Intestinal absorption of calcium from three commerical calcium preparations in man

Intestinal 47Ca absorption was determined from blood and stool radioactivity after oral administration of 150 ml saline containing the isotope (as 47CaCl2) and 500 mg of elementary calcium in the form of one of three commercial calcium preparations from "NAF" or "Collett" (containing calcium carbonate) or from "Sandoz" (containing mainly calcium lactogluconate). 51CrEDTA was used as unabsorbable marker to allow corrections for incomplete faecal collection. The calcium carbonate preparations were only partially dissolved when administered, but the calcium absorption from these preparations was found to be no less than that from the completely soluble calcium "Sandoz" preparation. The calculated minimal absorption of calcium was, on an average, about 100 mg from all three calcium preparations in subjects without known intestinal calcium absorption defects.