Vitamin D from Viridian Nutrition Vitamin D is an essential nutrient that contributes to the normal function of the immune system and blood calcium levels which in turn supports the maintenance of normal bones and teeth. As fear of sun-exposure has grown and lifestyles have become more sedentary, exposure to the sun has dropped dramatically and vitamin D deficiency and the incidence of rickets has surged. The skin cannot create vitamin D if covered in sunscreen or clothing, it is thought that a sun cream with SPF15 will reduce the skin’s ability to synthesize vitamin D by more than 95%. Many older people and those from the communities who tend to wear more modest clothing are amongst the population groups most likely to suffer deficiency in vitamin D.