Pistachio Consumption in Patients With Chronic Kidney Disease

Standard chronic kidney disease (CKD) guidelines frequently restrict nut intake due to concerns regarding their phosphorus and potassium content. While uncontrolled phosphorus loading exacerbates secondary hyperparathyroidism, vascular calcification, and mortality, overly restrictive diets can preclude the intake of essential cardioprotective nutrients. Phytate (myo-inositol hexaphosphate), abundant in fiber-rich foods like pistachios, acts as a natural inhibitor of calcium salt deposition, potentially mitigating vascular calcification. Crucially, the phosphorus in nuts is largely organically bound as phytate, which resists enzymatic cleavage in the human gastrointestinal tract, significantly reducing its intestinal bioavailability. Given these properties, moderate pistachio consumption may offer cardiovascular benefits without compromising mineral metabolism. This study aims to evaluate the short-term effects of pistachio supplementation on circulating and urinary phosphorus, parathyroid hormone (PTH) in patients with CKD. This study is an open-label, randomized, controlled crossover clinical trial involving patients with stage 4 and 5 (non-dialysis) CKD. All participants will undergo a 1-week run-in period to initiate a standardized pre-dialysis renal diet (protein 0.8 g/kg/day, potassium 39 mg/kg/day, phosphorus 12 mg/kg/day). Following the run-in, participants will be randomized (1:1 ratio) to one of two 4-week dietary sequences of Pistachio Diet period (30 g/day of pistachios) or Control Diet period. The sequences will be separated by a 4-week washout period. Venous blood and 24-hour urine samples will be collected and serum biomarkers: Phosphorus, potassium, PTH, FGF23, MDA, fasting glucose, creatinine, lipid profile, high-sensitivity C-reactive protein (CRP), and alkaline phosphatase and urinary phosphorus, sodium, uric acid, and potassium will be measured.