Normal man can maintain an over-all sodium balance at intakes varying from a few to 1000 mEq. or more of sodium daily. Although this balance is customarily referred to as a steady state, at all levels of sodium intake higher than a few milliequivalents daily it represents in reality a constantly fluctuating level of total body sodium. Each time sodium is ingested a positive balance is produced which is steadily reduced in the following hours by way of renal sodium excretion. This is well illustrated in a study from this laboratory1 in which identical meals and quantities of salt were administered to constantly recumbent subjects at six-hour intervals. Figure 1, plotted for the second day of this study, reveals that the sodium ingested at the beginning of each six-hour period has just about been eliminated by the end of the period, save for the night hours, particularly from midnight
STRAUSS MB, LAMDIN E, SMITH WP, BLEIFER DJ. Surfeit and Deficit of Sodium: A Kinetic Concept of Sodium Excretion. AMA Arch Intern Med. 1958;102(4):527–536. doi:10.1001/archinte.1958.00260210013003
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