The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise

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.

Impairment between Oxidant and Antioxidant Systems: Short- and Long-term Implications for Athletes’ Health

“…Furthermore, one crossover experimental trial showed how GTE supplementation might have a potential in preventing physical activity induced oxidative stress without compromising endogenous antioxidant mechanisms. However, GTE supplementation does not prevent exercise induced muscle damage, nor improve performance, but supplementation with L-theanine, the main amino acid present in tea leaves, contributed to a significant post-exercise decrease in inflammation parameters such as IL-2, IL-10, and interferon (IFN)-γ and an improvement in the disturbed immune response in elite athletes [102,110]. Moreover, supplementation with GTE (500 mg/day) for 15 days in sixteen trained male amateur athletes showed an improvement in muscle damage and oxidative stress in response to fatigue as well as positive effects on neuromuscular function in response to a cumulative fatigue condition [111].…”

Effect of Tea Polyphenol on Serum Hormone, Serum Enzyme Activity and Antioxidant-Related Gene Expression in Chinese Yellow Chicken under Heat Stress

“…Tea polyphenol can also prevent atherosclerosis [21]. Studies have shown that L-theanine in tea can regulate immunity, regulate the secretion of Th1 and Th2 cytokines, and supplement L-theanine can increase serum interleukin-2 (IL-2) and interferon gamma (IFN-γ) content [22]. However, there are few reports on the supplementation of tea polyphenols as feed additives to improve antioxidant properties and immune functions in animals, especially in relieving heated-stress states.…”

L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications

“…In another study, it was found that L-theanine antagonized cannabinoid receptor 1 and inhibited its activity, relieved the inhibition of cannabinoid receptor 1 on COX-2 expression, reduced the pro-inflammatory factor TNF-α, and enhanced the anti-inflammatory factor IL-10, making L-theanine show a significant regulatory effect on the immune function of normal and E44813-stressed rats ( 97 ). Additionally, in the study of Polish rowing team members, it was found that L-theanine supplementation could contribute to the reduction of IL-10 concentration after exercise, which had an advantageous influence on the destruction of Th1/Th2 balance of top athletes ( 98 ).…”