Interaction between diet and sunlight exposure on vitamin D status in premenopausal women living in Southern England: preliminary analysis of the Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England (D-FINES) Study

For Caucasian premenopausal women, using hierarchical multiple regression analysis, the two variables of most interest were added first (UV and vitamin D intake), with other physiologically-relevant variables that showed a significant correlation with vitamin D status being added next. For UV exposure in step 1 the model explained 6.1 % of variance in vitamin D status, a significant change (F change P 0.05). In steps 3 and 4 factor of sunscreen used and total body fat mass were entered into the model, and added 3.4% and 2 % of variance respectively (F change P > 0.05). Ca intake and age were not entered into the model, as they were not found to be significantly correlated with vitamin D status in this data subset, as has been found in other studies (2) . For the model as a whole the total variance in vitamin D status explained was 8.3% (adjusted R 2 0.083; F 4,73; P = 0.035). Standardised b coefficients were 0.191 for UV, 0.121 for dietary intake of vitamin D, - 0.167 for factor of sunscreen used and - 0.147 for total fat mass. However, none of these four variables made a significant unique contribution (P > 0.05) to vitamin D status. Overall, the regression model suggests that UVB, dietary intake, factor of sunscreen and total body fat mass make a small but significant contribution to determining vitamin D status, explaining approximately 8% of variance. Further analysis of the dataset is underway to determine the relative contribution of UVB exposure and dietary vitamin D intake to 25OHD status in Asian premenopausal women and the two post-menopausal Asian and Caucasian subgroups as well as determining, if possible, the specific unique contributions of each factor.