Members of the Polish Rowing Team taking L-theanine supplements were found to have improvements in the ratio of T helper type 1 (Th1)/T helper type 2 (Th2) cells, cells that play an important role in the immune system, according to data published in the Journal of the International Society of Sports Nutrition.
However, L-theanine supplementation was also associated with increases in levels of pro-inflammatory markers and decreases in cytotoxic lymphocytes (CTLs: immune cells that destroy damaged or defective cells) and the anti-inflammatory cytokine, interleukin-10, report scientists from the Faculty of Physical Culture in Gorzów Wielkopolski and Pomeranian Medical University.
“To the best of our knowledge, this was the first study to analyze the effect of L-theanine on selected cytotoxic cells, Treg and some Th1 and Th2 cytokines in elite athletes exposed to strenuous exercise,” they wrote.
“[…[] despite a decrease in CTL and unfavorable increase in Treg ratio to some cytotoxic cells, some elements of cellular immunity might be enhanced due to inhibition of IL-10 synthesis and a beneficial shift toward production of Th1 cytokines.
“Thus, it can be stipulated that despite the decrease in the number of some cytotoxic cells (CTLs) and an increase in the proportion of Tregs to CTLs observed after the supplementation, LTE may exert a beneficial effect on a disrupted Th1/Th2 balance, as shown by the decrease in IL-10 concentration.
“The decrease in IL-10 level, occurring regardless of higher TAC, might be a reason behind the post-recover increase in granulocyte percentage in the supplemented group.”
Study details
The double-blind, placebo-controlled randomized trial involved 20 members of the Polish national rowing team who were randomly assigned to receive placebo or 150 mg per day of L-theanine for six week during strenuous training.
Results showed that participants in the L-theanine group experienced significant post-exercise decreases in IL-10 concentration and increases in ratios of IL-2 to IL-10 and IFN-gamma to IL-10.
In addition, significant post-recovery decreases were observed for CTL count, and ratios of Treg to NK and Treg to CTL for the L-theanine group.
“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,” concluded the researchers.
Source: Journal of the International Society of Sports Nutrition
February 2019, 16(1):7. doi: 10.1186/s12970-019-0274-y
“The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise”
Authors: A. Juszkiewicz et al.