As a nutritional scientist, Jaakko Mursu had his doubts that vitamin supplements make people healthier.
But even Mursu, a researcher at the University of Minnesota, was surprised by the results of his latest study: that dietary supplements actually increased the risk of death for older women.
The study, published Monday, found that women who took multivitamins were 6 percent more likely to die than others. Vitamin B6 and iron supplements were associated with a 10 percent increase in death. Folic acid: 15 percent.
Only calcium appeared to lower the risk of death, according to the report published in Monday’s Archives of Internal Medicine.
“Any compound, even water, is harmful if the dose is high enough,” Mursu, the study’s lead researcher, said in an interview. Vitamins may be essential for the human body, he notes, but until now, there’s been little research on “the long-term consequences of these supplements.”
The results instantly prompted a backlash from supporters of the $27-billion-a-year supplement industry.
“These researchers would rather wait till we all get scurvy before acknowledging any need for supplemental nutrients,” said Duffy MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition.
The study, he said, “may make for interesting scientific water cooler discussion, but certainly does not warrant sweeping, overstated concerns for elderly women.”
Mursu, 38, said he was prepared for the backlash. “They don’t like our findings,” he said. “They honestly feel that they’re doing good.”
But the long-term research, he said, suggests otherwise. “We felt it was our obligation to speak up.”
Mursu and his team studied more than 38,000 women, aged 55 or older, who took part in the Iowa Women’s Health Study from 1986 to 2008.
The study found that the women who took supplements, in general, had healthier lifestyles than those who didn’t. They were less likely to smoke, have diabetes and be overweight, and more likely to eat fruits and vegetables and stay physically active. So the fact that the more health-conscious group had higher death rates was particularly surprising, Mursu said.
By 2004, 85 percent of the women in the study were taking nutritional supplements, the researchers found.
“If we look at the numbers … the effect is still not that dramatic,” Mursu said. “It doesn’t cut several years out of your life. It’s more likely months.”
Still, that goes beyond what previous studies have found, Mursu said.
In their report, the researchers concluded: “Although we cannot rule out benefits of supplements, such as improved quality of life, our study raises a concern regarding their long-term safety.”
A commentary piece, published alongside the study, suggested that consumers have been misled about the value of supplements.
“We think the paradigm ‘the more the better’ is wrong,” wrote Dr. Goran Bjelakovic and Dr. Christian Gluud, two European physicians. Too few vitamins may result in vitamin deficiency, they wrote, but too many may “increase the risk of toxic effects and disease.”
But MacKay, of the Council for Responsible Nutrition, said the study did not prove that supplements were dangerous. “It’s important to keep in mind that this is an associative — not a cause and effect — study,” he wrote in a prepared statement. He said that “reasonable use” of dietary supplements is just one part of a healthy lifestyle, and that “dietary supplements should not be expected, in and of themselves … to prevent chronic disease.”
Mursu agrees that the study doesn’t prove the supplements were to blame. But it does show that they don’t prevent heart disease or cancer or extend life, he said. “I would just advise people to put more into (an) improved diet.”