Associations between objective and self-reported physical activity and vitamin D serum levels in the US population

Wanner, Miriam ; Richard, Aline ; Martin, Brian ; Linseisen, Jakob ; Rohrmann, Sabine

In: Cancer Causes & Control, 2015, vol. 26, no. 6, p. 881-891

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    Summary
    Purpose: Both low levels of vitamin D and of physical activity are associated with all-cause, cancer, and cardiovascular disease mortality. There is some evidence based on self-reported activity levels that physically more active individuals have higher vitamin D serum levels. The aim was to investigate associations between objectively measured and self-reported physical activity, respectively, and vitamin D serum concentrations in the US population. Methods: Data from NHANES 2003-2006 (n=6,370, aged ≥18years) were analyzed using multiple regression analyses. A total of 6,370 individuals aged 18years and older with valid data on vitamin D serum levels and physical activity were included. Objective physical activity was assessed using accelerometers; self-reported physical activity was based on the NHANES physical activity questionnaire. Results: An increase of 10min of objectively measured and self-reported moderate-to-vigorous activities per day was associated with an increase in circulating vitamin D of 0.32ng/ml (95% CI 0.17, 0.48) and of 0.18ng/ml (95% CI 0.12, 0.23), respectively. The odds ratio for being vitamin D deficient (<20ng/ml) if being insufficiently active compared with being sufficiently active was 1.32 (1.11, 1.57). Associations were not stronger for self-reported outdoor activities compared with indoor activities. Conclusions: Physical activity may be a way to achieve higher vitamin D serum levels in the population. Factors other than sun exposure that may be responsible for higher vitamin D levels in more active individuals need further investigation.