BIOAVAILABILITY OF CALCIUM FROM BOVINE-BONE-MARROW CALCIUM (BBMCA) AND CALCIUM-CARBONATE IN VITAMIN-D-DEFICIENT RATS

Bovine-bone-marrow calcium (BBMCa) has been widely used for the enrichment of Ca in foods. However, its biological availability in humans and animals has not yet been fully clarified. We have therefore investigated the bioavailability of Ca from unsterilized BBMCa (UBBMCa), sterilized BBMCa (SBBMCa) (both of which are commercially available), and Ca carbonate as a control compound. Vitamin D-deficient rats were used to examine the Ca bioavailability of the BBMCa, these being unaffected by the vitamin D nutritional status in the animals. Vitamin-D-deficient rats were fed ad libitum a vitamin D-free 1-20% Ca diet prepared by using UBBMCa, SBBMCa, or Ca carbonate as Ca sources for 28 days. Body weight plasma Ca level, and alkaline-phosphatase activity (Alp) of the rats were measured periodically. The femoral-bone-mineral density and biomechanical strength of the rats were also measured after the feeding period. The UBBMCa and SBBMCa groups showed a rapid increase in plasma-Ca level to the normal range and an increase in bone-ash weight, bone-mineral density, and biomechanical strength, the values of which were significantly higher than those in the Ca carbonate group. The bioavailability of Ca from UBBMCa was substantially equal to that from SBBMCa in increasing plasma Ca level, bone-mineral density, and bone biomechanical strength. These findings suggest that the bioavailability of Ca from UBBMCa and SBBMCa is much higher than that of Ca carbonate in the vitamin D-deficient state, and they are available as Ca sources for the enrichment of Ca in food.