Endocrine Abstracts

Objective: To systematically review and meta-analyze the best available evidence regarding the effect of vitamin D supplementation, either as monotherapy or in combination with protein and exercise, on sarcopenia indices (muscle strength, muscle mass, muscle performance).

Materials and methods: A comprehensive search was conducted in Medline, Cochrane Central, and Scopus databases, up to December 31^st, 2018. Data were expressed as standardized mean difference (SMD) with 95% confidence intervals (CI). I² index was employed for heterogeneity.

Results: An initial search identified 768 studies, 12 of which met the eligibility criteria for qualitative and quantitative analysis (n=1.470, age 78.4±7.6 years, follow-up 8–24 weeks). Vitamin D dosage was either 1,600 (n=2), 1,404 (n=1), 900 (n=1), 800 (n=3), 500 (n=2) or 100 IU/day (n=1), 10.000 IU thrice/week (n=1) or 300.000 IU, as a single dose (n=1). Concerning muscle strength, vitamin D supplementation was superior compared with placebo (n=9, SMD 0.41, 95% CI 0.133 to 0.689, P=0.004, I² 71). This was also evident when vitamin D was co-administered with protein (n=5, SMD 0.559, 95% CI 0.102 to 1.017, P=0.017, I² 84), whereas vitamin D monotherapy had no effect (n=4). Concerning muscle mass, vitamin D showed a marginal positive effect compared with placebo (n=4, SMD 0.23, 95% CI −0.003 to 0.472, P=0.053, I² 0). When vitamin D was co-administered with protein, a significantly positive effect was evident compared with placebo (n=2, SMD 0.371, 95% CI 0.002 to 0.740, P=0.049, I² 0). Concerning muscle performance, no effect was shown (n=2).

Conclusion: This is the first meta-analysis providing evidence that vitamin D supplementation increases muscle strength and mass in patients with sarcopenia, only when it is co-administrated with protein. Further well-designed studies are needed to clarify the effect of vitamin D supplementation on sarcopenia.