Source-Dependent Renal Effects of Commercial Protein Supplements: A 28-Day Study in Rats

Background and Objectives: Commercial protein powders are widely consumed to increase dietary protein intake, yet whether their renal effects differ by protein source remains poorly characterized. The primary objective of this study was therefore to determine whether 28 days of administration of commercial whey, casein, soy or beef protein powder produces source-dependent renal histopathological injury in rats, with the total renal injury score as the primary outcome. Secondary objectives were to assess conventional renal function markers and the renal oxidative stress response. Materials and Methods: Thirty-five female Sprague Dawley rats were stratified by body weight and randomly assigned to five groups (n = 7 per group): control, whey, casein, soy and beef. The powders were given by oral gavage in 0.9% sterile isotonic saline at 400 mg/kg/day of protein for 28 consecutive days; controls received the vehicle only. Body weight, kidney-to-body weight ratio, serum urea and creatinine, urinalysis, renal histopathology, renal oxidative stress parameters and the elemental composition of the powders were assessed.