Quantifying the non-food sources of basal vitamin D input

Unsupplemented vitamin D status is determined by cutaneous synthesis and food inputs; however, their relative magnitudes are largely unknown. In a cohort of 780 non-supplement-taking adults with a mean serum 25-hydroxyvitamin D [25(OH)D] of 33 (±14) ng/ml we assessed the relationship between serum 25(OH)D and non-food environmental variables. Serum 25(OH)D concentration was adjusted for seasonal influence (which removed 2% of the total variance) and these adjusted values were regressed against factors involved in cutaneous synthesis. Indoor tanning use, sun exposure, and percent of work performed outdoors were significantly positively associated and body mass index (BMI) was significantly negatively associated with 25(OH)D values (P <0.03 for each). Latitude, gender, and age were not significantly correlated (P > 0.10). Season and non-food predictors together explained 13% of the total variance in serum 25(OH)D concentration. Non-traditional food sources need to be investigated as possible vitamin D inputs. This article is part of a Special Issue entitled 'Vitamin D Workshop'.