Effect of calcium phosphate and vitamin D3 supplementation on bone remodelling and metabolism of calcium, phosphorus, magnesium and iron

Background: The aim of the present study was to determine the effect of calcium phosphate and/or vitamin D-3 on bone and mineral metabolism. Methods: Sixty omnivorous healthy subjects participated in the double-blind, placebo-controlled parallel designed study. Supplements were tricalcium phosphate (CaP) and cholecalciferol (vitamin D-3). At the beginning of the study (baseline), all subjects documented their normal nutritional habits in a dietary record for three successive days. After baseline, subjects were allocated to three intervention groups: CaP (additional 1 g calcium/d), vitamin D-3 (additional 10 mu g/d) and CaP + vitamin D-3. In the first two weeks, all groups consumed placebo bread, and afterwards, for eight weeks, the test bread according to the intervention group. In the last week of each study period (baseline, placebo, after four and eight weeks of intervention), a faecal (three days) and a urine (24 h) collection and a fasting blood sampling took place. Calcium, phosphorus, magnesium and iron were determined in faeces, urine and blood. Bone formation and resorption markers were analysed in blood and urine. Results: After four and eight weeks, CaP and CaP + vitamin D-3 supplementations increased faecal excretion of calcium and phosphorus significantly compared to placebo. Due to the vitamin D-3 supplementations (vitamin D-3, CaP + vitamin D-3), the plasma 25-(OH)D concentration significantly increased after eight weeks compared to placebo. The additional application of CaP led to a significant increase of the 25-(OH)D concentration already after four weeks. Bone resorption and bone formation markers were not influenced by any intervention. Conclusions: Supplementation with daily 10 mu g vitamin D-3 significantly increases plasma 25-(OH)D concentration. The combination with daily 1 g calcium (as CaP) has a further increasing effect on the 25-(OH)D concentration. Both CaP alone and in combination with vitamin D-3 have no beneficial effect on bone remodelling markers and on the metabolism of calcium, phosphorus, magnesium and iron.