title: Dietary calcium, calcium supplementation, and blood pressure in African American adolescents.
abstract: BACKGROUND
  Intake of calcium from the diet is inversely associated with blood pressure in observational studies and animal models but randomized trials in humans have found only small effects of calcium supplementation on blood pressure. A blood pressure-lowering effect of calcium supplementation may thus be restricted to persons with a low intake of calcium from the diet and specific genetic or other characteristics.
  
  
  OBJECTIVE
  A randomized trial was conducted to assess the effect of calcium supplementation on blood pressure in African American adolescents. Rapid growth during adolescence may increase calcium requirements, and avoidance of milk and milk products by some African Americans can result in low intake of calcium.
  
  
  METHODS
  One hundred sixteen adolescents (65 girls, 51 boys; mean age: 15.8 y) were given calcium (1.5 g/d) or placebo for 8 wk in a randomized, double-blind, crossover design. Blood pressure was measured after 2, 4, and 8 wk. Dietary calcium was determined with a validated food-frequency questionnaire.
  
  
  RESULTS
  The net effect (+/-SE) of calcium supplementation on diastolic blood pressure was a reduction of 1.9 +/- 1.1 mm Hg (P = 0.04, one-tailed t test). Blood pressure reduction was greater in adolescents with lower intake of calcium from the diet (P = 0.003, one-tailed t test for interaction): -4.9 +/- 1.6, -2.3 +/- 1.6, and 1.4 +/- 1.8 mm Hg for change in the lower (0.024-0.067 g Ca/MJ), middle (0.069-0.091 g Ca/MJ), and upper (0.093-0.217 g Ca/MJ) tertiles, respectively. No main effect on systolic blood pressure was detected.
  
  
  CONCLUSIONS
  These findings suggest that calcium supplementation may lower diastolic blood pressure in African American adolescents with low dietary intakes of calcium.
authors.affiliation: Department of Preventive Medicine, Institute for Prevention Research, University of Southern California School of Medicine, Los Angeles 90033-4500, USA. jimdwye@hsc.usc.edu
authors.forename: J H
authors.initials: JH
authors.lastname: Dwyer
authors.forename: K M
authors.initials: KM
authors.lastname: Dwyer
authors.forename: R A
authors.initials: RA
authors.lastname: Scribner
authors.forename: P
authors.initials: P
authors.lastname: Sun
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: L M
authors.initials: LM
authors.lastname: Nicholson
authors.forename: I J
authors.initials: IJ
authors.lastname: Davis
authors.forename: A R
authors.initials: AR
authors.lastname: Hohn
mesh_terms: D000293:Adolescent; D001741:Black or African American / Q000706:statistics & numerical data; D044383:Black People; D001794:Blood Pressure / Q000187:drug effects*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male
chemical_list: D002136:Calcium, Dietary