Modulation of Redox and Immune Responses Following Eight Weeks of Supplementation with a Yeast Cell-Derived...

Background/Objectives: Nutritional strategies targeting redox and immune pathways may help to stabilize redox hemodynamics and support immune competence. Controlled physiological stress models allow examination of how nutrients influence dynamic antioxidant and inflammatory responses. Methods: In this randomized, double-blind, placebo-controlled trial (RCT), 39 healthy, moderately active men (supplement group: n = 20; placebo group: n = 19) received a yeast cell-derived formulation containing β-glucans and micronutrients or placebo for 8 weeks. Two standardized high-intensity interval training (HIIT) sessions (PRE/POST) transiently induced oxidative and inflammatory stress. Outcomes included reactive oxygen species (ROS; whole-blood EPR), total antioxidant capacity (FRAP), superoxide dismutase (SOD), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and upper respiratory tract infection (URTI) incidence and duration. Results: Prior to the intervention period, acute supplement intake resulted in a more pronounced reduction in ROS from 0' to 60' compared with placebo (-6.2%; p ≈ 0.14). After eight weeks, fasting FRAP increased only in the supplemented group (p < 0.01). Mixed-model repeated-measures ANOVA demonstrated significant time × group interactions for FRAP in both PRE and POST assessments, indicating differential temporal trajectories. The chronic FRAP increase correlated with the acute ROS reduction (p < 0.05; r² = 0.21). SOD activity was higher in the supplemented group at 60' in the POST assessment (p < 0.05), and a significant time × group interaction was observed for SOD in POST. TNF-α decreased across the intervention in participants with elevated baseline values, whereas individuals with low initial concentrations showed no change. The supplemented group reported shorter URTI duration (-1.4 days; d = 0.34) and fewer prolonged episodes (>10 days: 5% vs. 15.8%), although these differences were not statistically significant. Conclusions: Eight weeks of supplementation with a yeast cell-derived formulation containing β-glucans and micronutrients was associated with differences in selected redox-related markers, including FRAP and SOD, without altering exercise-induced ROS dynamics. The observed patterns suggest subtle modifications in antioxidant-related response characteristics under standardized physiological stress. These findings warrant further investigation in larger and more heterogeneous cohorts, particularly in populations exposed to higher oxidative or inflammatory burden.