Higher doses of vitamin D than are currently recommended in guidelines may be necessary to lower fracture risk in renal transplant recipients, according to study findings presented at the 56th European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Congress in Budapest, Hungary.

KDIGO (Kidney Disease: Improving Global Outcome) guidelines recommend correction of vitamin D deficiency or insufficiency to improve bone health based on a guidelines for the general population, but high-grade evidence supporting this recommendation has been lacking, according to information provided in an ERA-EDTA press release.

In a prospective, multicenter, double-blind controlled trial, a team led by Marie Courbebaisse, MD, PhD, of Hôpital Européen Georges-Pompidou in Paris, assigned 536 kidney transplant recipients to receive either 12,000 IU (low dose) or 100,000 IU cholecalciferol (high dose) every 2 weeks for 2 months, then monthly for 22 months. In the study, a low dose corresponded to a minimum recommended intake of 400 IU per day.

At 24 months, vitamin D levels were significantly higher in the high-dose (43.1 vs 25.1 ng/mL at study inclusion) than in the low-dose group (25.1 vs 20.2 ng/mL at study inclusion). The incidence of fractures was significantly lower in the high-dose than low-dose group (1% vs 4%). The investigators observed no differences between the groups in the risks of diabetes, major cardiac events, new cancers, or death. High-dose cholecalciferol was well tolerated, with no increased risks of vascular calcification or hypercalcemia or hyperphosphatemia.

“Our study shows that currently recommended doses of vitamin D are not sufficient to protect patients from the risk of fracture after kidney transplantation,” Dr Courbebaisse said in the press release. “This challenges advice in the current international KDIGO guidelines, which recommend using low doses of cholecalciferol similar to those recommended for the general population.”

Commenting on the study, ERA-EDTA President Carmine Zoccali, MD, said: “The VITALE trial is important because it show that high-dose vitamin D is an effective way of lowering the rate of fractures after kidney transplantation, with a very low risk of any side effects. More broadly, we see yet again that other benefits for vitamin D seen in observational studies are not reflected when supplementation is tested in randomized controlled trials.”