Urinary sodium-to-potassium ratio: a simple and useful indicator of diet quality in population-based studies

Abstract

Background Current evidence regarding the prognostic relevance of urinary sodium-to-potassium ratio (Na-to-K ratio), as an indicator of diet quality is limited. This study was conducted to investigate whether urinary Na-to-K ratio could be related to habitual dietary patterns, in a general population. Methods This study was conducted in the framework of the Tehran Lipid and Glucose Study (2014–2017) on 1864 adult men and women. Urinary Na and K concentrations were measured in the morning spot urine samples. Dietary intakes of the participants were assessed using a validated 147-item Food Frequency Questionnaire (FFQ) and major dietary patterns were obtained using principal component analysis. Mediterranean dietary pattern and Dietary Approaches to Stop Hypertension (DASH) score, were also calculated. Multivariable-adjusted linear regression was used to indicate association of dietary patterns and urinary Na-to-K ratio. Results Mean (±\u2009SD) age of participants was 43.7\u2009±\u200913.9\xa0years and 47% were men. Mean (±\u2009SD) urinary Na, K and the ratio was 139\u2009±\u200941.0 and 57.9\u2009±\u200918.6\xa0mmol/L, 2.40\u2009±\u20090.07, respectively. Higher urinary Na-to-K ratio (>\u20092.37 vs.\u2009<\u20091.49) was related to lower intakes of vegetables (282 vs. 321\xa0g/day), low-fat dairy (228 vs. 260\xa0g/day) and fruits (440 vs. 370\xa0g/day). Western dietary pattern was related to higher urinary Na-to-K ratio ( β \u2009=\u20090.06; 95% CI 0.01, 0.16). Traditional dietary pattern, Mediterranean and DASH diet scores were inversely associated with urinary Na-to-K ratio ( β \u2009=\u2009−\u20090.14; 95% CI −\u20090.24, −\u20090.11, β \u2009=\u2009−\u20090.07; 95% CI −\u20090.09, −\u20090.01, β \u2009=\u2009−\u20090.12; 95% CI −\u20090.05, −\u20090.02, respectively). Conclusions Spot urinary Na-to-K ratio may be used as a simple and inexpensive method to monitor diet quality in population-based epidemiological studies.