Normal levels of vitamin D are associated with less proteinuria and attenuate renal failure progression in children with chronic kidney disease (CKD), new study findings suggest.

Rukshana Shroff, MD, a pediatric nephrologist at the Great Ormond Street Hospital for Children in London, U.K., and colleagues studied 167 children with CKD (median estimated glomerular filtration rate [eGFR) 51 mL/min/1.73 m²). The cohort had a median age of 11.4 years.

The study was a post hoc analysis of the ESCAPE trial, a randomized, controlled study demonstrating that strict blood pressure (BP) control with a fixed dose of an ACE inhibitor (ramipril) shows progression of kidney disease.

At baseline, patients with the lowest 25-hydroxyvitamin D (25(OH)D) levels had the highest proteinuria levels. After ACE inhibitor treatment for a median of 8 months, those with higher 25(OH)D levels continued to have lower levels of proteinuria, the researchers reported online ahead of print in the Journal of the American Society of Nephrology.

Results also showed that lower 25(OH)D levels are positively associated with loss of eGFR. The median annualized loss of eGFR was -1.74 mL/min/1.73 m² across the study cohort. The annualized loss of eGFR was significantly greater in patients with baseline 25(OH)D levels below 50 nmol/L compared with those who had levels of 50 nmol/L or higher. The 5-year renal survival rate was 75% in patients with baseline 25(OH)D levels of 50 nmol/L or higher compared with 50% among those with lower levels, a significant between-group difference. 

The beneficial effect of 25(OH)D on renal disease progression was attenuated, but remained significant, after starting ACE inhibitor therapy: The 5-year renal survival rate was 73% in patients with 25(OH)D levels of 50 nmol/L or higher compared with 57% in patients with lower levels. The researchers defined renal survival using a composite endpoint of annualized loss of eGFR greater than 50% or progression to end-stage renal disease (eGFR less than 10 mL/min/1.73 m²) or need for renal replacement therapy. The researchers calculated that renal survival increased by 8.2% with each 10 nmol/L increase in baseline 25(OH)D.

“Vitamin D is an effective, easily available, safe, and cheap nutritional supplement that may be a useful adjunctive treatment to [renin-angiotensin-aldosterone-system] blockade to retard progressive renal function decline,” the authors concluded.

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