title: No effect of ultraviolet radiation on blood pressure and other cardiovascular risk factors.
abstract: OBJECTIVE
  Recent epidemiological studies have reported inverse associations between vitamin D status and blood pressure. The study aim is to determine if exposure to ultraviolet B radiation, which synthesizes vitamin D, lowers blood pressure, compared with ultraviolet A radiation.
  
  
  METHODS
  Men and women (n = 119) with low vitamin D levels [serum 25-hydroxyvitamin D [25(OH)D] <50 nmol/l], completed a randomized clinical trial carried out during winter. Blood pressure was measured for 12-14 h with an ambulatory monitor at baseline and 12 weeks. In between, participants received 24 whole body exposures of either ultraviolet B (n = 58) or ultraviolet A (n = 61) over 12 weeks.
  
  
  RESULTS
  Mean (SD) 25(OH)D increased from 43.7 (9.7) to 92.6 (16.9) nmol/l in the ultraviolet B arm after 12 weeks, and from 45.4 (9.2) to 64.9 (11.3) nmol/l in the ultraviolet A arm. However, mean blood pressure, which was similar for the ultraviolet B and ultraviolet A at baseline (134.9/79.2 vs. 132.9/77.8 mmHg; P = 0.59 and 0.56, respectively), did not change from baseline to 12 weeks in either group. The mean change [95% confidence interval (CI)] in blood pressure over this period in the ultraviolet B group compared with the ultraviolet A group was -2.2 (-7.8, 3.3) mmHg for systolic (P = 0.42) and -2.7 (-6.5, 1.0) mmHg for diastolic (P = 0.15).
  
  
  CONCLUSIONS
  Exposure to ultraviolet B did not lower blood pressure. Our results suggest that if vitamin D protects against cardiovascular disease, it involves some mechanism other than blood pressure.
authors: Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. r.scragg@auckland.ac.nz
authors: Robert
authors: R
authors: Scragg
authors: John
authors: J
authors: Wishart
authors: Alistair
authors: A
authors: Stewart
authors: Malakai
authors: M
authors: Ofanoa
authors: Ngaire
authors: N
authors: Kerse
authors: Lorna
authors: L
authors: Dyall
authors: Carlene M M
authors: CM
authors: Lawes
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000528:radiation effects*; D002319:Cardiovascular System / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014466:Ultraviolet Rays