Many people take vitamins hoping to improve their overall health and some take them specifically to improve heart health. But research on the effects of certain vitamins on cardiovascular disease (CVD) has produced conflicting results.
Vitamins E and C are most famous for their roles as antioxidants—chemicals that soak up free radicals (substances in the body that can damage cells and lead to disease). And in some laboratory and animal studies, these vitamins have been able to suppress oxidative reactions that lead to atherogenesis, a precursor to hardening of the arteries. Multivitamins contain folic acid and B vitamins, which help keep blood levels of homocysteine in check. Elevated levels of homocysteine have been associated with an increased risk of CVD.
To bring some clarity to the role of these vitamin supplements, researchers examined a group of male physicians and found that those who took supplements of vitamins E or C, or a multivitamin did not have any lower risk of CVD than those who did not take these supplements. Their research was published in the July 8, 2002 issue of the
Archives of Internal Medicine
Researchers from several U.S. institutions and the University Hospital of Zurich, Switzerland studied a sample of men from the Physicians' Health Study—a large, ongoing trial that began in 1983. Its main goal was to study the effects of aspirin on risk of cardiovascular disease (CVD) and the effects of beta-carotene supplements on the incidence of cancer. The volunteers and the data from the Physician's Health Study have since been reviewed by other researchers to examine a variety of factors.
In this recent analysis of data from the Physician's Health Study, researchers were interested in this question: does supplementation with vitamin E, vitamin C, or multivitamins reduce the risk of dying from CVD? To find the answer, they looked at data on 83,639 of the physicians. Men were excluded from this study if they had a history of CVD or cancer (other than non-melanoma skin cancer), or if they had not provided information on vitamin supplementation on their enrollment questionnaires.
Information on supplement use was collected from the enrollment questionnaires that were completed in 1983. At this time, the physicians were healthy and between the ages of 40 and 84, with an average age of 54. Here, the physicians gave information on their use of vitamins E and C, and multivitamin supplements. This included current use, number of years taking the supplements, brands taken, and number of vitamin pills taken per week.
Researchers then checked death certificates to see which of the study volunteers died through January 31, 1988, and recorded how many of those died from CVD. They compared the death rates from CVD among those who used vitamin supplements and those who did not.
Supplements of vitamins E and C, or multivitamins did not affect the rate of death from CVD among the physicians studied. Many of the supplement users were taking high daily doses, for example 65% of those taking vitamin E took 400 IU (international units) or more per day, and only 1% reported intake of less than 100 IU per day. Among those taking vitamin C, 73% of men took an average of 500 mg or more each day. The recommended dietary allowance (RDA) for vitamin E is 22.5 IUs per day. For vitamin C, the RDA for men is 90 mg per day and for women is 75 mg per day.
During statistical analysis, the researchers adjusted for age, high blood pressure, high cholesterol, diabetes, smoking, alcohol intake, exercise, body mass index, and use of other vitamin supplements, all of which may be associated with heart disease.
Although these results are interesting and appear to bring some clarity to the role of vitamins E and C, and multivitamins in CVD risk, there are limitations of the study. First, the physicians decided whether or not to take vitamin supplements of their own accord. Those men who chose to take vitamins may have had certain characteristics that differed from men who did not take vitamins that the researchers did not account for. For example, they may have taken vitamins because they felt that their diets were lacking important nutrients—a factor that could affect their likelihood of developing CVD.
Second, data were collected solely from questionnaires done at one point in time. There was no measure of adherence to vitamin use during the study follow-up period, so it is uncertain if estimations of vitamin use based on this data reflects their true intake over time. In addition, there could have been men who originally reported not using supplements, but then began using them during the 5 1/2 years of follow-up. Another limitation associated with this self-reporting questionnaire is recall bias—the men may not have remembered correctly the exact type and dose of vitamin supplements they took.
Finally, since the volunteers for this study were healthy, well-educated, male physicians, the findings may not easily translate to other populations of people.
Should you throw out your vitamin supplements? Not necessarily. This study suggests that vitamin E and C supplements and multivitamins do not protect against CVD, but it does not give a definitive answer. Large, double-blind, randomized trials are needed to reach a more solid conclusion.
There’s certainly no harm in taking a multivitamin each day (one that provides no more than 100% of the RDAs for each nutrient) or a supplement of vitamin E or vitamin C. However, most research suggests that taking supplements does not have the same effect as eating foods that contain these vitamins. In other words, vitamin supplementation is not a reliable substitute for a healthful diet.
What can you do to reduce your risk of CVD? You can exercise regularly (with your doctor's approval), manage your stress, and eat a healthful diet—one that is rich in fruits, vegetables, legumes, and whole grains (natural sources of antioxidants) and low in total and saturated fat.