People take large doses of vitamin E in the belief that it helps counter oxidation by unstable 'free radical' molecules, which damages cells and can accelerate aging and lead to heart disease and cancer.
Miller, who was surprised by the findings of the study, said there could be several ways the vitamin supplementation is damaging the body.
While vitamin E in low doses is a powerful antioxidant, in higher doses its effects may promote oxidative damage, and may also overwhelm the body's natural antioxidants, he said.
Dr. Raymond Gibbons of the Mayo Clinic in Rochester, Minnesota, said the evidence has been building against vitamin E supplements.
'Despite this ... I see many, many patients still taking vitamin E and I have to convince them not to,' he told a separate news conference.
I think there's a sneaking suspicion that humans in wealthy nations probably make a pretty optimal use of key nutrients. The only dietary ways to extend life are likely to be calorie restriction and maybe fat restrictions. What helps in one regard may hurt in another. Disappointingly similar to medications, but unlikely to affect supplement sales.