New perspectives on vitamin D sources in Germany based on a novel mathematical bottom-up model of 25(OH)D serum concentrations

Up-to-date knowledge about vitamin D supply and serum concentration in Germany is not sufficient. Our purpose was to compare a novel holistic bottom-up modeling of 25(OH)D concentrations with vitamin D sources such as sunlight, food and supplements for all federal states taking seasonal and geographical variations into account. The second purpose was to update and detail vitamin D supply through food in Germany. To confirm the model of 25(OH)D concentrations, we used the population (1,763 men and 2,267 women, 18–79 years) participated in the representative German National Health Interview and Examination Survey 1998 and the integrated German Nutrition Survey. The maximum model value is 67.5 nmol/L in July and minimum model value is 29.3 nmol/L in January, while the average model value is 45.0 nmol/L. Men have a mean daily intake of 137 IU (3.42 μg) and women of 112 IU (2.79 μg). Correlation between model and actual data is 0.77 (p = 0.003). A comparison of the model data with population-based values showed good agreement. None of the vitamin D sources can provide the German population with enough vitamin D.