Acute effects of very-low-protein diet on FGF23 levels: a randomized study.

BACKGROUND AND OBJECTIVES High levels of fibroblast growth factor 23 are associated with mortality, CKD progression, and calcification in CKD patients. The aim of this pilot study is to assess whether a very-low-protein diet (0.3 g/kg per day) with a consequent low intake of phosphorus would reduce fibroblast growth factor 23 compared with a low-protein diet (0.6 g/kg per day) in CKD patients not yet on dialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A prospective, randomized, controlled crossover study was performed in which 32 patients were randomized into two groups. Group A (16 patients) received a very-low-protein diet (0.3 g/kg body wt per day) supplemented with ketoanalogues during the first week and a low-protein diet during the second week, and group B (16 patients) received a low-protein diet during the first week and a very-low-protein diet during the second week. Fibroblast growth factor 23, seric, and urinary phosphate levels were measured at baseline and the end of each study period. RESULTS After only 1 week of the very-low-protein diet, reductions in fibroblast growth factor 23 levels (33.5%), serum phosphate (12%), and urinary phosphate (34%) with the very-low-protein diet compared with the low-protein diet were observed. Serum and urinary phosphate levels and protein intake were significant determinants of fibroblast growth factor 23 (95% confidence interval=1.04-1.19, 1.12-1.37, and 1.51-2.23, respectively). CONCLUSIONS A very-low-protein diet supplemented with ketoanalogues reduced fibroblast growth factor 23 levels in CKD patients not yet on dialysis.