Sodium and potassium intake measurements: dietary methodology problems.

This study compared methods that measured dietary intake of sodium and potassium by chemical analysis, by calculation from a table, and by measurement of these elements in 24-h urine. Total sodium included analyzed plus discretionary sodium. Analyzed elements were measured values in diets and urine performed by atomic absorption spectrophotometry. Calculated elements were estimated values from a food composition table. Food samples were collected by duplicate analysis. Total, analyzed, calculated, and discretionary sodium intake for 7 days by adolescent females averaged 2.890, 2.518, 1.852, and 0.372 g/day, respectively. Analyzed and calculated potassium intake by subjects averaged 1.447 and 1.667 g/day, respectively. Urinary sodium and potassium averaged 2.389 and 1.118 g/day, respectively. Subjects differed significantly in the amount of sodium ingested, partly due to discretionary sodium use. Total sodium and analyzed potassium were the accurate methods of determining sodium and potassium intake. Element intakes can be estimated from regression equations.