Egg yolk hydrolysate shows moderate impact on osteoporosis in ovariectomized rats

BACKGROUND: This study investigated the protective effect of egg yolk hydrolysate (FC) on osteoporosis in ovariectomized (OVX) rats, a well-established model of postmenopausal bone loss. OVX rats were fed diets supplemented with 0.2% or 1% FC for 13 weeks. The regulatory effects were evaluated by measuring bone mineral density (BMD) and microarchitecture using computed tomography, analyzing serum bone remodeling biomarkers, and examining osteoclast differentiation and resorption activity in isolated bone marrow cells. Western blotting was used to evaluate the expression of key osteoclastogenic proteins. RESULTS: FC 1% supplementation significantly improved trabecular BMD and percentage bone volume in OVX rats. Treatment with FC 1% also significantly increased serum osteocalcin levels (P = 0.028). Furthermore, FC 1% significantly reduced osteoclast differentiation (decreased tartrate-resistant acid phosphatase-positive area by approximately 49%, P < 0.05) and bone resorption activity. At the molecular level, FC 1% significantly decreased cellular Fos (c-Fos) expression, whereas other osteoclastogenic proteins, including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), cathepsin K and matrix metalloproteinase 9 (MMP-9), showed non-significant downward trends. CONCLUSION: These findings indicate that FC exerts moderate protective effects against bone loss in OVX rats by simultaneously suppressing osteoclast activity and enhancing bone formation. These results support the potential of egg yolk hydrolysate as a functional food ingredient for osteoporosis management, particularly in postmenopausal women. Further investigations are needed to fully understand the underlying mechanisms and assess long-term efficacy. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.