The most significant determinants of vitamin D status (serum 25(OH)D concentration, nmol/L).

1Mean serum 25(OH)D concentration (nmol/L) at end of Winter, the mean difference (95% confidence intervals; p-values) at the end of other seasons, and the effect of taking Vitamin D supplements, wearing protective clothing, and percentage body fat mass, were estimated using repeated-measures mixed methods linear regression analysis adjusted for age and time of subject visit. Variables for inclusion in this model were selected using stepwise regression from: Age, gender, sun exposure, sun avoidance, use of sunscreen, wearing hat, wearing protective clothing, weight, vitamin D supplements, dietary vitamin D, dietary fat as percentage of energy, saturated fat as percentage of total fat.
2Data was organised into four seasonal groupings, to enable investigation of the determinants of vitamin D status based on season rather than of specific time-points.
3The effect of wearing protective clothing and percentage body fat mass (as standardised normal transformations) on serum 25(OH)D concentration was expressed as the slope of the association: one standard deviation rise in each measure was associated with change shown in the table (95% confidence intervals of the slope; p-values).