Vitamin B therapy can worsen diabetic nephropathy symptoms
MedWire News: High doses of vitamin B, prescribed to reduce levels of homocysteine, accelerate the progression of diabetic nephropathy, report researchers.
They add that cardiovascular (CV) events such as myocardial infarction (MI) and stroke are also increased in patients taking B vitamins compared with placebo.
Several observational studies have suggested that high homocysteine levels can increase the risk for diabetic nephropathy, retinopathy, and vascular disease, therefore vitamin B has been suggested as a possible treatment for lowering the concentration of homocysteine in diabetics, explain J David Spence (Robarts Research Institute, London, Ontario, Canada) and colleagues.
To test this, the investigators recruited 238 Type 1 and Type 2 diabetic patients with diabetic nephropathy, a precursor to chronic kidney disease (CKD), to take part in the DIVINe (Diabetic Intervention with Vitamins to Improve Nephropathy) study.
The patients were randomly assigned in a 1:1 fashion to take a single combined B vitamin tablet (folic acid 2.5 mg, vitamin B6 25 mg, and vitamin B12 1 mg) or placebo, once daily between May 2001 and July 2007. The mean follow-up period was 31.9 months.
Writing in the Journal of the American Medical Association, the authors report that the radionuclide glomerular filtration rate (GFR) decreased more in the B vitamin than the placebo group, by a mean of 16.5 versus 10.7 ml/min/1.73 m2 by the end of follow-up.
Dialysis requirement did not significantly differ between the two groups at study completion. However, twice as many people in the B vitamin group had experienced the composite CV outcome of MI, stroke, revascularization, or all-cause mortality as those in the placebo group, a significant difference.
"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 conclude.
“Because B vitamins are water soluble, we suspect that while healthy people would excrete excess vitamins in urine, those with renal failure would not be able to do so, perhaps causing the adverse affects we have seen in this study,” added Spence.
He said: “Vitamin B therapy may still be beneficial in people with normal kidney function, but this is clear evidence that high doses of vitamin B should not be given to those with kidney problems.”
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By Helen Albert