Royal Jelly Supplementation Improves Endurance and Mitochondrial Biogenesis in Athletes: A Crossover Trial

Royal jelly (RJ) has been shown in animal models to alleviate muscle fatigue and damage during exercise. This trial was designed to assess the effect of RJ on exercise performance, oxidative stress, and nuclear factor erythroid 2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression in endurance-trained male athletes. In this randomized, crossover trial, 18 eligible participants were randomly assigned to receive RJ (1000 mg/day) in one period and placebo in another period for 2 weeks, with a 2-week washout. The exhaustive endurance-running test was conducted to assess time to exhaustion (TTE), perceived exertion, arousal levels, and affective response. Blood samples were collected to assess gene expression, malondialdehyde (MDA), total antioxidant capacity (TAC), and total oxidant status (TOS). The carryover and sequence effects were not significant for all outcomes (p-value > 0.05). The mean changes from baseline were statistically significant for TTE (7.32; 95% CI: 4.61-10.02; p-value: 0.001), post-exercise TOS (-18.56; 95% CI: -31.61 to -5.51; p-value: 0.008), and PGC-1α expression (2.23; 95% CI: 0.49-3.98; p-value: 0.015) with RJ, and TTE (2.69; 95% CI: 0.80-4.59; p-value: 0.008) with placebo. The treatment differences in TTE and PGC-1α expression relative to placebo were 4.63 min (95% CI: 1.78-7.48; p-value: 0.002) and 2.12 (95% CI: 0.16-4.09; p-value: 0.035), respectively. No significant effects were observed in Nrf2 expression, perceived exertion, arousal levels, affective response, heart rate, and other oxidative stress markers. RJ supplementation improved endurance capacity and PGC-1α expression but had no significant effect on oxidative stress and Nrf2 expression in endurance-trained athletes, suggesting selective ergogenic effects. Further studies are needed to evaluate its efficacy across different athlete populations.