Dietary Sodium to Potassium Ratio and the Incidence of Chronic Kidney Disease in Adults : A Longitudinal Follow-Up Study

Abstract

The aim of this study was to explore the association of dietary sodium to potassium (Na/K) ratio and the risk of chronic kidney disease (CKD) in general Iranian adults. In this prospective cohort study, 1,780 adults, free of baseline CKD with complete follow-up data, were selected from among participants of the Tehran Lipid and Glucose Study and followed for 6.3 years for development of CKD. Dietary sodium and potassium were assessed using a valid and reliable 168-item food frequency questionnaire. Estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease Study equation, and CKD was defined as eGFR <60 mL/min/1.73 m2. Mean dietary intakes of sodium and potassium were 4,547±3,703 and 3,753±1,485 mg/d, respectively, and their ratio was 1.35±1.29. No significant association was found between dietary intakes of sodium and potassium and the risk of CKD after 6.3 y of follow-up, whereas in the case of dietary Na/K ratio, participants in the highest compared to lowest tertile (2.43 vs 1.61) had a significantly increased risk of CKD (odds ratio=1.52, 95% confidence interval=1.01~2.30); an increasing trend in the risk of CKD across tertiles of dietary sodium to potassium ratio was also observed (P for trend=0.05). Present findings demonstrate that the dietary Na/K ratio is a stronger predictor of CKD than the dietary sodium or potassium per se. Decreased dietary Na/K ratio may be considered as an effective dietary approach to modify the risk of kidney dysfunction.

Science of Salt: A regularly updated systematic review of salt and health outcomes studies (April to October 2018)

“…The weekly search identified 4141 citations over the period from April 3 to October 30, 2018, of which 19 studies including dietary sodium and health outcomes met the criteria for full review (Table ). These included systematic review and meta‐analyses (n = 2), randomized controlled trials (n = 3, including one post hoc analysis of a randomized controlled trial), a non‐randomized controlled trial (n = 1), prospective cohort studies (n = 4), a retrospective cohort study using population data (n = 1), and cross‐sectional studies (n = 8) . Two studies assessed mortality outcomes, four studies assessed morbidity outcomes, and one study assessed symptoms/quality of life/functional status outcomes .…”

“…Of greater concern is the proportional bias that exists whereby the level of over‐ or under‐estimation is proportional to mean sodium excretion. Two cohort studies included in this review used FFQ to assess the association between sodium intake at baseline and incidence of chronic kidney disease among people with normal kidney function in Korea and Iran . A recent review found that FFQs are not adequate for quantifying sodium intake in individuals .…”

“…Two cohort studies included in this review used FFQ to assess the association between sodium intake at baseline and incidence of chronic kidney disease among people with normal kidney function in Korea 31 and Iran. 30 A recent review found that FFQs are not adequate for quantifying sodium intake in individuals. 53 Although dietary assessment methods are necessary in people with established CKD (in whom urinary excretion is impaired), both these studies included only people with normal renal function at baseline and so multiple 24-hour urine collections would have been a more accurate measure of usual intake.…”

“…These included systematic review and meta-analyses (n = 2), 22,23 randomized controlled trials (n = 3, including one post hoc analysis of a randomized controlled trial), [24][25][26] a non-randomized controlled trial (n = 1), 27 prospective cohort studies (n = 4), [28][29][30][31] a retrospective cohort study using population data (n = 1), 32 and cross-sectional studies (n = 8). [33][34][35][36][37][38][39][40] Two studies assessed mortality outcomes, 28,29 four studies assessed morbidity outcomes, [30][31][32][33] and one study assessed symptoms/quality of life/functional status outcomes. 22 Eight studies assessed clinical surrogate outcomes, [23][24][25][26][27][34][35][36] one study assessed physiologic surrogate outcomes, 37 and three studies assessed other outcomes [38][39][40] according to our pre-specified categories.…”

Comparison of 24-h Diet Records, 24-h Urine, and Duplicate Diets for Estimating Dietary Intakes of Potassium, Sodium, and Iodine in Children

“…In addition, a high dietary intake of potassium may mitigate the negative consequences of high sodium consumption. A lower ratio of sodium to potassium has been linked to a reduced risk for obesity, cardiovascular disease, and chronic kidney disease [4,10,[13][14][15][16].…”