Effect of Ultraviolet Radiation on Blood Pressure, Cardiac Function and Insulin Sensitivity

The study hypothesis is that UVB, which increases body levels of vitamin D, when given to vitamin D deficient people in winter when the sun is weak, will lower blood pressure and insulin resistance, and improve cardiac function, compared with UVA which has no effect on vitamin D synthesis. All participants, both interviewers and myself will be blind to intervention. The UV is given by a nurse at a private dermatology clinic. She, the dermatologist at the clinic and the 3 members of an independent data monitoring committee, are the only people who know the allocation of the UV; plus a data entry person working for the data entry committee who keeps the baseline and follow-up bood results and who has no contact with participants.