Dr. Marla Shapiro: Multivitamins and heart disease
Published Tuesday, November 6, 2012 8:20AM EST
We often take vitamins thinking that they are good disease preventers -- but are they?
In a randomized study that included nearly 15,000 male physicians who were middle-aged or older, daily multivitamin use for more than 10 years of treatment and followup did not result in a reduction of major cardiovascular events, heart attack, stroke or death from cardiovascular disease, according to a study in JAMA.
As the authors point out, many adults take vitamin supplements to prevent chronic diseases or for general health and well-being. Studies also show that if you take a multivitamin, you may be less likely to engage in other preventive health behaviours. Although multivitamins are used to prevent vitamin and mineral deficiency, there is a perception that they may prevent cardiovascular disease.
This study done at Harvard, looked at data regarding multivitamin use and major cardiovascular events from the Physicians’ Health Study (PHS) II, a large-scale trial that tested the effects of long-term use of a common multivitamin on the risk of major cardiovascular events and cancer. The Physicians’ Health Study II is a randomized, placebo-controlled trial that began in 1997 with continued treatment and followup through June 1, 2011. A total of 14,641 male U.S. physicians initially 50 years of age or older (average, 64 years), including 754 men with a history of CVD at randomization, were enrolled.
This analysis measured major cardiovascular events, including nonfatal myocardial infarction (MI; heart attack), nonfatal stroke and death from CVD. Participants were randomized to multivitamin (n = 7,317) or placebo (n = 7,324).
During the midpoint of followup of 11.2 years, 1,732 men had major cardiovascular events, including 652 first heart attacks and 643 cases of stroke. As well, 829 men had cardiovascular death, with some men experiencing multiple events. A total of 2,757 (18.8 percent) men died during followup (multivitamin, n = 1,345; placebo, n = 1,412). In an analysis of the rate of events for men in each group, the researchers found that there was no significant effect of a daily multivitamin on major cardiovascular events, or total MI or total stroke. Taking a daily multivitamin was not significantly associated with a reduction in CVD mortality. There were fewer total deaths among multivitamin users, but this difference was not statistically significant.
The authors also found no significant effect of a daily multivitamin on rates of congestive heart failure, angina and coronary revascularization. Also, the effect of a daily multivitamin on total MI, total stroke and other cardiovascular end points did not differ between men with and without CVD at the beginning of the study.
This is the only large-scale, randomized, double-blind, placebo-controlled trial that has tested the long-term effects of a commonly available multivitamin in the prevention of chronic disease. According to the authors, and certainly seen by these event rates, the data does not support multivitamin use to prevent CVD, demonstrating the importance of long-term clinical trials of commonly used nutritional supplements. Whether a person should take a daily multivitamin requires consideration of an individual’s nutritional status. The aim of supplementation is to prevent vitamin and mineral deficiency, plus consideration of other potential effects, including a modest reduction in cancer which the authors will report on at a later date.
In an accompanying editorial from McMaster University and Hamilton General Hospital, it is pointed out that “robust data from multiple trials clearly confirm that CVD cannot be prevented or treated with vitamins.”
The editorial goes on to say that many people with heart disease risk factors or previous CVD events lead sedentary lifestyles, eat processed or fast foods, continue to smoke and stop taking lifesaving prescribed medications, but purchase and regularly use vitamins and other dietary supplements in the hope that this approach will prevent a future myocardial infarction or stroke. This distraction from effective CVD prevention is the main hazard of using vitamins and other unproven supplements. The message needs to remain simple and focused: CVD is largely preventable and this can be achieved by eating healthy foods, exercising regularly, avoiding tobacco products and, for those with high risk factor levels or previous CVD events, taking proven, safe and effective medications.