THURSDAY, Aug. 9, 2001 (HealthDayNews) -- Heart patients should keep the lid on their vitamin bottles, say doctors who find that antioxidants like E, C, beta-carotene and selenium blunt the effects of common cholesterol-lowering drugs.
Ordinarily, the drugs raise the level of "good" blood cholesterol, called high density lipids (HDL), which helps sweep away the "sticky" cholesterol that can clog arteries. But when heart patients took the drugs with antioxidants, the good effect was dampened considerably.
University of Washington scientists were surprised at their finding. When they started the study, they were hoping to multiply HDL levels in heart patients by adding antioxidants to their medicines. Instead, they found the vitamins negated the drugs' effects. Antioxidants in the diet have been widely touted for reducing the risk of coronary artery disease, but several studies have found they have no effect on the disease.
"All the good effect [of increasing HDL levels] is wiped out. We did not expect that result," says associate professor Marian C. Cheung, lead author of the study, which appears in the August Atherosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.
Cheung analyzed the results of a year-long study that included a group of heart patients who took only drugs to lower their cholesterol and another group of patients who took drugs with antioxidants for the same purpose. She found overall cholesterol levels were reduced by about 25 percent in both groups. Patients taking the drugs alone also had a 25 percent increase in HDL levels while those taking the drug/antioxidant combination only had an 18 percent increase in HDL. More dramatically, the part of the good cholesterol known as HDL(2), which is most responsible for protecting against heart disease, increased 42 percent among patients who took only the drugs, but didn't change in people who took the drug/antioxidant combination.
"This is the first time that we've shown that over-the-counter antioxidant vitamins so commonly used in the United States can actually nullify the effects of these cholesterol drugs," she says. "We had a small number of subjects, but when the results are so consistent, going from over 40 percent to zero, that is a strong [result]."
The study used simvastatin, one of the family of drugs called statins that lowers LDL, or "bad" cholesterol, and the B vitamin niacin, which was considered a drug for purposes of the study and which usually increases HDL levels by at least 20 percent, Cheung says. She had hoped that combining the drugs would "get twice the benefit" for heart patients.
University of Pittsburgh epidemiologist Dr. Lewis H. Kuller, in an editorial accompanying the study, recommends caution in taking antioxidants with heart drugs.
"Just taking a multi-vitamin pill daily is probably no problem, but don't take vitamin E or antioxidant supplements until results of new trials are in. There is no evidence of good effect and potential evidence of harm. This is not a neutral effect," he says.
"Why horse around with [antioxidants] when you have such potent therapies that work?" he says.
The American Heart Association (AHA) has not recommended antioxidant vitamins to reduce risk of coronary heart disease because of the lack of consistent evidence of benefits, says AHA spokesman Dr. Ronald Krauss of the University of California at Berkeley.
"The observation of a lowering of HDL in statin-treated patients by an antioxidant cocktail raises a caution, but it will be necessary to confirm this observation, preferably with studies of individual antioxidants, before we can conclude that any of these are harmful," he says.
The study included 135 men and 18 women, ages 33 to 74, who had heart disease and low HDL levels. They were divided into four groups: those given the drug simvastatin (marketed as Zocor) with niacin; those given the four antioxidant supplements of vitamins E, C, beta carotene and selenium; those given a combination of the drugs and the vitamin supplements, and those in a control group given nothing but sugar pills.
The study also found that antioxidant supplements alone had no effect on HDL or other cholesterol levels.
"In animal studies of rabbits and mice, antioxidants have been shown to be beneficial to HDL levels," but the effect did not carry over to humans, Cheung says.
The study did not address which, or what combination of antioxidants might be damping the effects of the drugs, nor how each supplement reacted with the two different drugs.
The study was funded by the National Institutes of Health and the medications used in the study were provided by the pharmaceutical companies Merck and Co., based in Whitehouse Station, N.J., and Upsher-Smith Laboratories, based in Minneapolis.
What To Do
The study was small, but the results make a compelling case for talking to your doctor about taking antioxidant vitamins if you also are taking cholesterol drugs.
For more information about cholesterol and an explanation of LDL and HDL, go to the National Institutes of Health. For the AHA's position on vitamin supplements, click here.
