What is the normal calcium balance
Calcium balance represents the net difference between calcium intake and output in the body in steady state. This balance is positive during skeletal growth in children, zero in adults, and negative in the elderly.
In a healthy adult on an average Western diet of 1000 mg elemental calcium per day, the net intestinal calcium absorption is ∼200 mg; bone mineral accretion (∼500 mg) equals bone resorption (∼500 mg). The kidneys, under hormonal control, will excrete ∼200 mg calcium in the final urine, rendering a neutral calcium balance. Calcium homeostasis and balance become altered in advanced chronic kidney disease (CKD). A positive calcium balance has been demonstrated in patients with CKD stage 3 and 4 placed either on a 2000 mg calcium diet or on 1500 mg calcium carbonate supplements. Thus calcium supplementation in this population should be used with caution, to avoid calcium overload.