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

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