Enhancement of Interferon-γ Secretion by <i>Lepidium meyenii</i> Extract Supplementation After Exhaustive Endurance Exercise in Healthy Men: A Double-blind, Placebo-controlled Trial

<b>Aim:</b> To investigate the effects of 12-week <i>Lepidium Meyenii</i> extract supplementation on immune responses and inflammatory cytokines after exhaustive endurance exercise (EEE), emphasizing its novel focus on peripheral blood mononuclear cells (PBMCs) cytokine secretion and the implications of interferon-γ (IFN-γ) as a marker for immune modulation. <b>Methods:</b> Twenty healthy men were recruited and assigned into maca and placebo groups using a matched-pair design based on their maximal oxygen consumption (V̇O_2max). All participants consumed 2.25 g of maca or placebo twice per day for 12 weeks, and they then performed EEE. Researchers collected blood samples before exercise, immediately after exercise, and at 2, 4, and 24 hours post-exercise to analyze immune functions and inflammatory markers. <b>Results:</b> No significant differences were observed in the variables between the two groups before supplementation. However, interferon-γ levels from peripheral blood mononuclear cells were significantly higher in the maca group than in the placebo group immediately and at 24 hours after exercise. Regarding the main time effect, the number of lymphocytes in all participants was significantly lower at 2 and 4 hours after exercise than before supplementation. The CD4⁺/CD8⁺ ratio in the groups was significantly lower immediately after exercise than before supplementation, and the ratio retuned to baseline levels at 2 hours after exercise. <b>Conclusion:</b> A 60-minute EEE session induces the open window phenomenon, characterized by immune suppression. Moreover, 12-week maca supplementation had positive effects only on interferon-γ levels from peripheral blood mononuclear cells.