Impact of Gastric pH and Dietary Fiber on Calcium Availability of Various Calcium Salts

Abstract

The objective of this study was to compare calcium release and ionization from commercialcalcium supplements and various salts of calcium with different solubilities. The impact of pH of testfluid and dietary fiber co-administered with calcium supplement on calcium availability was alsostudied. Compressed tablets of six different calcium salts were prepared by direct compression.Calcium release from tablets was tested in simulated gastric fluid without pepsin (SGF, pH 1.2) or fedstate simulated gastric fluid (FSSGF, pH 4.8), using USP dissolution apparatus. The ionized calciumconcentration in test fluid was determined by calcium ion selective electrode. The results demonstratedthat most of the formulations released calcium within 1 hour. Tablets made of higher solubilitycalcium salts demonstrated a faster calcium release. The calcium release from calcium hydrogenphosphate and calcium carbonate tablets in gastric fluid with higher pH showed a slower calciumrelease than in SGF. The dietary fiber co-administered with calcium supplement influenced thecalcium availability, especially in medium with higher pH. The results suggested that most of thecalcium salts could be used as calcium supplement. However, the use of calcium carbonate required anacidic environment in order to be dissolved in the gastrointestinal tract. Key Words: Calcium; Tablet; Gastric pH; Pectin; Dietary fiber