Oct. 10, 2011 -- For the nutrient conscious, a daily caplet of vitamins and minerals might seem like a sure way to get all the necessary nutrients you could miss in your diet. But a new study reports that those supplements may not be helpful, and in some cases, could even be harmful for older women.
The study looked at more than 38,000 women age 55 and older who participated in the Iowa Women's Health Study since the mid-1980s. The researchers found that when it came to reducing the risk of death, most supplements had no effect on women's health.
In fact, women who took certain kinds of dietary supplements -- vitamin B6, folic acid, magnesium, zinc, copper, iron and multivitamins -- faced a slightly higher risk of death than women who did not. Only women who took supplemental calcium showed any reduction in their risk of death.
The study was published today in the Archives of Internal Medicine.
Jaakko Mursu, the study's lead author, said the findings add to a growing collection of research showing that people who take dietary supplements are getting few health benefits in return.
"I would conclude that supplements are not protective against chronic diseases," Mursu said. "In some cases they may be harmful, especially if used for a long time."
News about the benefits and risks of dietary supplements seems to change by the week. Buzz about potential health boosts from antioxidants like beta carotene and vitamin E was squelched by recent studies showing that these supplements can actually be harmful. Some studies, like the current one, have touted the benefits of added calcium while others have shown that it carries potential health risks.
Dr. Donald Hensrud, chair of preventive medicine at the Mayo Clinic, said the conflicting evidence seems overwhelming, but the new study helps to clarify the overall message.
"It can be confusing for the public when something isn't entirely black and white," Hensrud said. "But based on this new study, people should be even a little more cautious now about taking these supplements."
Experts noted that supplements are beneficial for people who have some kind of nutritional deficiency, like anemia or osteoporosis. But many people who take dietary supplements are healthy and just want to be healthier.
In 2003, the National Institutes of Health (NIH) found that roughly half of Americans reported taking at least one dietary supplement, creating nearly $20 billion in annual industry profits. And dietary supplement use becomes more common as people get older. In the current study, the numbers of women who reported taking supplements increased over time -- from 63 percent in 1986, to 75 percent in 1997 and 85 percent in 2004.
The authors noted that their data can't distinguish whether the women they studied were taking supplements to fight diseases or simply to maintain health.
"People take nutritional supplements for a variety of reasons, both related directly to a health problem or only related to a health belief that a little of something is good and a lot of something must be better. This is not always the case," said Dr. Charles Clark, a professor of medicine at the Indiana University School of Medicine.
Experts say the best way to ensure that you're getting all the nutrients you need is still to eat a well-balanced diet.
Connie Diekman, director of nutrition at Washington University in St. Louis, said women who want to take additional vitamins and minerals should consult with their doctors to make sure those supplements are safe and actually necessary.
"Supplements should be viewed as ways to boost intake when food does not meet need," she said.