Effects of Eggshell Calcium- and Vitamin D-Fortified HMR Combined with Aerobic Exercise on Bone Mineral Density in Postmenopausal Women: A Pilot Randomized Controlled Trial

Background/Objectives: Adequate calcium and vitamin D intake, along with regular physical activity, is essential for maintaining skeletal health in postmenopausal women. In populations with low dairy consumption, sustainable and bioavailable calcium sources are required to support bone integrity. Eggshell powder offers a highly bioavailable, eco-friendly, and cost-effective calcium source consistent with environmental sustainability goals. This pilot randomized, double-blind, controlled trial investigated the effects of calcium- and vitamin D-fortified home meal replacements (HMRs) made with eggshell powder, combined with weight-bearing aerobic exercise, on bone mineral density (BMD) and bone turnover markers in postmenopausal women. Methods: Thirty-six women aged 50–59 years were randomly assigned (1:2 ratio) to a control group (regular HMR) or an intervention group (HMR fortified with 418 mg eggshell-derived calcium and 837 IU vitamin D). Participants consumed one HMR daily, five days per week, and were encouraged to engage in weight-bearing aerobic exercise for 30–60 min, five times weekly, over six months. Results: High adherence was observed for both dietary (94%) and exercise regimens. No significant differences were found between groups in overall BMD or bone metabolic markers after six months. Exploratory post hoc subgroup analysis suggested possible exercise–nutrition interactions in lumbar spine BMD. Conclusions: No significant overall BMD effect was found. Fortified HMRs achieved excellent adherence and corrected nutrient deficiencies, demonstrating feasibility. Future large-scale trials with adequate power based on realistic effect sizes are warranted to evaluate reproducibility of these exploratory findings.