Vitamin D: seasonal and regional differences in preschool children in Great Britain

Objectives: To examine seasonality of 25-hydroxyvitamin D (25OH-D) levers in British preschool children and the effect of vitamin D supplementation on this. Design: The National Diet and Nutrition Survey of children aged 1.5-4.5 y in Britain during 1992-3 measured dietary intakes and blood status indices, including those for vitamin D, during all four seasons. The present study addresses the seasonal dependence of the relation between vitamin D intake and status. Setting: 100 randomly selected postcode sectors throughout Britain, whose locations were classified as (a) Scotland; (b) Northern England; (c) Central, Wales, South + SW; (d) London + SE. Subjects: Of 1859 whose parents or guardians were interviewed, 1675 provided a weighed diet estimate, and blood vitamin D status (25OH-D) was measured in 756, with approximately equal numbers in each season. Results: Vitamin D status is highly dependent on season: moreover, the relation between vitamin D intake and status is also seasonally dependent, being strong in the winter and negligible in the summer. During the winter, those children who had relatively low 25OH-D concentrations generally were those not receiving vitamin D supplements. Vitamin D intakes and supplement use were lower in the north than in the south of Britain. Conclusions: For British preschool children, dietary vitamin D is of much greater importance in the winter than in the summer. There is evidence of regional inequality, with lesser use of supplements in the north. Supplements are needed in the winter, to achieve satisfactory vitamin D status and minimise the risk of rickets and of poor bone health, especially in high-risk groups. Sponsorship: This study was part of the National Diet and Nutrition Survey of Children Aged 1.5-4.5 y, which was funded jointly by the Ministry of Agriculture, Fisheries and Food and the Department of Health, and was conducted by the Social Survey Division of the Office of Population Censuses and Surveys (now the Office for National Statistics) and the MRC Dunn Nutritional Laboratory (now MRC Human Nutrition Research).