Fluid intake and blood pressure in children: the Salus per Aquam project.

Background: Sodium intake is known to contribute to the development of hypertension, thus intake reduction is a cornerstone in the prevention and management of hypertension. The increase in renal sodium excretion might represent a further potential preventive and/or therapeutic opportunity.

Objective: To explore the working hypothesis that an increased fluid intake can improve renal sodium handling towards a decrease in blood pressure.

Methods: The SPA Project is a multicenter, observational, cross-sectional, cohort study investigating healthy children, aged 5-8 years as to sodium and fluid intake by means of urinary sodium and creatinine from multiple samples taken in different days in order to characterize them in lower/higher sodium and lower/higher fluid intake. Both SBP and DBP (by multiple office blood pressure measurements) were used as outcome measures.

Results: Three hundred and thirty-nine healthy, nonoverweight children (51.6% boys) with a median age of 5.7 years old (IQR: 5.3-6.2) participated in the study but only 223 could be analyzed. Among children with higher sodium intake, those introducing more fluids, showed a significantly lower blood pressure (both systolic and diastolic) compared with those with lower fluid intake: systolic 86.0 ± 8.5 vs. 90.0 ± 8.1 mmHg; P = 0.014 and diastolic: 53.8 ± 4.9 vs. 58.6 ± 6.6 mmHg; P < 0.0001.

Conclusion: An increased fluid intake is associated with a reduced blood pressure possibly by increasing renal sodium excretion. We speculate that this simple, highly acceptable, inexpensive, and harmless measure might have a role in preventing and/or minimizing the epidemics of hypertension and of its related morbidities both in children and in adults.