The influence of elevated levels of sodium in drinking water on elementary and high school students in Massachusetts.

Continuing epidemiologic studies at the University of Massachusetts have examined the hypothesis that elevated levels of sodium (Na) in drinking water contribute to elevations of blood pressure (BP). Comparing tenth graders from a town with 107 mg Na/L in the drinking water to those from a town with 8 mg Na/L, revealed statistically significant and medically important higher BP distributions among the high Na town students relative to their low Na town peers for both systolic and diastolic BP in both boys and girls. The differences were upheld when potentially confounding factors, including dietary Na intake and other water factors occurring differentially in the two water supplies, were controlled in the analysis. A replication study among third graders in the same communities showed similar results. Most recently, an experimental bottled water study assessed the effect on blood pressure of lowering Na concentration in the water of some of the high sodium community fourth graders. For three months trios of children matched by sex, school, and baseline BP each used different water for all cooking and drinking purposes, with BP monitored bi-weekly. Pupils were randomly allocated to the three water conditions: 1) high sodium water bottled from their own community distribution system, 2) low sodium water bottled from the distribution system of the comparison community with sodium added to the level of the high sodium community water and 3) low sodium water bottled from the distribution system of the low sodium community but with no sodium added. Preliminary results indicate the BP levels of the girls on the low sodium water exhibited marked decreases in BP over the test period when compared to the other two groups.