Taking multivitamin and mineral supplements does not prevent heart attacks, strokes or cardiovascular death, according to a new analysis of 18 studies published in Circulation: Cardiovascular Quality and Outcomes, an American Heart Association journal.

"We meticulously evaluated the body of scientific evidence," said study lead author Joonseok Kim, M.D., assistant professor of cardiology in the Department of Medicine at the University of Alabama at Birmingham. "We found no clinical benefit of multivitamin and mineral use to prevent heart attacks, strokes or cardiovascular death."

The research team performed a "meta-analysis," putting together the results from 18 individual published studies, including randomized controlled trials and prospective cohort studies, totaling more than 2 million participants and having an average of 12 years of follow-up. They found no association between taking multivitamin and mineral supplements and a lower risk of death from cardiovascular diseases.

"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."

According to the United States Food and Drug Administration, unlike drugs, there are no provisions in the law for the agency to "approve" dietary supplements for safety or effectiveness before they reach the consumer, nor can the product's label make health claims to diagnose, cure, mitigate, treat or prevent a disease. As many as 30 percent of Americans use multivitamin and mineral supplements, with the global nutritional supplement industry expected to reach $278 billion by 2024.

Controversy about the effectiveness of multivitamin and mineral supplements to prevent cardiovascular diseases has been going on for years, despite numerous well-conducted research studies suggesting they don't help. The authors set out to combine the results from previously published scientific studies to help clarify the topic.

"Although multivitamin and mineral supplements taken in moderation rarely cause direct harm, we urge people to protect their heart health by understanding their individual risk for heart disease and stroke and working with a healthcare provider to create a plan that uses proven measures to reduce risk. These include a heart-healthy diet, exercise, tobacco cessation, controlling blood pressure and unhealthy cholesterol levels, and when needed, medical treatment," Kim said.

The American Heart Association does not recommend using multivitamin or mineral supplements to prevent cardiovascular diseases.

"Eat a healthy diet for a healthy heart and a long, healthy life," said Eduardo Sanchez, M.D., the American Heart Association's chief medical officer for prevention and chief of the Association's Centers for Health Metrics and Evaluation, who was not a part of this study. "There's just no substitute for a balanced, nutritious diet with more fruits and vegetables that limits excess calories, saturated fat, trans fat, sodium, sugar and dietary cholesterol."