Elevated salt and nitrate levels in drinking water cause an increase of blood pressure in schoolchildren

Aim: To assess the influence on blood pressure in schoolchildren, of elevated sodium (Na⁺) and nitrate NO₃/^- levels in the drinking water. Methods: The blood pressure was recorded in three groups of age- and weight-matched schoolchildren (fourth and fifth graders) ingesting differing Na⁺ and NO₃/^- concentrations with their drinking water. Group 1 (n = 452) imbibed high-Na⁺, high-NO₃/^- water (196 and 49 mg/l, respectively); group 2 (n = 418) consumed low-Na⁺, high-NO₃/^- water (25 and 49 mg/l, respectively) and group 3 (n = 86) drank low-Na⁺, low-NO₃/^- water (35 and 25 mg/l, respectively). The chloride (Cl^-) concentrations varied in parallel to those of Na⁺. Results: Systolic blood pressure (SBP) and mean arterial pressure (MAP) were significantly increased in group 1 versus groups 2 and 3 (115.6 ± 12.2 and 86.4 ± 9.6 mm Hg vs. 111.1 ± 11.6 and 83 ± 8.3 and 107 ± 8.8 and 81 ± 7.2 mm Hg, respectively, p < 0.05). The SBP in group 2 was also significantly higher than in group 3 (111.1 ± 11.6 vs. 107 ± 8.8 mm Hg; p < 0.05). Concluions: Elevated Na⁺ (and possibly Cl^-) in combination with high NO₃/^- concentrations in drinking water leads to an increase of SBP and MAP in fourth and fifth graders. The effects of Na⁺ (and/or Cl^-) and NO₃/^- on SBP and MAP appear to be additive, yet independent of each other. Copyright (C) 2000 S. Karger AG, Basel.