Do Antioxidants Contribute to Heart Disease?
Study Shows Vitamins Raise Levels of Bad Cholesterol in Mice
Antioxidants Boost LDL Cholesterol continued...
"There is no human clinical information -- the research was done on animals -- so this study doesn't offer a recommendation of whether or not you should take antioxidant vitamins," Krauss tells WebMD. "But it provides good background into what may be occurring when one does take antioxidants and help explain some previous findings."
Two years ago, a study of 20,000 people -- already with heart disease risks such as diabetes or blood vessel damage -- showed that taking daily supplements of vitamins C, E, and beta-carotene produced small but noticeable increases in heart disease risk factors such as higher levels of LDL cholesterol and triglycerides, a blood fat linked to heart disease. This study also linked these supplements to lower levels of "good" HDL cholesterol.
"The changes experienced were modest but consistent with mechanisms identified in this paper," Krauss tells WebMD. He says a previous study showed that giving an antioxidant cocktail to people with heart disease reduced the benefits of some cholesterol-lowering drugs.
Last June, after reviewing 15 previous studies involving more than 15,000 people, Cleveland Clinic researchers reported in The Lancet that taking vitamin E did not help prevent heart disease and that taking high levels of beta-carotene supplement actually caused a slight increase in risk of heart attack or stroke. Two weeks later, the U.S. Preventive Services Task Force published its own paper in Annals of Internal Medicine showing there was no evidence that antioxidants, or folic acid, protected against heart disease -- and the agency even warned against taking beta-carotene supplements, which have previously been linked to increased lung cancer risk in smokers.
Does this mean that antioxidant supplements should be avoided? Not necessarily, says Krauss.
"There is evidence that supplements are beneficial for other conditions. And there is the suggestion that if you start taking them early in life, before atherosclerosis develops or there are significant signs of heart disease, these vitamins might be protective, rather than waiting until the disease has come into the picture. What this study shows is that despite popular belief that antioxidants are all good, they might have their downside as well, at least as it pertains to heart disease."