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Vitamin B Therapy May Be Unsafe in Diabetic Nephropathy

High doses associated with greater decrease in renal function, increase in stroke, heart attack

TUESDAY, April 27 (HealthDay News) -- Patients with diabetic nephropathy who take high doses of vitamin B may experience a greater decrease in glomerular filtration rate (GFR) than those on placebo, as well as an increase in vascular events, according to research published in the April 28 issue of the Journal of the American Medical Association.

Andrew A. House, M.D., of the University of Western Ontario in London, Canada, and colleagues randomized 238 subjects with type 1 or type 2 diabetes and diabetic nephropathy to receive either placebo or a tablet of B vitamins containing vitamin B6, vitamin B12 and folic acid to test the hypothesis that B-vitamin therapy can slow the progression of diabetic nephropathy and prevent vascular complications.

The researchers found that, at 36 months, radionuclide GFR had decreased more in the B-vitamin group than in the control group: mean 16.5 (1.7) mL/min/1.73 m2 versus 10.7 (1.7) mL/min/1.73 m2. There was no difference in dialysis required. The composite outcome (stroke, myocardial infarction, revascularization and all-cause mortality) happened more in the B-vitamin group (hazard ratio, 2.0), and plasma total homocysteine decreased by a mean 2.2 (0.4) µmol/L in the B-vitamin group but increased by a mean of 2.6 (0.4) µmol/L in the placebo group.

"In our randomized trial, the use of high doses of B vitamins compared with placebo resulted in a greater decrease in GFR and an increase in myocardial infarction and stroke. 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 write.

Pan American Laboratories provided B-vitamins and placebo in-kind for the study, and one author disclosed financial ties to Pan American and Medice Arzneimittel Putter GmbH & Co. Two authors have a patent pending on use of mesna to reduce homocysteine levels in patients on dialysis.

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