Intestinal calcium absorption from different calcium preparations: Influence of anion and solubility

Abstract

Not only is the calcium content of a preparation significant for providing adequate calcium supplementation for the prophylaxis and therapy of osteoporosis, but also its bioavailability is of essential importance. In the present study, the bioavailability of calcium citrate and calcium lactogluconate/carbonate from a therapeutic dose (= 500 mg Ca2+) was compared in men aged between 45 and 60 years on an intra-individual basis. Calcium citrate was administered both as a solution and as a suspension to 18 healthy volunteers. Using a double-isotope method, the intestinal absorption from the three preparations was determined in randomized order at intervals of 2-4 weeks. The stable isotope 44Ca (20 mg), in highly enriched form, was added in each case to the ready-to-drink solutions and, at the same time, a sterile and pyrogen-free solution containing 5 mg of the stable isotope 42Ca was injected intravenously. The intestinal calcium absorption was then determined after 24 h on the basis of the ratio of the two isotopes in the plasma. There was a significantly higher absorption of 29% from the citrate solution than from the lactogluconate/carbonate solution (25%). Absorption from the citrate suspension was similar to that from the lactogluconate/carbonate solution. While no correlation was found between the measured values for calcium absorption from the three preparations and the plasma concentration of 1,25-dihydroxycholecalciferol, significant inverse correlations with the basal parathyroid hormone concentration were observed for the citrate and lactogluconate/ carbonate solution. The results of this study show that quantitative data on intestinal calcium absorption can be obtained without employing radioactive isotopes in humans. Moreover, they show that calcium absorption is not determined only by the solubility and the degree of ionization of the calcium salt administered, but rather that it is of a complex nature.

Calcium Bioavailability and Parathyroid Hormone Acute Changes after Oral Intake of Dairy and Nondairy Products in Healthy Volunteers

“…Calcium carbonate, on the other hand, was shown to be absorbed differently depending on the simultaneous administration of a meal [15]. Furthermore, Hansen and colleagues [21] have recently suggested a positive direct effect of the citrate ions per se on passive (3) LM induced a significant decrease only during the first 2 h (p<0.01), tending to stay low at t3 (p<0.1) and to return to baseline at t4 (p=NS). Comparison of the area under the curve (AUC) for iPTH showed that: (1) after PM intake iPTH AUC was 27% larger than that after YO (p<0.05), 31% larger than that after CC (p<0.05) and 45% larger than that after LM (p<0.001); (2) after YO/CC intake iPTH the AUC values were similar (p=NS) and 20% larger than after LM (p<0.05).…”

“…We can assume that the better performance of PM may be due to its calcium citrate content since several authors [14][15][16][17][18][19][20][21] have reported a significantly higher bioavailability for calcium citrate than for other calcium salts; however, others disagree [22]. Calcium citrate supplements have been shown to induce a significantly larger serum calcium increase [14][15][16][17] and a significantly greater PTH suppression [18,19] than other calcium salts regardless of the method of administration, i.e., with or without a meal.…”

Use of eggshells as a raw material for production of calcium preparations

“…Calcium carbonate is soluble practically only in a strongly acidic medium, and calcium citrate is well soluble in neutral and alkaline media, which affects the availability of the latter salt especially in the upper sections of the small intestine (for example in the duodenum, pH = 7). It is also worth mentioning that calcium is absorbed in the alimentary tract in ionised form and a higher dissociation constant of calcium citrate compared to the carbonate may explain the greater bioavailability of the salt (Hansen et al 1996). An additional advantage of calcium citrate compared to calcium carbonate is that the carbonate is poorly absorbed in patients with stomach hypoacidity.…”

Assessing Micronutrient Adherence after Bariatric Surgery: An Exploratory Study

“…The preference for citrate is also likely associated with the impression that calcium citrate is better absorbed than calcium carbonate. However, clinical studies have not consistently demonstrated that calcium carbonate is inferior to calcium citrate with regard to oral bioavailability and long-term outcomes [14][15][16][17][18][19][20][21][22]. In a randomized, double-blind, crossover trial aimed to compare the absorption kinetics between calcium citrate and calcium carbonate (both provided 500 mg of elemental calcium with 125 international units of vitamin D) in 18 patients with RYGB approximately 2 years prior (range 11 -35 months), calcium citrate appeared to result in a statistically significantly higher serum calcium exposure within 6 hours of dose administration compared with calcium carbonate (6-hour area under the concentration-time curve…”