Dietary intake of antioxidants and aerobic capacity among Collegiate and Masters athletes: a cross-sectional study

Background Effects of exogenous dietary antioxidants on endurance performance remain largely uncertain. Purpose We evaluated dietary antioxidant intakes and aerobic capacity among female and male Collegiate and Masters athletes. Methods In this cross-sectional study, we assessed the dietary intakes of vitamins A, C and E, glutathione, lutein–zeaxanthin, and their relationship with aerobic capacity among Collegiate and Masters Athletes. Dietary intake was measured using food frequency questionnaire. Aerobic fitness was assessed by maximal oxygen consumption (VO 2 max). Results 135 Collegiate and Masters athletes (71 women; 64 men, 35.9 ± 12.1 years of age) were included in the study. Collegiate male athletes had significantly greater total glutathione intake (55.7 ± 18.8 vs. 38.3 ± 13.7 mg/day, p = 0.011) and maximal oxygen consumption (VO 2 max) (48.4 ± 9.7 vs. 39.2 ± 3.9 mL/kg/min, p = 0.005) compared to Collegiate female athletes. Similarly, Masters male athletes had significantly greater total glutathione intake (48.6 ± 18.9 vs. 40.5 ± 16.5 mg/day, p = 0.022) and VO 2 max (43.4 ± 10.2 vs. 35.8 ± 8.7 mL/kg/min, p < 0.001) compared to Masters female athletes. Masters female athletes had significantly higher lutein–zeaxanthin intake (8,344.9 ± 5,659.1 vs. 6,015.8 ± 5,707.5 mcg/day, p = 0.043) compared to Masters male athletes. Glutathione ( r = 0.53, p = 0.002), vitamin A ( r = 0.38, p = 0.032), and vitamin C intake ( r = 0.35, p < 0.05) were positively correlated with VO 2 max among Collegiate athletes. For Masters athletes, VO 2 max was positively correlated with glutathione intake ( r = 0.23, p = 0.019). In regression models, dietary glutathione intake was significantly associated with VO 2 max in Model 1 ( B = 0.257 ± 0.082, p = 0.002) and Model 2 ( B = 0.163 ± 0.081, p = 0.047), but not in Model 3 ( B = 0.053 ± 0.087, p = 0.542). Conclusion Dietary glutathione intake was positively associated with aerobic capacity in unadjusted models; this relationship was fully attenuated after controlling for sex, age, and energy intake. These data suggest that glutathione intake may serve as a proxy marker for a comprehensive, high-quality dietary pattern rather than an independent physiological driver of fitness.