Effect of single large doses of oral calcium on serum calcium levels in the young and the elderly

Abstract

Single large oral doses of calcium carbonate containing 4 g elementary calcium caused a mean peak rise in serum Ca of 1.47 mg 100 ml at 2 hr in six young volunteers (mean age, 28 yr) in the fasting state. A 4-g load taken with breakfast produced a higher mean peak value ( 11.77 mg 100 ml ), with hypercalcemia sustained for 2 hr. In six healthy elderly subjects (mean age, 81 yr) the mean rise in serum calcium after 4 g of oral calcium was 1.26 mg 100 ml . One week after pretreatment with an injection of 400,000 U of calciferol the fasting level was 1 mg 100 ml higher and the mean rise after loading was 1.7 mg 100 ml , with hypercalcemia sustained for 3 hr. In another group of five elderly subjects a 4-g calcium load produced a rise in serum calcium of only 0.69 mg 100 ml , but after 1 wk of pretreatment with 5000 units calciferol daily, the same load led to a rise of 1.39 mg 100 ml . We hope that orally induced hypercalcemia in conjunction with physiologic calciferol supplementation may be of benefit in the treatment of osteoporosis comparable to that obtained by calcium infusions. We also suggest that some elderly people even in sunny climates may suffer from subclinical vitamin D deficiency. These postulates need further investigation.