Bestimmung der Verfügbarkeit von Calciumsalzen in vitro

The potential availability for absorption of calcium present in 4 calcium salts (gluconate, carbonate, tricalcium phosphate and dicalcium phosphate) was determined in vitro in a system which mimics the conditions in the gastrointestinal tract. Dialysable calcium was regarded as potentially available. At pH values of 7.0-7.2, more than 80°% of the calcium in solutions of pure calcium gluconate, calcium carhonate, tricalcium phosphate, and 45% of calcium in dicalcium phosphate were dialysable. Increasing pH decreased dialysable calcium to different degrees, dependent on the single salts. Addition of foods (mixed diet, spinach, wheat bran) at pH 7.1 decreased dialysable calcium in gluconate, carbonate, tricalcium phosphate, but had a comparatively small effect in the case of dicalcium phosphate.