A 4-Day Sodium-Controlled Diet Reduces Variability of Overnight Sodium Excretion in Free-Living Normotensive Adolescents

Abstract The present analysis examined changes in the variability of overnight sodium excretion in 84 free-living adolescents (ages 15 to 19 years) on a 4-day sodium-controlled diet in which foods provided were selected by adolescents from an extensive list of menu items. The only selection criterion imposed was that foods selected for each day contain 4,000±200 mg sodium. Adolescents collected overnight urine samples. Repeated measures analysis of variance tested the effect of diet day on overnight sodium excretion, overnight urinary sodium concentration, and overnight urinary volume. Variance ratio test evaluated changes in overnight sodium excretion variance across days. Day 4 overnight sodium excretion was statistically lower than days 1 to 3 (1.84 vs 6.54, 5.94, and 5.52 mEq/h [1.84 vs 6.54, 5.94, and 5.52 mmol/h]). Day 4 overnight urinary sodium concentration was lower than days 1 to 3 (32.16 vs 119.64, 109.61, and 111.32 mEq/L [32.16 vs 119.64, 109.61, and 111.32 mmol/L]). The variance of overnight sodium excretion from day 1 to day 4 was reduced 10-fold from 20.1 mEq/h (20.1 mmol/h) to 1.90 mEq/h (1.90 mmol/h). Daily overnight urine volumes remained constant, averaging 451.7 mL/day. The dietary protocol successfully reduced the variability of sodium intake as estimated by overnight sodium excretion in free-living adolescents. The protocol could be expanded to include baseline values, additional days of sodium control, and varying levels of dietary sodium intake.