Short-term effect of the New Nordic Renal Diet on phosphorus homoeostasis in chronic kidney disease Stages 3 and 4

Background: The New Nordic Diet is a food concept favouring organically produced food items, fruits, vegetables, whole grains and fish. We investigated the short-term effects of a modified phosphorus-reduced New Nordic Renal Diet (NNRD) in chronic kidney disease (CKD) patients on important parameters of phosphorus homoeostasis. Methods: The NNRD contained a total of 850 mg phosphorus/day. A total of 18 patients, CKD Stages 3 and 4 were studied in a randomized crossover trial comparing a 1-week control period of the habitual diet with a 1-week period of the NNRD. Data were obtained at baseline and during 1 week of dietary intervention (habitual diet versus NNRD) by collecting fasting blood samples and 24-h urine collections. The primary outcome was the difference in the change in 24-h urine phosphorus excretion from baseline to Day 7 between the NNRD and habitual diet periods. Secondary outcomes were changes in the fractional excretion of phosphorus, fibroblast growth factor 23 (FGF23) and plasma phosphate. Results: As compared with the habitual diet, 24-h urine phosphorus excretion was reduced in the NNRD by 313 mg/day (P < 0.001). The mean baseline phosphorus was 875 ± 346 mg/day and was decreased by 400 ± 256 mg/day in the NNRD and 87 ± 266 mg/day in the habitual diet. The 24-h urine fractional excretion of phosphorus decreased by 11% (P < 0.001) and FGF23 decreased by 30 pg/mL (P = 0.03) with the NNRD compared with the habitual diet. Plasma phosphate did not change. Conclusion: This study demonstrates that dietary phosphorus restriction in the context of the NNRD is feasible and has positive effects on phosphorus homeostasis in CKD patients.