Requirements: The RDA for phosphorus is the same as that for calcium, 800 mg. for adults. However, the average dietary intake of calcium is low, at about 500 mg.; that for phosphorus is more like 1,500 mg. In pregnancy and lactation, as well as in children aged 11-18, the RDA is higher, at 1,200 mg. If the phosphorus intake is high or body levels are increased, we may need to take more calcium to achieve the desired 1:1 ratio to maintain biochemical homeostasis.

Phosphorus in small amounts like 100-200 mg. is often contained in multimineral or multivitamin formulas. It is unlikely that anyone takes phosphorus as a separate supplement.