effect of vitamin d supplement consumption on muscle strength, muscle function and body composition in vitamin d-deficient middle-aged women: a randomized clinical trial

background and objectives: sarcopenia is explained as the loss of muscle strength and muscle mass with aging‚ and is one of the major risk factors for metabolic diseases. cross-sectional studies demonstrate that vitamin d is associated with sarcopenia in both men and women. the aim of this study was to investigate the effect of vitamin d supplement consumption on muscle strength, muscle function and body composition in middle-aged women. materials and methods: in this randomized double-blind placebo-controlled trial, 71 women aged 40-55 years old, with the serum 25(oh)-d <25 ng/ml, were divided in two groups randomly, and received a 1000 iu vitamin d tablet (n=37) or a placebo (n=34), daily for 12 weeks. at the beginning and at the end of the study, dietary intake, anthropometric indices, muscle strength and function, serum 25(oh)-d, physical activity level and sun exposure were assessed. statistical analysis was performed with spss version 20. results: a significant difference in serum 25(oh)-d was found between the intervention and placebo groups at the end of the study (p<0.001). in the vitamin d group, handgrip strength was improved, while hand grip strength (p=0.233) and knee extension strength (p=0.337) between the two groups did not differ significantly after 12 weeks. the mean of timed get up and go test, decreased significantly in the vitamin d group compared to the controls (p<0.001). within the intervention group, body fat content decreased significantly after 12 weeks (p<0.001), but did not result a significant difference between the two groups (p=0.051). conclusions: it seems in this vitamin d-deficient middle-aged women group, 1000 iu vitamin d consumption daily for 12 weeks resulted in improvement of muscle function and body composition, but had no significant effect on muscle strength. keywords: vitamin d, muscle strength, muscle function, middle-aged women