High adherence to a food guide may be associated with lower 24-hour urinary sodium excretion and sodium-to-potassium ratio, and higher potassium excretion.

Abstract

Background & aims: Salt reduction remains an important issue in population-level studies of diet. One unresolved issue is whether adherence to a food guide which does not assess dietary salt can lead to a reduction in salt intake.

Methods: This study aimed to investigate the association between adherence to a food guide calculated by weighed food records (WFRs) or a Food Frequency Questionnaire (FFQ), and urinary sodium and potassium excretion and sodium-to-potassium ratio. Further, salt-added scores were developed and analyzed. We used cross-sectional data, including data from 12-day WFRs, five 24-hour urine collections, and an FFQ. A total of 248 participants aged 35-80 years were surveyed between 2012 and 2013. Main outcomes were 24-hour urinary sodium and potassium excretion and sodium-to-potassium excretion ratio. Multiple regression analysis was performed with urinary excretion as the dependent variable and the food guide score calculated by WFRs and the FFQ as independent variables. Because scores are not proportional to intake under this food guide scoring method, Spearman's correlation coefficients were calculated between the score and urinary excretion, and between the number of servings and urinary excretion.

Results: When scored by WFRs, the higher food guide score group tended to have lower sodium excretion (-129 mg/day per one quartile increase; P for trend, 0.051), higher potassium excretion (137 mg/day per one quartile increase, P <0.01), and lower sodium-to-potassium ratio (-0.32 per one quartile increase, P <0.01). When accompanied by salt-added scores, total score was associated with further reductions in sodium excretion (-218 mg/day per one quartile increase; P for trend, <0.001).

Conclusions: Even with a study food guide which does not assess dietary salt, high adherence to the guide tended to be associated with lower sodium excretion and sodium-to-potassium ratio and higher potassium excretion. This inverse association with sodium excretion was strengthened by the addition of a salt-added score.