N05063: Dietary requirements for vitamin D: An investigation of the relative significance of dietary intake and sunlight on vitamin D status in young and elderly adults
Thursday 15 June 2006
This research project will determine the total vitamin D intake needed to prevent seasonal vitamin D deficiency.
Background
New evidence suggests that for a significant portion of the year most people are dependent on their diet to provide metabolically active vitamin D.
However, intakes of vitamin D are low and vitamin D status is inadequate in many people, particularly in late winter. The question of how much dietary vitamin D is required to maintain serum 25 (OH) D levels within an acceptable range all year round, particularly during winter, remains unanswered. In addition, the relative contribution of sunshine exposure and dietary intake to status needs to be established.
Research Approach
This study will follow a randomised controlled intervention design with 240 adults aged 20-40 and 65 years, across two centres (Cork and Northern Ireland). Subjects will be randomised to receive 0, 5, 10, 15micrograms/day of vitamin D3 throughout winter. Biomarkers of vitamin D status and habitual dietary intakes of vitamin D will be assessed at the beginning, middle and end of the intervention period. Sun exposure during the summer prior to intervention will also be assessed. The data will be used to determine the influence of vitamin D supplementation on vitamin D status during the winter months and thus will establish the amount of total dietary vitamin D needed to prevent deficiency during this time.