Bones

Bone is living tissue in constant turnover — osteoblasts building, osteoclasts dissolving — and the balance is nutrient-governed. Calcium is the raw mineral, but it's useless without the directors: vitamin D drives calcium absorption from the gut, and vitamin K activates the proteins (osteocalcin) that lay that calcium into bone instead of soft tissue. Magnesium, phosphorus, and manganese build out the crystal matrix; vitamin C makes the collagen scaffold the minerals attach to. The whole system is silent until a fracture — which is exactly why the inputs matter for decades before any symptom appears.