Seasonal Changes in UVB Availability in Europe and Associations with Population Serum 25-Hydroxyvitamin D

The major source of vitamin D in humans is ultraviolet B (UVB) radiation in sunshine. It has been estimated that vitamin D production in skin provides between 80-100% of the body’s vitamin D requirements [2], and that food sources play a lesser role. Vitamin D is produced when UVB radiation reaches 7-dehydrocholestol in the skin, and there are a number of personal and environmental factors that can help or hinder this first step [3]. The personal factors include skin colour/pigmentation, age, clothing, use of suncreeen and sun exposure behaviour, while the environmental factors that determine if UVB radiation of sufficient strength is available for skin production of vitamin D include season, latitude and time of day.