Effect of isolated vitamin D supplementation on bone turnover markers in younger postmenopausal women: a randomized, double-blind, placebo-controlled trial.

Vitamin D (VD) plays an important role in bone mineralization. The present study investigates the effect of VD supplementation alone on bone turnover markers in younger postmenopausal women. It has been shown that VD supplementation in postmenopausal women with hypovitaminosis D is associated with a reduction in bone turnover markers. PURPOSE: The purpose of this study is to evaluate the effect of VD supplementation alone on bone turnover markers in younger postmenopausal women. METHODS: In this double-blind, placebo-controlled trial, 160 women were randomized into the VD group (supplementation with 1000 IU of vitamin D3/day, orally; n = 80) or placebo group (n = 80). Women aged 50-65 years with amenorrhea ≥ 12 months and normal bone mineral density were included. The intervention lasted 9 months, and the participants were assessed at the beginning and end of treatment. Serum levels of total calcium, parathormone (PTH), alkaline phosphatase (AP), and 24-h urine calcium were determined. Serum C-terminal telopeptide of type I collagen (s-CTX) and procollagen type 1 N-terminal propeptide (P1NP) were measured by immunoassay as markers of bone resorption and formation, respectively. Plasma 25-hydroxyvitamin-D [25(OH)D] concentrations were measured by HPLC. Intention-to-treat analysis was performed using ANOVA, Student's t test, Tukey's test, and gamma distribution. RESULTS: Over the period of 9 months, 25(OH)D concentrations increased from 15.0 ± 7.5 to 27.5 ± 10.4 ng/mL (+ 45.4%) in the VD group and decreased from 16.9 ± 6.7 to 13.8 ± 6.0 ng/mL (- 18.5%) in the placebo group (p < 0.001). There was a decrease (- 21.3%) of PTH levels in the VD group with a significant difference between groups at the end of the study (p < 0.001). No significant differences were observed in the other laboratory parameters (total calcium, AP, and calciuria) in either group (p > 0.05). A comparison of bone turnover markers showed a significant reduction in of s-CTX (- 24.2%, p < .0001) and P1NP (- 13.4%, p = 0.003) levels in the VD group. No significant variations in bone turnover markers were observed in the placebo group (s-CTX, - 6.9%, p = 0.092 and P1NP, - 0.6%, p = 0.918). CONCLUSION: In younger postmenopausal women with VD deficiency, isolated supplementation with 1000 IU of vitamin D3 for 9 months is associated with a reduction in bone turnover markers. However, any between-group differences was not observed in bone turnover markers.

Effect of vitamin D supplementation alone on muscle function in postmenopausal women: a randomized, double-blind, placebo-controlled clinical trial.

UNLABELLED: The present study investigates the effects of vitamin D on muscle function in postmenopausal women. It has been shown that vitamin D supplementation in postmenopausal women with hypovitaminosis D provides significant protective factor against sarcopenia, with significant increases in muscle strength and control of progressive loss of lean mass. INTRODUCTION: We aimed to evaluate the effect of supplementation of vitamin D (VITD) alone on muscle function in younger postmenopausal women. METHODS: In this double-blind, placebo-controlled clinical trial, 160 Brazilian postmenopausal women were randomized into two groups: VITD group consisting of patients receiving vitamin D3 1000 IU/day orally (n = 80) or placebo group (n = 80). Women with amenorrhea for more than 12 months and age 50-65 years, with a history of falls (previous 12 months), were included. The intervention time was 9 months, with assessments at two points, start and end. Lean mass was estimated by total-body dual-energy X-ray absorptiometry (DXA) and muscle strength by handgrip strength and chair rising test. The plasma concentrations of 25-hydroxyvitamin D [25(OH)D] were measured by high-performance liquid chromatography (HPLC). Statistical analysis was by intention to treat (ITT), using ANOVA, Student's t test, and Tukey's test. RESULTS: After 9 months, average values of 25(OH)D increased from 15.0 ± 7.5 to 27.5 ± 10.4 ng/ml (+45.4%) in the VITD group and decreased from 16.9 ± 6.7 to 13.8 ± 6.0 ng/ml (-18.5%) in the placebo group (p < 0.001). In the VITD group, there was significant increase in muscle strength (+25.3%) of the lower limbs by chair rising test (p = 0.036). In women in the placebo group, there was considerable loss (-6.8%) in the lean mass (p = 0.030). CONCLUSION: The supplementation of vitamin D alone in postmenopausal women provided significant protective factor against the occurrence of sarcopenia, with significant increases in muscle strength and control of progressive loss of lean mass.