Liz Szabo, USA TODAY
Dashing the hopes of those who hope to pop a pill to prevent heart disease, doctors announced Monday that daily multivitamins don't stave off cardiovascular problems, such as heart attacks, stroke or death.
The findings, published in The Journal of the American Medical Association and presented at the American Heart Association's Scientific Sessions in Los Angeles, come from the only large-scale, long-term trial of its kind, called the Physicians' Health Study II.
"Vitamin supplements will never be a substitute for a healthy diet," says co-study author JoAnn Manson, chief of preventive medicine at Boston's Brigham and Women's Hospital and a professor at Harvard Medical School. "While some people may need supplementation, it's not necessary for most of the population."
STORY: Multivitamins may lower cancer risk in men
The new study, which followed 14,661 male doctors for more than 11 years, had slightly more positive results for cancer. That part of the study, published last month, found that men who took multivitamins lowered their risk of cancer by 8%.
Vitamins are increasingly popular. About 39% of Americans took a multivitamin in 2003-2006, up from 30% in 1988-1994, according to an accompanying editorial. More than half of adults take at least one dietary supplement and 10% take more than five.
As an industry, dietary supplements have grown from $4 billion a year in 1994 to nearly $24 billion in 2008, according to the editorial. Because regulation of dietary supplements is less strict than for other drugs, makers of these pills are often able to make exaggerated claims about their benefits, with little to no evidence to back them up, writes the editorial's author, Eva Lonn, of McMaster University in Ontario, Canada.
Recent studies have largely failed to find much benefit from dietary supplements, however, whether taken as a single vitamin or multivitamin. High doses of vitamin E, vitamin C, betacarotene, selenium and B vitamins all failed to prevent cancer, according to carefully done studies. Studies of high-dose vitamin E have found that it actually increased the risk of stroke and prostate cancer.
Those results have frustrated and confused many consumers, partly because earlier studies suggested so many benefits for vitamins.
But studies like the one published today show the importance of conducting rigorous tests, in which patients are randomly assigned to one health intervention or another, with neither patients nor their doctors knowing which group they're in, says Christopher Cannon, also a Harvard professor of medicine and a cardiologist at Brigham and Women's Hospital.
These randomized, controlled trials - considered the gold standard of medical evidence - often disprove trends suggested by "observational" studies, in which researchers merely follow patients over time, says Cannon, who wasn't involved in the new study.
"We're not surprised by these results, but they don't discount the many other benefits that multivitamins provide, including filling nutrient gaps, helping prevent neural-tube birth defects, and serving in combination with other healthy habits as a basic and affordable insurance policy for overall wellness, " says Duffy MacKay, vice president for scientific affairs at the Council for Responsible Nutrition, an industry group.
McKay says the findings may not apply to everyone. That's because the doctors in the study were extremely healthy to begin with. So a modest improvement in health from vitamins might not be noticeable. "Unfortunately, this study population is not representative of your average American," McKay says.
Studies show that most people who take vitamins are leaner and more physically active than other people, McKay says.
Cardiologist Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York, says she hopes the study will remind people of the importance of the essentials, such as eating sensibly, exercising and avoiding tobacco, even if these changes are difficult for many Americans to make.
"Every single time, the most compelling prevention trials are in lifestyle management," says Steinbaum, who wasn't involved in the new study.
Steinbaum points to the well-known Lyon Heart Study, published in 1999, which found that heart attack survivors assigned to eat a Mediterranean diet reduced their risk of another heart attack or death by 70% in just two years. The Mediterranean diet includes lots of lean protein such as fish and beans, as well as whole grains, vegetables and healthier fats.
"We've never seen anything like that" from a pill, Steinbaum says, whether it's a statin or a supplement.