Estimation of dietary sodium intake in children.

To examine the utility of nocturnal urine collections in the estimation of dietary sodium intake in children, 29 families who agreed to lower their dietary sodium intake to less than 65 mEq/d were studied. A total of 58 adults and 95 children collected urine specimens weekly or biweekly before and after being instructed in a dietary sodium restriction regimen. Urine collections were fractionated into a diurnal and nocturnal portion. Sodium was measured directly, and estimated by measuring chloride excretion with a chloride titrator stick. Nocturnal chloride and 24-hour sodium excretion were highly correlated in adults (r = .75), and slightly less so (r = .56) in children. The slopes of the relationships were not different. Discriminant analysis showed that two or more chloride estimates permitted classification of both adults and children into the low sodium intake category with 100% accuracy, and into the normal sodium intake category with 75% accuracy. It was concluded that nocturnal chloride estimates are as useful in estimating compliance to a reduced sodium intake in children as in adults.