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Physical activity-related body fat decline linked to vitamin D status
In older adults, high vitamin D status may augment decreases in body fat related to physical activity and may also slow age-related declines in muscle quality, according to recent findings.
However, the mechanism of this association may be greater amounts of outdoor moderate/vigorous physical exercise, rather than a direct result of vitamin D, the researchers wrote.
In the 5-year, prospective, population-based study, researchers evaluated 615 community-dwelling adults enrolled in the Tasmanian Older Adult Cohort Study. Participants attended a clinic between March 2002 and September 2004 and were recruited to attend two follow-up clinics. One of these follow-ups (follow-up 1) took place 2 to 3 years after the baseline visit and the other (follow-up 2) occurred 5 to 6 years after baseline.
At baseline and one of the follow-up visits, researchers obtained the following information: self-reported employment and smoking status, comorbidity history, dietary energy and food intake, anthropometric measurements and muscle function, lower limb strength, physical activity and serum vitamin D concentrations. A subgroup of 518 participants were also evaluated for their exercise intensity during follow-up using an accelerometer.
According to their baseline and serum 25-hydroxyvitamin D (25-(OH)D; ≥ or <50 nmol/L) levels and physical activity assessments (≥ or <10,000 pedometer-determined steps per day), participants were divided into one of four groups: high 25-(OH)D and high physical activity (VitD+PA+), high 25-(OH)D and low physical activity (VitD+PA-), low 25-(OH)D and high physical activity (VitD-PA+) or low 25-(OH)D and low physical activity (VitD-PA-).
The study’s primary outcome measures were changes in DXA-evaluated body composition and lower limb muscle function. The researchers used multivariable linear regression to evaluate baseline differences, as well as differences in the change for each outcome variable from baseline to 5-year follow-up.
The researchers found that participants in the VitD+PA+ group had significantly smaller increased in body fat over 5 years vs. the other groups (all P<.05). Over 5 years, higher baseline pedometer-assessed physical activity yielded decreases in total body fat for those with high 25-(OH)D (P=.001), but higher baseline physical activity did not have this effect in those with low 25-(OH)D (P>.05).
In the subset of participants whose exercise intensity was measured by accelerometer, higher levels of moderate/vigorous physical activity were largely found to be mediators of these correlations.
According to the researchers, the role played by moderate/vigorous physical activity in this population may ultimately be a key finding of the study.
“Based on the findings of the present study, increased moderate/vigorous [physical activity] levels is likely to be a more effective therapy for improving body composition and physical function in generally health older adults than vitamin D supplementation,” the researchers wrote.
Disclosure: See the complete study for a full list of the researchers’ relevant financial disclosures.