Introduction: Obese persons may have low vitamin D levels due to behaviors (clothing, time outdoors) that can reduce synthesis of vitamin D. In overweight and obese individuals there are limited quantitative data regarding relationships among serum 25(OH)D, time spent outdoors, sun exposure, and clothing worn.
Methods: We assessed environmental and behavioral factors that contribute to cutaneous synthesis of serum 25(OH)D in 63 overweight and obese individuals enrolled in a 12-week controlled feeding clinical trial. Vitamin D content in the food was known and varied based on treatment group. Sun exposure was recorded bi-weekly from sun exposure logs that included date, time of day, location, activity, minutes in direct sun, clothing worn, and sunscreen use. UV-B radiation measured by UV-B Broadband Pyranometer and converted to J/m2. Total sun exposure (J) was measured as a product of UVB and total body surface area exposed from sun logs. Serum 25(OH)D was measured by RIA. Total body fat (TBF) and % body fat (%BF) was by DEXA. Intra-abdominal adipose tissue (IAAT) was by CT Scan.
Results: Sun exposure and % body surface area exposed (%BSAE) significantly correlated with serum 25(OH)D (r=0.2545, P=0.0441 and r=0.4614, P=0.0001, respectively). Time outside did not correlate with serum 25(OH)D (r=0.0387, P=0.763), but did relate to TBF (r=−0.3935, P=0.0014), %BF (r=−0.4132, P=0.0008), and BMI (r=−0.3987, P=0.0012). Sun exposure significantly correlated with only BMI (r=−0.2946, P=0.0191). %BSAE significantly correlated only with IAAT (r=−0.3526, P=0.0053).
Conclusion: We found a significant association between serum 25(OH)D and indices of cutaneous sun exposure, indicating that these variables should be considered when addressing the etiology of often-reduce vitamin D status in obese individuals.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details unavailable.
05 - 09 May 2012
European Society of Endocrinology