Eggshell is primarily composed of calcium carbonate, which is a bioavailable form of calcium. Calcium supplementation is a well-established intervention for osteoporosis, a condition characterized by decreased bone mineral density and increased fracture risk. Several studies have investigated the use of eggshell powder as a natural calcium source. Clinical trials and in vitro research have shown that eggshell calcium is as effective, or in some cases more effective, than purified calcium carbonate in supporting bone metabolism and improving bone mineral density, particularly in postmenopausal women. Additionally, eggshell powder often contains trace amounts of other minerals such as strontium and magnesium, which may further contribute to bone health.

A notable study published in the journal International Journal of Clinical Pharmacology Research (1999) demonstrated that supplementation with eggshell powder improved bone mineral density in postmenopausal women with osteoporosis. Other research has confirmed the good bioavailability of eggshell-derived calcium, suggesting it is a suitable dietary supplement. However, the body of evidence is moderate and most studies are relatively small; large-scale randomized controlled trials are lacking. The use of eggshell as a treatment for osteoporosis is thus supported by scientific rationale and some preliminary clinical data, but it does not yet have the same level of evidence as standard pharmaceutical interventions.