Discussion
overweight, disability
OBESE, VITAMIN D DEFICIENCY
This 24-week RCT demonstrated that 4000 IU/day vitamin D supplementation had no effect on gait speed when taken with or without exercise. Following multi-modal exercise, vitamin D supplementation decreased waist circumference compared with placebo in overweight or obese older adults with vitamin D deficiency. This finding may be clinically relevant as vitamin D supplementation is a safe, low-cost addition to formal exercise programs, especially in vitamin D-deficient individuals. Vitamin D supplementation taken alone also reduced stair climb times; however, it had no beneficial effects on other biochemical, body composition or physical function parameters when taken alone or during exercise.Increases in serum 25(OH)D levels following high-dose vitamin D supplementation have been well-documented in overweight or obese populations with vitamin D deficiency [Following multi-modal exercise, vitamin D supplementation decreased waist circumference compared with placebo, which also led to greater WHR decreases. This finding was also observed in most of our subgroup analyses. Improvements in WHR following high-dose vitamin DVitamin D supplementation taken alone and in combination with exercise had no beneficial effects on muscle density. Our sub-analysis in men showed that vitamin D supplementation increased muscle density during exercise, however, this finding should be interpreted with caution given the low numbers in our subgroups. Muscle density is an indirect measure of inter- and intramuscular adipose tissue (IMAT), and lower muscle density is associated with poor mobility [Stair climb times improved in response to vitamin D supplementation alone, but not in combination with exercise. We previously reported higher 25(OH)D levels are associated with better stair climb times in overweight or obese older women, but not men [The LIFE study we based our exercise intervention on reported reduced risk for disability in an at-risk population of older adults (aged 70–89 years) with physical function limitations (inclusion criteria: SPPB scores ≤ 9 or inability to walk 400 m) following multi-modal exercise [Consistent with our findings, recent meta-analyses have showed that vitamin D supplementation alone had no beneficial effect on muscle strength, size and performance [Strengths of this study included a well-characterized overweight/obese population with low baseline serum 25(OH)D levels, a comprehensive battery of physical function tests, data on important potential confounders, as well as the successful delivery of an evidence-based, multi-modal exercise program designed to be undertaken in a home-based setting to increase translatability and implementation [In conclusion, vitamin D