Doubt over use of antioxidant vitamins for the prevention of coronary disease
Graham McKerrow, HIV i-Base
A study of patients at high risk of a major cardiac event has found that combination treatment with simvastatin and niacin can reduce the risk factors associated with myocardial infarction by 60 to 90%.
The research at the University of Washington at Seattle also found that the practice of using antioxidant vitamins, recommended by many physicians, could make the lipid lowering drugs less effective.
The lead author of the research, Dr B Greg Brown, says his advice is now the opposite of what it used to be. Following the study, he says physicians should discourage their patients from taking antioxidant vitamins, such as vitamin E, vitamin C and b carotene. He now believes these vitamins limit the rise in high density lipoprotein (HDL) cholesterol experienced by patients taking the simvastatin and niacin combination.
Until now, both lipid-modifying therapy and antioxidant vitamins were thought to benefit patients with coronary disease. The researchers looked at simvastatin-niacin and antioxidant vitamin therapy, alone and together.
The three year, double blind trial studied 160 patients in Canada and the Seattle area who had clinical coronary disease and low levels of HDL cholesterol and normal levels of low density lipoprotein (LDL) cholesterol. They were randomly assigned to receive one of four regimens: simvastatin plus niacin, antioxidants, simvastatin plus niacin plus antioxidants, or placebos. All received counselling regarding lifestyle changes such as losing weight, consumption of monounsaturated fats, giving up smoking and taking regular exercise.
At the beginning and end of the study angiography was used to assess the build up of plaque. People in the group receiving simvastatin and niacin had coronary arteries that were less blocked than those of people in the other groups. The mean levels of LDL and HDL cholesterol were unaltered in the antioxidant group and the placebo group; but these levels changed substantially in the simvastatin-niacin group, which saw the mean LDL level drop by 42% and the mean HDL level rise by 26%.
On average, proximal coronary stenosis regressed slightly in patients in the simvastatin-niacin group and the rate of major clinical events in that group was 90 per cent lower than in the placebo group. Conversely the research found “no significant benefits” from the relatively high dose regimen of four antioxidant agents. When antioxidants were combined with simvastatin and niacin, arterial and clinical benefits “tended to diminish” as compared with those achieved with simvastatin and niacin alone.
The researchers conclude, in their paper published in the New England Journal of Medicine, that: “Simvastatin plus niacin provides marked clinical and angiographically measurable benefits in patients with coronary disease and low HDL levels. The use of antioxidant vitamins in this setting must be questioned.”
Brown BG, Zhao XQ, Chait A et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001 Nov 29;345(22):1583-92.