It's a decision that millions of Americans face every morning: to take, or not to take, that multivitamin. Now, a new study of almost 15,000 men over 50 suggests popping that daily supplement could cut cancer rates by 8 percent.
The study is good news for some Americans, who spend billions of dollars each year on the assumption that taking a daily multivitamin will help prevent disease.
"Despite the lack of definitive trial data regarding the benefits of multivitamins in the prevention of chronic disease, including cancer, many men and women take them for precisely this reason," said Dr. Michael Gaziano, professor of medicine at Harvard Medical School and lead author of the study published today in the Journal of the American Medical Association. "Our study shows a modest but significant benefit in cancer prevention."
It's unclear whether the results apply to women or men under 50.
Previous large studies, including a 180,000-patient study started in 1992 and the Women's Health Initiative study of 160,000 women published in 2009, found that multivitamins had little to no effect on the risk of cancer. In fact, a 2010 Swedish study of 35,000 women who reported using multivitamins had an increased risk of breast cancer. So what changed?
First, the new study randomly assigned men to two groups, one of which took a daily Centrum Silver® while the other took a placebo pill. Previous multivitamin studies have been observational, meaning that the participants weren't compared with someone taking a placebo.
Second, it followed the men, who were 65 years old on average, over 11 years – a longer follow-up than previous studies and sufficient time for cancer to develop.
And finally, the trial used a multivitamin, which is designed to fill nutritional gaps in a person's diet. Other trials have tested a single vitamin such as calcium or vitamin A, E or D in large doses, which is very different from how people normally get the vitamins and minerals they need from food.
"The reduction in total cancer risk in [the study] argues that the broader combination of low-dose vitamins and minerals contained in the [Centrum Silver®] multivitamin, rather than an emphasis on previously tested high-dose vitamins and mineral trials, may be paramount for cancer prevention," said Gaziano.
"Clearly the notion of megadoses of isolated nutrients has been proven wrong again and again," said Dr. David Katz, director of the Yale Prevention Research Center, who was not involved in the study. "Maybe the active ingredient in broccoli is broccoli."
So if a multivitamin prevents cancer because it provides a mix of nutrients similar to food, why not just eat more fruits and vegetables? Diets high in fruits and vegetables have been shown in observational studies to reduce the incidence of cancer and other chronic diseases. Sadly only 1.5 percent of the public gets the recommended daily allowance of fruits and vegetables, according to Katz.
Katz compared the results of this study to a prior study from Europe that showed people who never smoke, have a body mass index or BMI lower than 30, get regular exercise and adhere to a healthy diet, can reduce their risk of chronic disease by almost 80 percent.
"Clearly however, taking a multivitamin is easy; changing dietary patterns is hard," he said.
The Centrum Silver® used in the study was provided by the manufacturer Pfizer, but Pfizer did not fund the study.