title: Effect of estrogen treatment and vitamin D status on differing bioavailabilities of calcium carbonate and calcium citrate.
abstract: The authors hypothesized that estrogen treatment or vitamin D status may affect the bioavailability of two common calcium supplements differently. Using data derived from a recent trial in 25 postmenopausal women, the authors found that deltaAUC of serum calcium after subtraction of placebo was significantly higher after calcium citrate (median, 0.85; 25th to 75th percentile, 0.70 to 3.15) than after calcium carbonate (0.25; -0.58 to 1.00) in non-estrogen-treated patients. There was no difference in the bioavailability of calcium between the two calcium formulations in estrogen-treated patients. Bioavailability was also significantly higher with the citrate salt for the subgroups with lower serum 25-hydroxyvitamin D and higher serum 1,25-dihydroxyvitamin D concentrations. In summary, bioavailability of calcium from the calcium carbonate product was more dependent on estrogen treatment and vitamin D status than that of calcium citrate. This may explain the variable results of reported calcium supplementation studies.
authors.affiliation: Center for Mineral Metabolism and Clinical Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75390-8885, USA.
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Heller
authors.forename: John R
authors.initials: JR
authors.lastname: Poindexter
authors.forename: Beverley
authors.initials: B
authors.lastname: Adams-Huet
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001682:Biological Availability; D002118:Calcium / Q000097:blood; D002119:Calcium Carbonate / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019355:Calcium Citrate / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D004338:Drug Combinations; D004347:Drug Interactions; D004967:Estrogens / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D004338:Drug Combinations; D004967:Estrogens; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002119:Calcium Carbonate; D019355:Calcium Citrate; D002118:Calcium