Association between physical activity and vitamin D is partially mediated by adiposity in older adults: EpiFloripa Aging Cohort Study.

Studies have found that physical activity (PA) could be a protective factor and adiposity a risk factor for low serum 25-hydroxycholecalciferol (25(OH)D) concentration. This cross-sectional study hypothesized that PA could have a direct effect on 25(OH)D, and adiposity could be a mediating factor. Data from the second wave of the EpiFloripa Aging longitudinal study, collected during 2013 and 2014 (n = 1197) in Florianopolis, Santa Catarina, Brazil, was used. PA was measured using an accelerometer and classified as light PA (LPA), moderate and vigorous PA (MVPA), and total PA (TPA); 25(OH)D levels were measured using the microparticle chemiluminescence method. Body fat composition (%fat) was assessed using dual-energy X-ray absorptiometry. Structural equation modeling was performed to analyze the total, direct, and indirect effects of PA on %fat and 25(OH)D levels, presented using the standardized coefficient (β). Participants with complete data were included in the analysis (n = 574, 66.7% female). MVPA showed a direct (β = 0.11; P < .05) and total positive effect on 25(OH)D (β = 0.12; P < .05). All models of PA had a direct negative effect on %fat. Additionally, a direct negative effect of %fat on 25(OH)D was observed in all models. A marginal and partial effect of %fat as a mediator of the relationship between MVPA and 25(OH)D was noted (β = 0.01, P = .09). Our results show that PA presents a direct effect on serum 25(OH)D. %fat has a small contribution as a mediator of this relationship. These data suggest that an increase in MVPA and a decrease in %fat could be strategies to increase 25(OH)D levels in older adults.