Concordance of dietary sodium intake and concomitant phosphate load: Implications for sodium interventions.
Both a high dietary sodium and high phosphate load are associated with an increased cardiovascular risk in patients with chronic kidney disease (CKD), and possibly also in non-CKD populations. Sodium and phosphate are abundantly present in processed food. We hypothesized that (modulation of) dietary sodium is accompanied by changes in phosphate load across populations with normal and impaired renal function.



We first investigated the association between sodium and phosphate load in 24-h urine samples from healthy controls (n = 252), patients with type 2 diabetes mellitus (DM, n = 255) and renal transplant recipients (RTR, n = 705). Secondly, we assessed the effect of sodium restriction on phosphate excretion in a nondiabetic CKD cohort (ND-CKD: n = 43) and a diabetic CKD cohort (D-CKD: n = 39). Sodium excretion correlated with phosphate excretion in healthy controls (R = 0.386, P < 0.001), DM (R = 0.490, P < 0.001), and RTR (R = 0.519, P < 0.001). This correlation was also present during regular sodium intake in the intervention studies (ND-CKD: R = 0.491, P < 0.001; D-CKD: R = 0.729, P < 0.001). In multivariable regression analysis, sodium excretion remained significantly correlated with phosphate excretion after adjustment for age, gender, BMI, and eGFR in all observational cohorts. In ND-CKD and D-CKD moderate sodium restriction reduced phosphate excretion (31 ± 10 to 28 ± 10 mmol/d; P = 0.04 and 26 ± 11 to 23 ± 9 mmol/d; P = 0.02 respectively).



Dietary exposure to sodium and phosphate are correlated across the spectrum of renal function impairment. The concomitant reduction in phosphate intake accompanying sodium restriction underlines the off-target effects on other nutritional components, which may contribute to the beneficial cardiovascular effects of sodium restriction. (f) Registration numbers: Dutch Trial Register NTR675, NTR2366.
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
J K
JK
Humalda
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Department of Internal Medicine, Division of Nephrology, ZGT Hospital Almelo, The Netherlands.
C A
CA
Keyzer
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
S H
SH
Binnenmars
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
A J
AJ
Kwakernaak
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
M C J
MC
Slagman
Department of Internal Medicine, Division of Nephrology, ZGT Hospital Almelo, The Netherlands.
G D
GD
Laverman
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
S J L
SJ
Bakker
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
M H
MH
de Borst
Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Electronic address: g.j.navis@umcg.nl.
G J
GJ
Navis
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003928:Diabetic Nephropathies / Q000178:diet therapy* / Q000209:etiology / Q000503:physiopathology / Q000652:urine; D004039:Diet, Sodium-Restricted; D057140:Fast Foods / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010710:Phosphates / Q000009:adverse effects* / Q000652:urine; D016226:Phosphorus, Dietary / Q000009:adverse effects* / Q000652:urine; D011446:Prospective Studies; D064167:Recommended Dietary Allowances; D065667:Renal Elimination; D051436:Renal Insufficiency, Chronic / Q000178:diet therapy* / Q000209:etiology / Q000503:physiopathology / Q000652:urine; D012982:Sodium, Dietary / Q000009:adverse effects* / Q000652:urine; D013997:Time Factors; D016896:Treatment Outcome
D010710:Phosphates; D016226:Phosphorus, Dietary; D012982:Sodium, Dietary
Dietary counseling; Excretion; Phosphate; Sodium