Biological Importance of Magnesium and Calcium

The average adult body contains roughly 25 g of magnesium and about 1200 g of calcium — again dwarfing the 5 g of iron and 0.06 g of copper the body carries — and the recommended daily intake of these elements runs to 200–300 mg.

Magnesium is indispensable to metabolism because every enzyme that uses ATP for phosphate transfer requires it as a cofactor, and it also sits at the centre of chlorophyll, the pigment plants use to capture light for photosynthesis.

Calcium, meanwhile, is overwhelmingly a structural element: roughly 99% of the body's calcium is locked up in bone and teeth. The small remainder is nonetheless functionally critical, involved in neuromuscular signalling, transmission between neurons, maintaining cell-membrane integrity, and blood clotting; its concentration in blood plasma is tightly held at about 100 mg L⁻¹, regulated by the two hormones calcitonin and parathyroid hormone. Bone itself is far from an inert scaffold — it …