Dermal, intestinal, and renal obligatory losses of calcium: relation to skeletal calcium loss.

Calcium balance is the difference between dietary calcium intake on the one hand and dermal, fecal, and urinary losses on the other. Bone is lost throughout adult life by at least three different mechanisms. Whether all these processes are affected by dietary calcium is at present unknown. In case they are not, dietary calcium intake should balance an adjusted value estimated as obligatory skeletal calcium loss minus obligatory external (dermal + intestinal + urinary) calcium loss. Such a correction would reduce estimated calcium allowances. To solve this question it is important, however, to ascertain whether obligatory bone loss is affected by dietary intake of calcium, ie, Can a high dietary calcium or calcium supplementation influence bone metabolism and reduce bone loss at all ages?