Vitamin D and Immunity: Photosynthesis Versus Supplementation (IMMUNI-D)

The optimal way to restore serum 25-hydroxyvitamin D sufficiency is currently debatable. UV irradiation through sunshine exposure promotes endogenous vitamin D synthesis, although this can also be associated with a risk of UVR-induced skin cancer. Dietary supplements represent an alternative, which are increasingly being used in clinical trials to correct deficiency. However, it is unclear whether sunshine exposure and vitamin D supplementation induce comparable changes in immune function, or whether additional UVR-induced molecules may be responsible for proposed health benefits. Several studies report an inverse correlation between exposure to UVR and immune-mediated diseases, further supporting the theory that UVR may also be protective through non vitamin-D mediated pathways. So far it has been difficult to distinguish between immune-regulation by vitamin D and other mediators induced by UVR as the downstream effects are similar. A direct comparison of the biological effects of vitamin D obtained by UVR versus supplementation has never been made. This study aims to elucidate the differences in vitamin D generated by UVR exposure versus supplementation by comparing immunological endpoints

Vitamin D status of healthy participants treated with oral vitamin D (cholecalciferol) or UVR (SSR) exposures and control (untreated)

Frequency of major peripheral immune cells (e.g. CD3+ T cells, CD3+ CD4+ T cells, CD3+ CD8+ T cells, CD19+ B cells, Natural Killer Cells, Classical, Non-classical and Intermediate Monocytes) in participants when vitamin D insufficient and sufficient. Via flow cytometry.

Frequency of peripheral blood dendritic cells (myeloid and plasmacytoid) in individuals with insufficient vitamin D levels and following vitamin D repletion via supplementation or UVR (SSR) exposures. Assessment of markers of maturation/tolerogenicity (MFI and frequency expressing) on myeloid and plasmacytoid dendritic cells direct ex vivo and after stimulation in vitro in participants when vitamin D insufficient and sufficient.

Differentially regulated genes in myeloid and plasmacytoid dendritic cells in participants after vitamin D repletion via supplementation and UVR (SSR) exposure via Microarray.

Inclusion Criteria: Age: 18-40 Fitzpatrick skin type I/II Healthy Serum 25(OH)D3 <50nmol/L Exclusion Criteria: Serum 25(OH)D3 >50nmol/L Pregnant or nursing women Women of child bearing age not using adequate contraception Are taking photosensitizing medication (i.e. causes you to be more sensitive to sunlight) Have had a history of skin disorders, sensitive skin, sensitivity to sunlight or skin cancer Have previously had an organ transplant Have partaken in a clinical study within the last 14 days Have had recent exposure to sunbeds (last 4 months) or holiday sun (including skiing) Are currently or have taken vitamin D supplements in the last 4 months Are asthmatic or suffer from any allergies