Accuracy of Screening Test for Inadequate Dietary Folate Intake Using Urinary Potassium Excretion as a Proxy...

Although folate is essential for preconception care and reproductive health, non-invasive and valid methods for screening inadequate dietary folate intake are lacking. Urinary potassium excretion, a recovery biomarker of potassium intake, can be used as a proxy for dietary folate intake if the main sources of dietary folate and potassium are the same. This study examined the accuracy of screening using urinary potassium excretion as a proxy for inadequate dietary folate intake. Participants comprised 104 female university students who completed 3-d weighed food records (3dWFR) and 24-h urine collection on the third day of 3dWFR in April-July between 2019 and 2022. The major sources of dietary folate and potassium were identified, and the correlation coefficients between their intake and urinary potassium excretion were calculated. The area under the curve (AUC) and 95% confidence interval (CI) were calculated using receiver operating characteristic analysis. Vegetables were the food groups that contributed the most to dietary folate intake (42.7%) and potassium intake (28.9%). The correlation coefficient (r=0.57, p<0.001) between dietary folate intake based on the 3dWFR and potassium excretion was almost the same as that between potassium intake and excretion (r=0.63, p<0.001). Urinary potassium excretion could discriminate at ≥100-≥550 μg in 50 μg increments for insufficient dietary folate intake with >0.7 AUC value (and >0.5 lower limit of 95% CI). These findings indicate that urinary potassium excretion can be used as a proxy indicator to screen for individuals with inadequate dietary folate intake.