A Downside to Antioxidants
Antioxidants, which have been trumpeted as wonder vitamins on product labels from skin treatments to tomato juice, may actually be harmful for people taking cholesterol-lowering drugs, according to new research released Thursday.
Tens of millions of Americans take supplements that include antioxidants--a category that includes Vitamin C, Vitamin E, beta-carotene and selenium. A recent survey by Prevention magazine suggested the number of people taking the supplements may be as high as 80 million.
Since the early 1990s, some doctors have recommended vitamin supplements as one arm of a strategy to combat heart disease. The recommendation stemmed from a study showing that people who took high doses of Vitamin E suffered 30% fewer heart attacks than those who did not.
But the new research shows that antioxidant vitamins like Vitamin E and beta-carotene “just haven’t cut the mustard,” says Dr. B. Greg Brown, an author of the study. In fact, he added, patients who attempt to manage their heart disease with antioxidant vitamins “are actually doing themselves a disservice.”
Dr. Lewis H. Kuller, a University of Pittsburgh physician not involved in the study, agrees: “We have a lot of very good therapies for preventing heart disease, and people should stick to those.”
The American Heart Assn., which published the new research in its journal Atherosclerosis, Thrombosis, and Vascular Biology, recommends that people not take any vitamin supplements, including antioxidants, and that they instead get all their nutrients from a balanced diet.
The new study, conducted at the University of Washington, followed 153 patients with coronary artery disease for one year as they underwent therapy with cholesterol-lowering drugs, antioxidant vitamin supplements, a combination of both, or a placebo. Patients who received the antioxidants took a dose commonly found in vitamin supplements sold over the counter.
One aim of the cholesterol-lowering drugs is to increase the level of high-density lipoprotein, the so-called “good cholesterol,” in a patient’s blood. As expected, people taking the cholesterol-lowering drugs enjoyed a rise in HDL levels. But when the drugs were combined with antioxidant therapy, the beneficial effects were blunted. Patients who took only the antioxidant supplements experienced no improvement in cholesterol levels.
The most dramatic effect of the antioxidants was seen when researcher Marian Cheung and her colleagues measured the levels of HDL-2, the specific form of cholesterol that provides the greatest benefits to patients with heart disease. The cholesterol-lowering drugs raised HDL-2 levels by 42%, but when the antioxidants were added to the drug therapy, there was no increase in HDL-2.
All of the patients were counseled in “lifestyle modification” to improve diet, increase exercise and stop smoking.
Coronary artery disease is thought to be caused by the buildup of fatty plaques on artery walls, diminishing the blood supply to the heart muscle. Physicians believe that cholesterol--particularly LDL, or “bad cholesterol”--is a primary factor in the disease.
The reason researchers thought that antioxidants might be helpful is that when LDL becomes oxidized, it can more easily become part of the fatty plaques. The authors of the new study had thought the vitamin supplements’ antioxidant effects would help to combat the oxidation of LDL. But while the antioxidants do reduce oxidation of LDL, they are apparently detrimental to the production of HDL-2. The interference of the antioxidants with the drugs’ beneficial effects was “a very big surprise,” Cheung said.
Other recent clinical studies, which together involved more than 60,000 patients, have shown that antioxidants are not beneficial to those with heart disease. This is the first study, however, to measure changes in the specific forms of cholesterol in the blood. The results give researchers a more detailed picture of how antioxidants act in the body.
