Do Antioxidants Contribute to Heart Disease?
Study Shows Vitamins Raise Levels of Bad Cholesterol in Mice
WebMD News Archive
May 3, 2004 --Taking antioxidant vitamins, a practice done daily by millions of Americans in hopes of preventing heart disease, may actually contribute to it by boosting production of "bad" cholesterol.
New research on rodents shows that high doses of the much ballyhooed antioxidant nutrients -- vitamins C, E, and beta-carotene -- stimulate their liver's production of very low density lipoproteins (VLDL), which convert in the bloodstream to low-density lipoprotein (LDL), the so-called "bad" cholesterol that accumulates along artery walls and leads to atherosclerosis, or hardening of the arteries.
This suggests that getting doses of antioxidants usually found in vitamin supplements -- but not what is found in food -- may be "potentially harmful" for the heart, says researcher Edward A. Fisher, MD, PhD, director of the Lipid Treatment and Research Center at New York University Medical Center.
"If you're concerned about heart disease, our study offers another reason not to take them," he tells WebMD. "But it's not as simple as whether you should take, or not take, vitamin E or other antioxidants. What our study shows is that in some situations, oxidative stress might be good and in others it is bad."
Until now, "oxidative stress" was considered to be all bad -- the process in which "free radicals," or unstable molecules, damages cells and contribute to scores of disease.
Antioxidants prevent oxidative stress and have been thought to help reduce risk of cancer, diabetes, Alzheimer's disease, and other conditions. This is one reason why fruits and vegetables, which are generally rich sources of these nutrients, are universally recommended. But the role of higher-dose vitamin supplements is less established, particularly in preventing heart disease.
Some studies show that antioxidant supplements are helpful. Antioxidants are thought to prevent the changes that turn cholesterol molecules in the blood into substances that can form plaques in artery walls, blocking blood flow. But other studies indicate these supplements may be wasted money because they offer no benefit -- and may even boost heart disease risk.
Antioxidants Boost LDL Cholesterol
In his study, Fisher's team found that vitamin E, a well-known antioxidant, prevented the normal breakdown of fats in rat and mouse liver cells. In other words, these antioxidants prevented the liver from destroying fats such as VLDL, the precursor to "bad" LDL cholesterol. The antioxidants caused more VLDL to be present.
His research, published in the Journal of Clinical Investigation, is reportedly the first to link antioxidant vitamins with increased VLDL production. And that's what it makes it important, says one expert.
"The bottom line of this paper is that you shouldn't assume that taking antioxidant vitamins is only going to have beneficial effects on cardiovascular disease," says Ronald M. Krauss, MD, director of atherosclerosis research at Children's Hospital Oakland Research Institute, who was not involved in Fisher's study but wrote an accompanying editorial to it.