Abstract
Abstract
Introduction: The effect of vitamin D supplementation on physical performance is controversial. Longitudinal cohort studies show very low levels of serum 25OHD (< 15- 20ng/ml) are associated with lower physical performance. There are few clinical trials of the effect of vitamin D on physical performance and results are mixed. Design: 163 white and 110 black independent living women entered a 12-month double blind randomized dose ranging study of daily vitamin D,400,800,1600,2400,3200,4,000,4800IU or placebo together with calcium supplement as needed for a total intake of 1200mg and mean diet vitamin D of 114 IU. Inclusion criteria: total serum 25OHD ≤ 20ng/ml (Diasorin RIA); no known disease or drugs affecting calcium or bone metabolism. Physical performance tests were performed at baseline and end as described in the Short physical performance battery (SPPB) that included Balance, Timed walk, Chair rising test. Additional tests included Timed up and Go, Grip strength and Balance (Biodex). Fall history was recorded at baseline and at 3-monthly visits. Serum 25OHD was measured by Diasorin RIA and LCMS, Free 25OHD was measured by Elisa (Future Diagnostics). Changes in physical performance and fallers were analyzed by dose groups and by quintiles of total and free serum 25OHD. This was a secondary analysis using Intent to treat strategy. Chi square and ANOVA determined association between dose, quintiles and tests. Results: Mean age 66.2 years (SD 7.3, range 57–87), mean BMI 30.3 kg/m2 (SD 5.9). Compliance, measured every 3 months, was 94% for vitamin D and 91% calcium. 147 White and 89 Black women completed study. There was significant better performance in physical performance in women < age 70 years compared to > age 70 years. Black women performed better with all tests except grip strength after adjustment for age and BMI. When the absolute change in test performance was examined according to serum total or free 25OHD quintiles there was no correlation between serum levels of 25OHD and change in any physical performance test except for an improvement in chair rising test in younger Black women. Conclusions: There is no significant effect of vitamin D on physical performance in either black or white women. In a previous analysis we found a significant U-shaped response in fall incidence in the serum 25OHD range 30-40ng/ml but in this analysis there is no correlation between physical performance of fallers versus non- fallers