The use of shell (typically oyster shell or eggshell) as a remedy for calcium deficiency is primarily supported by scientific evidence due to its high calcium carbonate content. Shells, especially those from oysters and eggs, consist mostly of calcium carbonate, which is a common source of supplemental calcium in both traditional and modern medicine. Numerous studies have evaluated the bioavailability and safety of calcium derived from shells. For example, research has shown that oyster shell calcium is absorbed comparably to standard calcium carbonate supplements and can effectively raise serum calcium levels in individuals with deficiency. However, shells must be properly processed to remove contaminants and ensure safety for human consumption.

In traditional medicine, the use of shells for treating bone weakness and related symptoms has been documented in systems such as Traditional Chinese Medicine (where oyster shell, or "Mu Li," is sometimes used), but the modern rationale is largely based on the elemental composition and clinical supplementation studies. That said, while shell calcium is effective as a calcium supplement, the overall clinical evidence for its superiority to other forms of calcium is limited. Safety concerns regarding heavy metal contamination (e.g., lead) have also been raised, emphasizing the need for quality control. Overall, the practice is scientifically justified for addressing calcium deficiency, provided that the shells are processed appropriately.