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

Objectives: To examine seasonality of 25-hydroxyvitamin D (25OH-D) levers i n 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 i n Britain during 1992-3 measured dietary intakes and blood status indices, including those for vitamin D, during all four seasons. The present study a ddresses the seasonal dependence of the relation between vitamin D intake a nd status. Setting: 100 randomly selected postcode sectors throughout Britain, whose l ocations were classified as (a) Scotland; (b) Northern England; (c) Central , Wales, South + SW; (d) London + SE. Subjects: Of 1859 whose parents or gu ardians were interviewed, 1675 provided a weighed diet estimate, and blood vitamin D status (25OH-D) was measured in 756, with approximately equal num bers in each season. Results: Vitamin D status is highly dependent on season: moreover, the rela tion between vitamin D intake and status is also seasonally dependent, bein g strong in the winter and negligible in the summer. During the winter, tho se children who had relatively low 25OH-D concentrations generally were tho se not receiving vitamin D supplements. Vitamin D intakes and supplement us e were lower in the north than in the south of Britain. Conclusions: For British preschool children, dietary vitamin D is of much g reater importance in the winter than in the summer. There is evidence of re gional inequality, with lesser use of supplements in the north. Supplements are needed in the winter, to achieve satisfactory vitamin D status and min imise 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 Agr iculture, Fisheries and Food and the Department of Health, and was conducte d by the Social Survey Division of the Office of Population Censuses and Su rveys (now the Office for National Statistics) and the MRC Dunn Nutritional Laboratory (now MRC Human Nutrition Research).