For the second time in less than two months, researchers have published a meta-analysis of the existing research regarding vitamin and mineral supplements and cardiovascular disease.
The key finding of the new meta-analysis — published Tuesday in Circulation: Cardiovascular Quality and Outcomes, a journal of the American Heart Association (AHA) — is essentially the same as that of the earlier one: Taking multivitamin and mineral supplements does not prevent heart attacks or strokes. Nor does it reduce the risk of early death from those or other forms of cardiovascular disease (conditions affecting the heart and blood vessels).
The authors of the meta-analysis reached this conclusion after pooling and then analyzing data collected from 18 randomized controlled trials and cohort studies that investigated whether multivitamin and mineral supplements influenced cardiovascular outcomes. Collectively, these studies involved more than 2 million people and followed their participants for an average of 12 years. Eleven of the studies were from the United States. The rest were from France, Sweden, Germany and Japan.
“We meticulously evaluated the body of scientific evidence,” said Dr. Joonseok Kim, the study’s lead author and an assistant professor of cardiology at the University of Alabama at Birmingham, in a released statement. “We found no clinical benefit of multivitamin and mineral use to prevent heart attacks, strokes or cardiovascular death.”
The researchers did find an association between the use of multivitamin and mineral supplements and a lower incidence of coronary heart disease. But this “marginal benefit” appeared only in studies conducted outside the United States.
As Kim and his colleagues point out, users of supplements tend to eat more fruits and vegetables than non-users. That is especially true of supplement users living in Europe and Japan.
A diet rich in fruits and vegetables has been linked to a lower risk of cardiovascular disease. The lower incidence of coronary heart disease among users of multivitamin and mineral supplements in the European and Japanese studies may, therefore, have been due to their diet rather than to the supplements.
Getting the message across
The findings of the new meta-analysis support the current supplement recommendations of the United States Preventive Services Task Forces (USPSTF) and the American Heart Association. Neither group advises using these multivitamin and mineral supplements to prevent cardiovascular disease.
But Americans have been stubbornly slow in accepting that message. The use of multivitamin and mineral supplements is widespread in the United States, spurred on by the popular belief that such supplements help provide “insurance” against various chronic diseases, including cardiovascular disease.
Indeed, about a third of American adults take multivitamin and mineral supplements as a preventive measure. The annual cost of these and other dietary supplements comes to more than $32 billion a year.
Yet, as this meta-analysis shows, in the absence of a specific, diagnosed illness associated with a vitamin or mineral deficiency, the effect of supplements on health is neutral at best. And in some cases, the supplements may actually do harm. Research has linked vitamin E supplements to an increased risk of prostate cancer, for example.
“It has been exceptionally difficult to convince people, including nutritional researchers, to acknowledge that multivitamin and mineral supplements don’t prevent cardiovascular diseases,” said Kim. “I hope our study findings help decrease the hype around multivitamin and mineral supplements and encourage people to use proven methods to reduce their risk of cardiovascular diseases — such as eating more fruits and vegetables, exercising and avoiding tobacco.”
FMI: You can download and read the meta-analysis on the website for Circulation: Cardiovascular Quality and Outcomes. For information about proven actions you can take (during different decades of your life) to prevent cardiovascular disease, go to the American Heart Association’s website.