The measurement of sodium and potassium intake.

Single- vs multiple-day food records were compared for estimates of intake for sodium, potassium, and calories; and the correspondence was assessed between sodium and potassium intake and 24-h urinary excretion. Fifty-five middle-aged adults, participating in a prerandomization assessment for a nutritional/behavioral intervention program on blood pressure completed a six-day food record and a 24-h urine collection. The group average for sodium, potassium, and calories obtained from one-day food records proved to be as good an estimate of the six-day average as did values from multiple day records. Similarly the one-day food record proved a good estimate of the mean 24-h urinary values for sodium and potassium. If properly collected and analyzed, a one-day food record is a good estimate of a population's intake of sodium and potassium while multiple days of recording are necessary to characterize individual intake.