Effects of Dietary-Derived Vitamin D and Sunlight-Derived Vitamin D on Immune Function

Supervisors: Prof H Macdonald, Dr A Ormerod and Dr M Vickers

There is concern about vitamin D deficiency at high latitude but we are unclear about how much we need for optimum immune function. There appears to be some resistance to increasing 25-hydroxyvitamin D [25(OH)D] (a marker of vitamin D status) with higher doses of oral vitamin D [1]. Cutaneous synthesis of vitamin D is only possible in the UK between April and September, when sufficient intensity of UV light of the appropriate wavelength is available [2-4]. Our pilot study showed that narrow band UVB treatment of dermatology outpatients during winter in Aberdeen increased regulatory T-cells alongside increasing 25(OH)D [5]. Interleukin 10, was noted to change in parallel with the UV dose, but not in line with 25(OH)D. We wish to test whether an oral dose of vitamin D in the winter improves markers of immune function in healthy individuals and whether this is the same as exposure to natural sunlight during summer in the UK. We will also test whether giving oral vitamin D in the summer gives further benefit over sunlight or whether it could interfere with modulation of immunity through UV effects on the skin, by suppressing cutaneous vitamin D synthesis.