title: Serum 25-hydroxyvitamin D, ethnicity, and blood pressure in the Third National Health and Nutrition Examination Survey.
abstract: BACKGROUND
  Populations with low vitamin D status, such as blacks living in the US or UK, have increased blood pressure (BP) compared with whites. We analyzed the association between serum 25-hydroxyvitamin D (25OHD) and BP to determine whether low 25OHD explains any of the increased BP in blacks.
  
  
  METHODS
  The Third US National Health and Nutrition Examination Survey (NHANES III) is a cross-sectional survey representative of the US civilian population during 1988 to 1994. Analyses were restricted to 12,644 people aged > or =20 years with measurements of BP and 25OHD, after excluding those on hypertensive medication.
  
  
  RESULTS
  Adjusted mean serum 25OHD was lowest in non-Hispanic blacks (49 nmol/L), intermediate in Mexican Americans (68 nmol/L), and highest in non-Hispanic whites (79 nmol/L). When participants were divided into 25OHD quintiles, mean (standard error) systolic BP was 3.0 (0.7) mm Hg lower (P = .0004) and diastolic BP was 1.6 (0.6) mm Hg lower (P = .011) for participants in the highest quintile (25OHD > or =85.7 nmol/L) compared with the lowest (25OHD < or =40.4 nmol/L), adjusting for age, sex, ethnicity, and physical activity. Further adjustment for body mass index (BMI) weakened the inverse association between 25OHD and BP, which remained significant for systolic BP (P < .05). The inverse association between 25OHD and systolic BP was stronger in participants aged > or =50 years than younger (P = .021). Ethnic differences in 25OHD explained about half of the increased hypertension prevalence in non-Hispanic blacks compared with whites.
  
  
  CONCLUSIONS
  Vitamin D status, which is amenable to intervention by safely increasing sun exposure or vitamin D supplementation, was associated inversely with BP in a large sample representative of the US population.
authors.affiliation: School of Population Health, University of Auckland, Auckland, New Zealand. r.scragg@auckland.ac.nz
authors.forename: Robert
authors.initials: R
authors.lastname: Scragg
authors.forename: MaryFran
authors.initials: M
authors.lastname: Sowers
authors.forename: Colin
authors.initials: C
authors.lastname: Bell
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D003430:Cross-Sectional Studies; D003971:Diastole / Q000502:physiology; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D013599:Systole / Q000502:physiology; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D