Subjective evaluation of the frequency of salty food intake and its relationship to urinary sodium excretion and blood pressure in a middle-aged population

OBJECTIVES: The aim of this study was to examine the relationship between subjective evaluations of the frequency of salty food intake and both urinary sodium excretion and blood pressure (BP) in a middle-aged population. METHODS: Urinary sodium and creatinine concentrations in a spot sample and brachial BP were measured in 419 subjects (mean age 37±9 years, 385 men) during a health examination at a company in Kanagawa, Japan, 2011. Twenty-four-hour urinary sodium excretion was estimated from sodium and creatinine concentrations in the spot sample. The subjects were asked about the frequency of salty food intake on a self-reported questionnaire, choosing their answer from 'seldom', 'sometimes', or 'always' based on their own subjective evaluation. The amount of daily salt intake was converted from 24-h urinary sodium excretion. RESULTS: The prevalence of high salt intake, defined as greater than the daily average salt intake of Japanese according to the National Health and Nutrition Survey in 2010, gradually increased from the 'seldom' to the 'sometimes', and then 'always' categories (10.3, 13.4, and 24.0%, respectively; P=0.013 for trend). The 24-h urinary sodium excretion among these groups also tended to be different; however, the differences did not reach a significantly significant level (145±41, 152±34, and 160±40 mEq/day, respectively; P=0.076). Both systolic and diastolic BP were similar among the groups. CONCLUSIONS: Although some of our findings raise the possibility of a relationship between a subjective evaluation of the frequency of salty food intake and urinary sodium excretion, further studies are needed to confirm the relationship. In contrast, no relationship with BP was found.