The main source of vitamin D in humans is the conversion of
7-dehydrocholesterol (7-DHC) in the epidermis to previtamin D 3,
which isomerizes to form vitamin D 3 . Seasonal and local varia-tions of ultraviolet (UV) radiation, increasing indoor activities,
but also public awareness of the hazardous effects of sun expo-sure that lead to sun avoidance strategies or the use of sun-screens limit the endogenous synthesis of vitamin D 3.Asa
consequence, the need for vitamin D from food sources is on
the rise