A Randomized, Double-Blind Comparison Study of Royal Jelly to Augment Vascular Endothelial Function in Healthy Volunteers

Aims: Royal jelly, a creamy substance secreted by honeybees, has been reported to have beneficial effects against dyslipidemia and metabolic syndrome. However, the effects of royal jelly on atherogenesis remain unknown. Hence, we prospectively evaluated whether royal jelly augments vascular endothelial function, which can reflect early atherogenesis, in healthy volunteers. Methods: This was a single-center, double-blind, 1:1 randomized placebo-controlled study conducted from October 2018 to December 2019. A total of 100 healthy volunteers were randomly assigned to receive either royal jelly 690 mg or placebo daily for 4 weeks. The primary endpoint was augmentation in vascular endothelial function as assessed using the change in the reactive hyperemia peripheral arterial tonometry index (RH-PAT) index, and the secondary endpoints were the changes in liver function and lipid profiles between baseline and 4 weeks after enrollment. Results: The mean age of the participants was 35.0±9.3 years in the placebo group and 36.1±9.1 years in the royal jelly groups; 45% and 50% of the placebo and the royal jelly groups, respectively, were male. The percentage relative change in the RH-PAT index was significantly higher in the royal jelly group than in the placebo group (21.4%±53.1% vs. 0.05%±40.9%,P=0.037). The percentage relative changes in alanine aminotransferase and γ-glutamyl transpeptidase were significantly lower in the royal jelly group than in the placebo group (alanine aminotransferase: −6.06%±22.2% vs. 11.6%±46.5%,P=0.02; γ-glutamyl transpeptidase: −3.45%±17.8% vs. 4.62%±19.4%,P=0.045). Lipid profiles were not significantly different between the two groups. Conclusions: Royal jelly might have antiatherogenic property by improving vascular endothelial function. It also augmented liver functions in healthy volunteers.