Study: Vitamin B may decrease kidney function in diabetic nephropathy patients

NEW YORK Patients with a kidney disease caused by diabetes that receive high-dose vitamin B therapy are more likely to have decreased kidney function and an increased risk of heart attack and stroke, a new study found.

Published in the Apr. 28 issue of the Journal of the American Medical Association, Andrew House, M.D., of the University of Western Ontario, and J. David Spence, M.D., of the Robarts Research Institute, London, Ontario, and colleagues conducted a study to examine whether B-vitamin therapy would slow the progression of diabetic nephropathy and prevent vascular events in 238 patients with Type 1 or 2 diabetes. Data taken from patients in the randomized, placebo-controlled trial between May 2001 and May 2007 found the measure of kidney function -- radionuclide glomerular filtration rate, or GFR -- rapidly decreased in those who consumed vitamin B6 and B12, between baseline and 36 months, compared with the placebo group. Additionally, the researchers found that risk of such cardiovascular events as heart attack, stroke, revascularization, and all-cause mortality, doubled in the B-vitamin group.

Meanwhile, House, Spence and colleagues also added that they tested the patients' levels of homocysteine, a naturally occurring amino acid found in blood plasma. While high levels of homocysteine are more likely to cause heart attack and other diseases, the researchers noted that participants in the B-vitamin group had an average decrease while participants in the placebo group had an average increase. This result, the authors concluded, should not necessarily be a guide for those interested in testing this theory outside of a clinical trial.

"Given the recent large-scale clinical trials showing no treatment benefit, and our trial demonstrating harm, it would be prudent to discourage the use of high-dose B vitamins as a homocysteine-lowering strategy outside the framework of properly conducted clinical research," the authors concluded.

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