Assessment of sodium intake by a short dietary questionnaire

The aim of the study was to develop a short questionnaire for classifying persons according to their use of salt in public health work. After pretesting the questionnaire it was modified to measure the saltiness of diet. It consisted of five questions concerning certain salting habits and self-rating of salt use, and the frequency of use of seven salty food items. The questionnaire was completed by 1471 persons aged 14 to 65 who also collected one 24-hour urine sample. A sum index of all the questions was formed and called the Salt Index (SI). The correlation between the 24-hour urinary sodium excretion and SI was 0.18 in men and 0.20 in women (both significant at p less than 0.001). Men and women were classified into three groups according to their SI: low representing the lowest quintile, high representing the highest and medium containing all the other quintiles. The mean 24-hour urinary sodium excretion was lowest in the low SI-category and highest in the high SI-category in both men and women. The subjects were further divided into light and heavy workers on the basis of their occupation. In this analysis the effect of both energy intake and the saltiness of the diet indicated by SI were clearly distinguished. Women doing light work and having a low SI had the lowest sodium excretion value, 148 mmol/day, and men doing heavy work and having a high SI had the highest, 260 mmol/day.