Men who take a multivitamin each day are no less likely to develop heart disease than men who don't, a new study shows.
The research follows an October study that found men taking a multivitamin each day were slightly less likely to develop cancer. Meanwhile, two other new studies released at the same medical conference found fish oil didn't help for an irregular heartbeat condition called atrial fibrillation, even though it is thought to help certain people with heart disease or high levels of fats called triglycerides in their blood.
The bottom line on dietary supplements? Vitamins have varied effects and whether one is right for you may depend on your personal health profile, diet and lifestyle, the studies suggest.
"Multivitamins are the most common supplement taken by at least one-third of all U.S. adults," study author Dr. Howard D. Sesso, an associate professor of medicine at Brigham & Women's Hospital in Boston, Mass., said in a written statement. "While multivitamins are typically used to prevent vitamin and mineral deficiency, there is an unproven belief that they may have benefits on other chronic diseases, including heart attack, stroke or cardiovascular death."
The studies were presented Monday at an American Heart Association conference in Los Angeles and the vitamin research and one fish oil study were published in the Journal of the American Medical Association.
No government agency recommends routine multivitamin use for preventing chronic diseases, and few studies have tested them to see if they can. A leading preventive medicine task force even recommends against beta-carotene supplements, alone or with other vitamins, to prevent cancer or heart disease because some studies have found them harmful. And vitamin K can affect bleeding and interfere with some commonly used heart drugs.
Sesso's study looked at nearly 15,000 healthy male doctors given monthly packets of Centrum Silver or fake multivitamins. After about 11 years, there were no differences between the groups in heart attacks, strokes, chest pain, heart failure or heart-related deaths.
Side effects were fairly similar except for more rashes among vitamin users. The National Institutes of Health paid for most of the study. Pfizer Inc. supplied the pills and other companies supplied the packaging.
"It's also important to note that taking a daily multivitamin appears to be safe, with no harm found," study co-author Dr. J. Michael Gaziano, chief of the Division of Aging at Brigham and Women's Hospital, said in a written statement. "In addition, it's also important to consider other potential effects of long-term multivitamin use, including a modest reduction in total cancer recently reported in our trial."
Multivitamins also may have different results in women or people less healthy than those in new study - only 4 percent smoked, for example.
The fish oil studies tested prescription-strength omega-3 capsules from several companies in two different groups of people for preventing atrial fibrillation, a fluttering, irregular heartbeat.
One from South America aimed to prevent recurrent episodes in 600 participants who already had the condition. The other sought to prevent it from developing in 1,500 people from the U.S., Italy and Argentina having various types of heart surgery, such as valve replacement. About one third of heart surgery patients develop atrial fibrillation as a complication.
Both studies found fish oil ineffective.
The National Institutes of Health's Office of Dietary Supplements has more information on multivitamins.