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 (NO(-)(3)) 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 NO(-)(3) concentrations with their drinking water. Group 1 (n = 452) imbibed high-Na(+), high-NO(-)(3) water (196 and 49 mg/l, respectively); group 2 (n = 418) consumed low-Na(+), high-NO(-)(3) water (25 and 49 mg/l, respectively) and group 3 (n = 86) drank low-Na(+), low-NO(-)(3) 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).

Conclusions: Elevated Na(+) (and possibly Cl(-)) in combination with high NO(-)(3) 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 NO(-)(3) on SBP and MAP appear to be additive, yet independent of each other.