Up to a third of children aged 4 to 10 years and approximately 40% of adolescents have low vitamin D levels. As a result, rickets and other skeletal problems linked to vitamin D deficiency seem to be re-emerging. Meanwhile, biologists increasingly recognise that vitamin D has numerous roles beyond bone metabolism and calcium homoeostasis. Indeed, low levels may predispose to several chronic conditions, including osteoporosis, diabetes, some cancers, as well as certain cardiovascular, inflammatory and autoimmune diseases, such as multiple sclerosis. Against this background, NICE suggests that people working in nurseries, schools and children's centres should ‘raise awareness of the importance of vitamin D supplements among the local population’.