Increased fluid intake and blood pressure in healthy children: a randomized controlled trial. The SPA Project

High sodium intake is a key element in the development of hypertension, but strategies aimed at reducing its consumption have had limited impact at a population level. A potential alternative preventive and/or therapeutic opportunity may be represented by increasing kidney sodium excretion.

The Salus per Aquam Project is a multicenter, prospective, controlled, randomized study investigating whether, in healthy children, increased fluid intake for 1 year can lower blood pressure. Participants were randomized into 2 groups: one was actively encouraged to increase their water intake, especially during school days, while the other group was used as a control. At baseline and after 1 year, blood pressure was determined using multiple office blood pressure measurements. Urinary electrolytes and creatinine were measured in multiple samples at baseline, during the study period, and at the end of the study to provide details on sodium and fluid intake.

One hundred and seventy-five children were enrolled (94 females, 53.7%, median age 8.6 years, IQR:8.4-8.9), but only 145 completed the study. After 12 months, children who were motivated to drink more fluids presented lower median systolic (93 vs. 95 mmHg), diastolic (63 vs. 65 mmHg), and mean (73 vs. 74 mmHg) BP, compared with controls. The median change (ΔMBP, final-baseline) differed significantly between cases and controls, with a between-group median difference of 2 mmHg (Mann-Whitney p = 0.018).

An increased fluid intake may prevent the age-related increase of blood pressure in healthy children. We believe this may be due to more efficient sodium excretion by the kidneys. This simple, highly acceptable, inexpensive, and harmless intervention has the potential to prevent or lessen the prevalence of hypertension and associated illnesses both in adults and children.