Abstract
Although many kinds of calcium compounds are available commercially, the truly active compounds that are easily dissolved by digestive fluids and contribute to the prevention of osteoporosis have not been determined. We therefore measured the solubility of Ca compounds in artificial gastric and intestinal juice. The solubility of each Ca compound in artificial gastric juice was almost 100%, but the solubility in artificial intestinal juice showed the order: Ca lactate (14.2%) >Ca citrate (13.9%) >Ca gluconate (9.33%) >Ca glycerophosphate (4.70%) >Ca phosphate (4.38%) >Ca oxide (1.64%) >Ca carbonate (0.19%). Addition of human saliva to Ca gluconate increased its solubility in artificial intestinal juice, while addition of mucin to the Ca compounds also increased the solubility as follows: Ca gluconate (84.0%) > Ca citrate (61.7%) >Ca phosphate (52.7%) > Ca lactate (36.0%) >Ca glycerophosphate (25.4%) >Ca carbonate (23.8%) >Ca oxide (3.02%). In in vivo experiments with mice, addition of mucin to Ca compounds in the diet increased the percentage of Ca in the tibia from 6.02% to 8.45%, the breaking force of the tibia (g/mmm2) from 650 to 953, and the bone strength of the tibia (×107dyn) from 6.03 for non-treated mice to 9.97.
