Multivitamins and some dietary supplements, used regularly by an estimated 234 million U.S. adults, may do more harm than good, according to a study that tied their use to higher death rates among older women.
The use of multivitamins was associated with a 2.4 percent increased risk of death, according to the study published in the Archives of Internal Medicine. Calcium wasn’t associated with the danger and had a favorable effect on mortality, the authors found.
While people typically use supplements in the hope of maintaining or improving health, today’s study adds to evidence that some vitamins and supplements may be harmful, said Goran Bjelakovic, a doctor at the University of Nis in Serbia, and Cristian Gluud, a doctor at Copenhagen University Hospital in Denmark, in an accompanying editorial. The research also raises a concern that long-term use of supplements may not be safe, the researchers said.
“We see little justification for the general and widespread use of dietary supplements,” wrote the authors, led by Jaakko Mursu, a nutritionist at the University of Minnesota in Minneapolis and the University of Eastern Finland in Kuopio. It may be best to limit use of supplements to cases of deficiency, the authors wrote.
Almost 40,000 women, ages 55 through 69 when the study began, reported their supplement use at three points during the course of 19 years. The self-reported use of supplements increased over the years, jumping to 85 percent in 2004 from 63 percent in 1986.
The Risk of Iron
Other supplements linked with increased risk of death were vitamin B6, folic acid, iron, magnesium, zinc and copper. The finding that iron increased death risk by 3.9 percent was replicated in separate short-term analyses that lasted 4 years and 10 years.
About half of all U.S. adults reported using a dietary supplement in 2000, according to the study.
Dietary supplements don’t require the rigorous testing that drugs do. Vitamin sales at U.S. drugstores and other outlets, excluding Wal-Mart Stores Inc., were $3.3 billion last year, according to SymphonyIRI Group, a Chicago-based market research firm.
A 2007 study published in the Journal of the American Medical Association linked vitamin E, vitamin A and beta- carotene to higher death rates. Another, published in the same year in the Journal of the National Cancer Institute, linked multivitamins to an increase in prostate cancer.
“We cannot recommend the use of vitamin and mineral supplements as a preventive measure, at least not in a well nourished population,” Bjelakovic and Gluud wrote. “Those supplements do not replace or add to the benefits of eating fruits and vegetables and may cause unwanted health consequences.”
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