Research warns against common diabetes treatment


By Heather Travis
Thursday, April 29, 2010
Diabetics with kidney failure taking high doses of B vitamins need to stop taking this prescriptive therapy because it doubles their risk for heart attacks and strokes.
Dr. David Spence, director of Robarts’ Research Institute’s Stroke Prevention and Atherosclerosis Research Centre, is encouraging people with diabetes taking high doses of B vitamins to stop their treatment because it increases risks for heart attacks or strokes. These surprising results are published in a study Wednesday in the Journal of the American Medical Association.
This no-nonsense message comes from Dr. David Spence, director of Robarts’ Research Institute’s Stroke Prevention and Atherosclerosis Research Centre and corresponding author of a shocking study that challenges the use of a commonly prescribed therapy for diabetic patients.
“People with renal failure shouldn’t be using these high doses of vitamins and we need to be looking into alternatives,” says Spence. “People tend to think vitamins are innocuous, but we’ve known for ages that high doses of vitamins can be harmful.”
The study examined the effects of vitamin B therapy on diabetic nephropathy, which is kidney disease or damage that is a complication of diabetes. It was published in the April 28 edition of the Journal of the American Medical Association.  
More than three million Canadians have diabetes (21 million Americans), and more than 40 per cent of people with diabetes will develop nephropathy.  
Spence and his colleagues began their study of people with kidney disease anticipating people who received high-dose vitamin B therapy (folic acid, vitamin B6 and vitamin B12) would have improved kidney function and fewer heart attacks and stroke, compared with those on placebos.  
The opposite was true. Those receiving high dose vitamin B therapy had significantly greater worsening of kidney function. They also had twice as many heart and stroke incidents.  
“What we found, to our great surprise, was that vitamin therapy actually seemed to make the decline of kidney function worse,” he says. “Even more surprising and concerning was there was a significantly higher rate of heart attacks and strokes among the people who were assigned high dose vitamins.
“What this means is we shouldn’t be using high-dose vitamins to lower homocysteine levels in people with kidney failure.”  
Diabetics tend to have higher levels of homocysteine, an amino acid that increases clotting of the blood. Studies have shown that too much homocysteine in the blood is related to a higher risk of coronary heart disease, stroke and peripheral vascular disease.  
As predicted in the study, homocysteine levels in those on vitamin B therapy were lowered, but this benefit doesn’t outweigh the increased risk for heart attacks and strokes.
The research was conducted at five university medical centres by Spence and his colleagues in the Department of Medicine at Western’s Schulich School of Medicine & Dentistry, Dr. Andrew House and Dr. George Dresser, and by researchers at the University of Calgary, University of Toronto, McMaster University and the University of Manitoba.
The B vitamins are water soluble and the excess vitamins are normally eliminated from the body in urine. But it is believed people with kidney failure taking high doses of B vitamins build up toxic levels because of their inability to flush the excess from their systems.
“We are going to have to look for other approaches to lowering homocysteine levels,” says Spence, noting research is underway at Western to examine effective alternatives.
This is the first study to show the B vitamins are harmful for people with kidney damage.
Vitamin B therapy may still be beneficial in people with normal kidney function.
The study was funded by the Canadian Institutes of Health Research.  Spence, Dresser and House, are also scientists with the Lawson Health Research Institute.      

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