athletes in the supplemented group showed lower amount of cytotoxic cell. The authors concluded based on the study that supplementation with L- theanine in athletes exposed to strenuous exercise had beneficial effect.
Abstract
BACKGROUND The aim of this study was to analyze the response of selected components of the immune system in rowers to maximal physical exercise, and to verify if this response could be modulated by supplementation with L-theanine. METHOD The double-blind study included 20 members of the Polish Rowing Team. The subjects were randomly assigned to the supplemented group (n = 10), receiving 150 mg of L-theanine extract for 6 weeks, or to the placebo group (n = 10). The participants performed a 2000-m test on a rowing ergometer at the beginning (1st examination) and at the end of the supplementation period (2nd examination). Blood samples were obtained from the antecubital vein before each exercise test, 1 min after completing the test, and after a 24-h recovery. Subpopulations of T regulatory lymphocytes (Tregs) (CD4+/CD25+/CD127-), cytotoxic lymphocytes (CTLs) (CD8+/TCRαβ+), natural killer (NK) cells (CD3-/CD16+/CD56+) and TCRδγ-positive (Tδγ) cells were determined by means of flow cytometry. The levels of interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 10 (IL-10), interferon gamma (INF-ɤ) and total antioxidant capacity (TAC) were determined with commercially available diagnostic kits. RESULTS Supplementation with L-theanine contributed to a significant post-exercise decrease in IL-10 concentration, which was reflected by higher values of IL-2 to IL-10 and IFN-γ to IL-10 ratios. Moreover, a significant post-recovery decrease in CTL count, Treg to NK and Treg to CTL ratios was observed in the supplemented group. CONCLUSION Despite the decrease in the number of some cytotoxic cells (CTLs) and an increase in the proportion of Tregs to CTLs, supplementation with LTE seems to exert a beneficial effect on a disrupted Th1/Th2 balance in elite athletes, as shown by the decrease in IL-10 concentration.