Development of a method for estimating dietary salt intake using the overnight urinary sodium/potassium ratio_20210802

There are many patients who need to restrict and assess salt in their diet. However, it is difficult to estimate daily salt intake accurately and easily. Therefore, a method for estimating dietary salt intake using the overnight urinary sodium (Na)/potassium (K) ratio was developed. The study involved 43 healthy adults (13 males, 30 females). From 2018 to 2020, subjects consumed a salt-adjusted diet for 11 to 30 days continuously, and overnight urine was collected daily. Using the previous day’s salt intake as the objective variable, an equation for estimating the salt intake was developed using a general linear model. To verify the accuracy of the estimating equation, the estimated salt intake of the previous day was calculated using our equation and Tanaka’s equation, respectively, and they were compared with the actual salt intake. The results of the analysis showed that Model1 was the optimal model. The Pearson’s product-moment correlation coefficient between the actual and estimated salt intake was r = 0.618 (P < 0.001) and r = 0.573 (P < 0.001) for the Model 1 estimates and Tanaka’s equation estimates, respectively. The percentages of errors within ±30% from the actual salt intake were 64.2% and 58.4% for Model 1 and Tanaka’s equation, respectively. The percentages of errors within ±1.0 g from the actual salt intake were 25.0% and 25.6% for Model 1 and Tanaka’s equation, respectively. The estimating equation developed is simple and may be a useful method for daily monitoring of dietary salt intake.