Vitamin D for Kidney Disease Unproven
Review of 76 Studies Shows Value of Vitamin D Treatment for Chronic Kidney Disease 'Uncertain'
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
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.
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
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."