Health News

Vitamin D for Kidney Disease Unproven

Dec. 17, 2007 -- Vitamin D compounds, routinely given to patients with chronic kidney disease to help preserve their bones, are not proven scientifically to help, according to a new report.

Researchers evaluated 76 published trials on vitamin D compounds, performing what is known as a meta-analysis, in which the results of several studies are combined.

Bottom line: "Despite many years of use, this is an intervention ... of unproven efficacy when it comes to achieving what really matters -- that is, a reduction in deaths, fractures, and cardiovascular events," says Giovanni Strippoli, MD, research coordinator at the Mario Negri Sud Consortium in Italy and a co-author of the study.

The Problem

In chronic kidney disease, caused by such conditions as high blood pressure and diabetes, the organs do not work properly and can eventually fail, leading to a need for dialysis.

Chronic kidney disease patients are often deficient in vitamin D, which helps maintain normal blood levels of calcium and phosphorous and helps promote calcium absorption, important for strong bones.

Diseased kidneys can't remove excess phosphorous found in foods as normal kidneys do. As phosphorous builds up, calcium in the blood drops. Then four small glands in the neck, called the parathyroid glands, become too active and too much calcium is removed from the bones, causing them to weaken and possibly fracture, according to the National Kidney Foundation.

When parathyroid hormone, as well as blood levels of phosphorous and calcium, builds up to excess, the risk of bone fractures, disability, and death increase.

To remedy the problem, doctors generally advise eating a low-phosphorous diet and taking one of a variety of medicines with a form of vitamin D and other components, either orally or injectables.

"Vitamin D compounds have been used for over 30 years and are very widespread," Suetonia Palmer, MBChB, a clinical research training fellow at the University of Otago, New Zealand, tells WebMD. "However, their effect on mortality and cardiovascular health remains unknown."