Comparison of sodium and potassium intake with excretion.

Abstract

Nine well-motivated adults, knowledgeable about nutrition, kept food records, saved food portions equal to what was eaten and collected 24 h urine samples for 3 consecutive days. Estimates of Na and K intake were calculated from food table analyses of written food records and from flame photometric analyses of food portions. For each subject the mean of the estimates for each of the 3 days was compared with the mean of urine analyses for Na and K for each of the 3 days. For the group of 9 subjects, the average estimate of Na intake from analyses of food records was 11% lower than the average estimate of urinary Na excretion; the average estimate of Na intake from analysis of food portions was 2% higher than urinary Na excretion. For individuals, there were large differences between estimates of intake and measurement of Na excretion. For the group of 9 subjects, the average estimate of K intake from analysis of food records was < 1% lower than the average estimate of K urinary excretion; the average estimate of K intake from analysis of food portions was 13% higher than K urinary excretion. For individuals, as with Na, there were large differences between estimates of intake and measurement of K excretion.