03 Dec 2015 --- Certain genetic variations increase the risk of having a lower level of vitamin D. This is the finding of a PhD project from the National Food Institute, Technical University of Denmark, which has examined the effect of eating vitamin D fortified foods or receiving artificial UVB irradiation during the winter months. The fortified diet and artificial sunlight had less of an effect on vitamin D status in people with certain genetic variations. The results can be used to identify people who are genetically predisposed to having lower levels of vitamin D.