Get access

Inaccuracy of self-reported low sodium diet

Authors

  • Linda M. Gerber,

    Corresponding author
    1. Department of Public Health, Weill Cornell Medical College, New York, New York 10065
    2. Division of Nephrology and Hypertension, Department of Medicine, Weill Cornell Medical College, New York, New York 10021
    • Department of Public Health, Weill Cornell Medical College, 402 East 67th Street, New York, NY 10065
    Search for more papers by this author
  • Samuel J. Mann

    1. Division of Nephrology and Hypertension, Department of Medicine, Weill Cornell Medical College, New York, New York 10021
    Search for more papers by this author

  • Disclosure: The authors have applied for intellectual property rights concerning related research directed toward development of a method for estimation of sodium excretion from spot urine samples. The necessary funding to perform this study was provided in part by Allied Minds, Inc., who has the right to license the patent.

Abstract

Objectives:

This study evaluates how often the self-report of a low sodium (Na) intake is reflected by a low 24-h urinary sodium excretion and examines the influence of incomplete urinary collections on this comparison.

Methods:

In a study in which 24-h urine collections were obtained for measurement of Na and creatinine excretion, 120 participants were asked whether their Na intake was low, medium, or high. A 24-h urine collection was considered complete if creatinine excretion was ≥20 mg/kg in men or ≥15 mg/kg in women, and incomplete if below those amounts. The kappa statistic was computed to assess the level of agreement between 24-h Na excretion, dichotomized at 100 meq and self-report responses.

Results:

Agreement between self-reported and actual Na excretion was poor. The kappa statistic was 0.18 for the total sample, 0.04 for complete collectors, and 0.51 for incomplete collectors, respectively. Overall, 24-h Na excretion exceeded 100 meq among 75% of those reporting an average or high Na intake, but it also exceeded 100 meq among 57% of those reporting a low sodium intake. Further, among those reporting a low sodium intake, Na excretion exceeded 100 meq in 80% of those who submitted a complete collection, but in only 29% of those who submitted an incomplete collection.

Conclusions:

These findings suggest that many individuals who report a low salt diet actually excrete ≥100 meq/day. Na intake is also frequently underestimated because many 24-h urine collections are incomplete. Am. J. Hum. Biol., 2012. © 2012 Wiley Periodicals, Inc.

Ancillary