The vitamin D content of conventional food is very low. Therefore, more than 50% of German adults suffer from vitamin D deficiency, but even so, a general fortification of food is highly regulated in order to prevent consumers from vitamin D intoxication. The present thesis manly focuses on the examination of alternative strategies to increase vitamin D content of animal products. An efficient increase was observed particularly in chicken eggs in response to an ultraviolet (UV) light exposure of the laying hens. Within these studies, both daylight and artificial UV light regimes were associated with a 4- to 8-fold increase of vitamin D content. An exposure of unfeathered leg skin was most effective due to the very high 7-dehydrocholesterol content. Even long UV exposure times were not linked to critically high vitamin D contents in egg yolk. Thus, the examined strategy offers a safe approach with respect to consumer safety.