Estimation of salt intake by a simple questionnaire

To assess whether a simple questionnaire could be used to categorize the subjects into different salt-intake groups, we compared the answers to four questions concerning food habits (total amount of food, number of bowls of miso soup, amount of pickles and saltiness of home-made pickles) with 24-hr urine NaCl levels of 1025 subjects from a Japanese farming village. The correlation coefficients between the scores from answers to the questions and urine NaCl by regression analysis were too low (< 0.3) to estimate salt intake correctly from the questionnaire. However, when the subjects were divided into four subgroups by the sum of the scores, the mean values of NaCl excretion increased with the total score (9.3 ± 4.9, 11.0 ± 4.1, 11.7 ± 3.8, 13.7 ± 5.6 g/day for males). Consequently this simple questionnaire is useful to classify the subjects roughly into different categories according to salt intake.