Royal jelly does not prevent bone loss but improves bone strength in ovariectomized rats

Objective: Royal jelly (RJ) has been used for medical and nutritional purposes, and previous studies have indicated that it may have estrogenic activity. The present study investigated the effects of RJ on bone metabolism in ovariectomized (OVX) rats. Methods: Rats (12 weeks old) were randomly divided into four groups, namely Baseline, Sham, OVX, and OVX + RJ groups. Rats in the Baseline group were killed immediately, whereas rats in the OVX and OVX + RJ groups underwent bilateral ovariectomy and those in the Sham group underwent sham operation. RJ was administered to rats in the OVX + RJ group daily for 12 weeks. At the end of the 12-week period, bone mass, bone histomorphometry, and bone mechanics were analyzed. Results: Femur bone mineral density (BMD) was significantly lower in the OVX group than in the Sham group, and this decrease in BMD was not ameliorated by RJ administration. However, femur stiffness, as evaluated by a three-point bending test, was significantly higher in the OVX + RJ group than in the OVX group. Conclusion: The findings of the present study suggest that RJ does not prevent bone loss, but does improve bone strength in OVX rats.