Changes in bone turnover markers after calcium-enriched milk supplementation in healthy postmenopausal women: a randomized, double-blind, prospective clinical trial

Abstract

To assess the effect of calcium, phosphorus, lactose, and vitamin D fortified skimmed milk on biomarkers of bone turnover in healthy postmenopausal women. The design was of a prospective, double-blind, randomized, 6 months study. Eighty postmenopausal women (aged 49-71 y) were allocated in two groups receiving 750 mL/day of a fortified skimmed milk containing 1,200 mg of calcium and 5.7 microg of vitamin D (group A) or 900 mg of calcium and 5.7 microg of vitamin D (group B). Ultrasound bone mass measurements and biochemical markers of bone formation, serum bone-specific alkaline phosphatase (AP), and carboxi-terminal propeptide of type I procollagen (PICP) and of bone resorption, urinary excretion of pyridinoline (Pyr), deoxypyridinoline (D-Pyr), and urinary type I collagen cross-linked N-telopeptide (NTx) were performed at baseline and after 10 weeks and 6 months of follow-up. PICP levels showed a significant reduction during the study, but no differences were observed between groups (-18.47 +/- 11.4 group A vs -14.42 +/- 12.5 group B). Pyr levels decreased in group A (P < 0.001), whereas no changes were detected in group B. At the end of the study, a significant difference (P < 0.01) was detected between groups in Pyr (-23.66 +/- 5.7 group Avs 3.465 +/- 7.1 group B) and D-Pyr (-16.64 +/- 1.6 group Avs 2.955 +/- 2.1 group B). At the 6th month, serum 25OH vitamin D increased in group A and decreased in group B (P = 0.007). Additionally, no differences were observed between groups in bone mass and in the other bone markers. Body weight was unchanged for group A, whereas a significant increase was observed in group B. The daily intake of 750 mL of enriched skimmed milk containing 1,200 mg of calcium appears to be a useful, safe, and acceptable measure to calcium supplementation in healthy elderly postmenopausal women.