Health effects of the New Nordic Renal Diet in patients with stage 3 and 4 chronic kidney disease, compared with habitual diet: a randomized trial.

BACKGROUND: Chronic kidney disease (CKD) leads to an accumulation of waste products and causes adverse cardiometabolic effects. OBJECTIVES: We investigated the health effects of the New Nordic Renal Diet (NNRD), a novel meal pattern reduced in phosphorus, protein, and sodium. METHODS: A 26-wk randomized trial compared the NNRD with a habitual diet. The NNRD group received weekly home deliveries of food and recipes. Monthly study visits included fasting blood samples, 24-h urine samples, blood pressure, and anthropometric measurements. Intention-to-treat analysis used linear mixed-effects models. RESULTS: Sixty patients, mean estimated glomerular filtration rate (eGFR) 34 mL/min/1.73 m2 and body mass index of 25-27 kg/m2, were included and 58 completed. Metabolic syndrome was present in 53% (NNRD group) and 57% (control group). The NNRD group (n = 30) reduced their 24-h urine phosphorus excretion by 19% (-153 mg; 95% confidence interval [CI]: -210, -95), control group (n = 30) (no change), between-group difference -171 mg (95% CI: -233, -109; P < 0.001). Proteinuria was reduced by 39% in the NNRD group (-0.33 g/d; 95% CI: -0.47, -0.18), control group (no change), between-group difference -0.34 g/d (95% CI: -0.52, -0.17; P < 0.001). Plasma urea was reduced by -1.5 mmol/L in the NNRD group (95% CI: -2.1, -0.9), control group (no change), between-group difference -1.4 mmol/L (95% CI: -2.0, -0.7; P < 0.001). Systolic blood pressure fell by -5.2 mmHg in the NNRD group (95% CI: -8.4, -2.1), control group (no change), between-group difference -3.9 mmHg (95% CI; -7.6, -0.2; P = 0.04). The NNRD group lost -1.7 kg (95% CI: -2.6, -0.8), control group (no change), between-group difference -2.0 kg (95% CI: -3.0, -1.0; P < 0.001). There were no effects on eGFR during the 26-wk intervention. CONCLUSION: NNRD in moderate CKD reduces phosphorus excretion, proteinuria, systolic blood pressure, and weight, mainly by reducing abdominal fat. This trial was registered at clinicaltrials.gov as NCT04579315.

Study protocol: long-term effect of the New Nordic Renal Diet on phosphorus and lipid homeostasis in patients with chronic kidney disease, stages 3 and 4: a randomised controlled trial.

INTRODUCTION: Chronic kidney disease (CKD) causes severe disturbances in phosphate metabolism. New Nordic Renal Diet (NNRD) is a new dietary concept designed by the present research group that aims to offer patients with moderate CKD a whole food approach with a markedly reduction in dietary phosphorus intake, corresponding to 850 mg/day. The present protocol describes a randomised controlled trial aiming to test the long-term effects of dietary intervention with NNRD versus a non-restricted habitual diet on important parameters of phosphorus and lipid homeostasis. METHODS AND ANALYSIS: This trial will be executed at the Department of Nephrology, Rigshospitalet, University of Copenhagen, Denmark. Sixty patients aged >18 years with CKD stages 3 and 4 (estimated glomerular filtration rate between 15 and 45 mL/min) will be recruited and randomly assigned to the intervention or control group. The other inclusion criterion includes a medically stable condition for at least 2 months prior to the start of the study. Exclusion criteria are treatment with phosphate binders, metabolic disorders that require specific dietary regulation, pregnancy and breast feeding, any types of food allergies or those who are vegans. The observation period is 26 weeks including seven study visits at the outpatient clinic combined with a weekly telephone consultation in both groups. A follow-up visit 3 months after study completion finalises the intervention. The primary outcome is the difference in the change in 24-hour urine phosphorus excretion from baseline to week 26 between the two study groups. Secondary outcomes include changes in phosphate-related and lipid metabolism-related blood and urine biochemistry, blood pressure and body composition. Moreover, we wish to explore adherence to the diet as well as quality of life. ETHICS AND DISSEMINATION: The study has been approved by the Scientific Ethical Committee of the Capital Region of Denmark and the Danish Data Protection Agency. The results of the studies will be presented at national and international scientific meetings, and publications will be submitted to peer-reviewed journals. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (wwwclinicaltrialsgov) Registry (NCT04579315). PROTOCOL VERSION: The protocol, version 2, has been approved by the Ethical Committee Denmark on 18 September 2020. The protocol has also been approved by Data Protection Regulation and Data Protection Law on 15 September 2020. This study protocol is in accordance with the Standard Protocol Items: Recommendations for International Trials.

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.