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Published on: July 5, 2017
Vitamin d and physical activity status: associations with five-year changes in body composition and muscle function
David Scott1, Peter R Ebeling, Kerrie M Sanders
1NorthWest Academic Centre and Australian Institute for Musculoskeletal Science (D.S., P.R.E., K.M.S.), The University of Melbourne and Western Health, Sunshine Hospital, St Albans, Victoria 3021, Australia; School of Clinical Sciences (P.R.E.), Monash Medical Centre, Monash University, Clayton, Victoria 3168, Australia; and Menzies Research Institute (D.A., T.W., G.J.), University of Tasmania, Hobart, Tasmania 7000, Australia.
Context:
High vitamin D and physical activity (PA) levels are independently associated with improved body composition and muscle function in older adults.
Objective:
The objective of this study was to investigate the interaction of 25-hydroxyvitamin D (25OHD) and PA status in maintenance of body composition and muscle function in older adults.
Design And Setting:
This was a 5-year prospective population-based study of Australian community-dwelling older adults.
Participants:
Participants in the study included 615 community-dwelling volunteers aged 50 years old or older [61.4 ± 6.9 (mean ± SD) y; 48% female] randomly selected from electoral rolls and categorized according to baseline serum 25OHD (≥ or <50 nmol/L) and PA (≥ or <10,000 pedometer determined steps/d) levels as follows: high 25OHD and high PA (VitD+PA+); high 25OHD and low PA (VitD+PA-); low 25OHD and high PA (VitD-PA+); and low 25OHD and low PA (VitD-PA-). A subset of 518 participants completed accelerometer assessments during follow-up.
Main Outcome Measures:
Changes in dual-energy X-ray absorptiometry-assessed body composition and lower-limb muscle function were measured.
Results:
VitD+PA+ had significantly smaller increases in body fat over 5 years compared with other groups (all P < .05). Higher baseline pedometer-determined PA resulted in declines in total body fat (β = -.23 kg per 100 steps/d, P = .001) over 5 years for participants with high 25OHD but not those with low 25OHD (P > .05). Among participants with accelerometer data, these associations were generally mediated by higher levels of moderate/vigorous PA.
Conclusions:
High vitamin D status appears to enhance PA-related declines in body fat during aging, but the mechanism may be greater amounts of outdoor moderate/vigorous PA rather than a direct effect of 25OHD.
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