Suppression of parathyroid hormone and bone resorption by calcium carbonate and calcium citrate in postmenopausal women

The original publication can be found at www.springerlink.comThis study was conducted to compare the suppressive effects of calcium carbonate and calcium citrate on bone resorption in early postmenopause. Calcium citrate is thought to be better absorbed. We therefore tested the hypothesis that calcium as citrate is more effective than calcium as carbonate in suppressing parathyroid hormone (PTH) and C-terminal telopeptide. Twenty-five healthy postmenopausal women were recruited in this double blind crossover study. The subjects were randomly allocated to receive either 1,000 mg of elemental calcium as carbonate or 500 mg of calcium as citrate. They were given the alternate calcium dose 1 week later. Serum measurements of total and ionized calcium, phosphate, PTH, and CrossLaps were repeated 12 hours after each dose. Analysis of variance found no significant difference between measures for the two salts. Tests for equivalence indicated that 500 mg of calcium citrate may be superior to 1,000 mg of calcium carbonate in raising serum total and ionized calcium (P = 0.04 and 0.05, respectively). For all parameters measured, 500 mg of calcium citrate was at least as beneficial as 1,000 mg of calcium carbonate. Calcium citrate is at least as effective as calcium carbonate in suppressing PTH and C-terminal telopeptide cross-links, at half the dose. This may be because calcium as citrate is better absorbed than calcium as carbonate. If calcium citrate can be used in lower doses, it may be better tolerated than calcium carbonate.Sunethra D. C. Thomas, Allan G. Need, Graeme Tucker, Peter Slobodian, Peter D. O’Loughlin and B. E. Christopher Nordi

The effect of calcium supplementation on bone loss in 32 controlled trials in postmenopausal women

© International Osteoporosis Foundation and National Osteoporosis Foundation 2009SummaryIn 32 controlled trials of calcium supplementation (700-2000 mg) in 3,169 postmenopausal women, mean bone loss in the controls was -1.07% p.a. and in the treated subjects -0.27% p.a. (P for difference IntroductionWe have reviewed 32 trials of calcium supplementation in 3,169 postmenopausal women.MethodsWe found 24 publications reporting 32 controlled trials lasting at least 1 year, which provided annual percentage changes in bone mass or density at one or more sites in the calcium-treated and control subjects.ResultsThe median calcium supplement was 1,000 mg, median duration of the trials 2 years and total number of sites measured 79. The average of the mean rates of change in bone mass or density was -1.07% p.a. (P ConclusionCalcium supplementation of about 1,000 mg daily has a significant preventive effect on bone loss in postmenopausal women for at least 4 years.B. E. C. Nordi