Development and validation of a short questionnaire to assess sodium intake

Public Health Nutr. 2008 Jan;11(1):83-94. doi: 10.1017/S1368980007000146. Epub 2007 Jun 21.

Abstract

Objectives: To develop and validate a short food-frequency questionnaire to assess habitual dietary salt intake in South Africans and to allow classification of individuals according to intakes above or below the maximum recommended intake of 6 g salt day-1.

Design: Cross-sectional validation study in 324 conveniently sampled men and women.

Methods: Repeated 24-hour urinary Na values and 24-hour dietary recalls were obtained on three occasions. Food items consumed by >5% of the sample and which contributed > or =50 mg Na serving-1 were included in the questionnaire in 42 categories. A scoring system was devised, based on Na content of one index food per category and frequency of consumption.

Results: Positive correlations were found between Na content of 35 of the 42 food categories in the questionnaire and total Na intake, calculated from 24-hour recall data. Total Na content of the questionnaire was associated with Na estimations from 24-hour recall data (r = 0.750; P < 0.0001; n = 328) and urinary Na (r = 0.152; P = 0.0105; n = 284). Urinary Na was higher for subjects in tertile 3 than tertile 1 of questionnaire Na content (P < 0.05). Questionnaire Na content of <2400 and > or =2400 mg day-1 equated to a reference cut-off score of 48 and corresponded to mean (standard deviation) urinary Na values of 145 (68) and 176 (99) mmol day-1, respectively (P < 0.05). Sensitivity and specificity against urinary Na > or =100 and <100 mmol day-1 was 12.4% and 93.9%, respectively.

Conclusion: A 42-item food-frequency questionnaire has been shown to have content-, construct- and criterion-related validity, as well as internal consistency, with regard to categorising individuals according to their habitual salt intake; however, the devised scoring system needs to show improved sensitivity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adult
  • African Continental Ancestry Group
  • Aged
  • Blood Pressure
  • Case-Control Studies
  • Cross-Sectional Studies
  • Diet Records*
  • Female
  • Humans
  • Hypertension
  • Male
  • Middle Aged
  • Nutrition Assessment*
  • Sensitivity and Specificity
  • Sodium, Dietary / administration & dosage*
  • Sodium, Dietary / analysis
  • Sodium, Dietary / classification*
  • Sodium, Dietary / urine
  • South Africa
  • Surveys and Questionnaires / standards*

Substances

  • Sodium, Dietary