A new study suggests dietary supplements may be linked to a slightly increased risk of death in older women.
The 19-year study involved about 39,000 women with an average age of 62.
Those taking multivitamins or supplements of iron, Vitamin B-6, folic acid, magnesium, zinc and copper had, on average, a 2.4 percent increased chance of death over the course of the research.
Iron had the highest associated risk.
But one supplement -- calcium -- appeared to reduce the risk of death.
The study, appearing in the The Archives of Internal Medicine, didn't look at a possible direct cause-and-effect dynamic. It was an observational study based on self-reported supplement use and, its authors say, a range of factors aside from the use of supplements could have impacted the outcome.
"The headline," CBS News medical correspondent Dr. Jennifer Ashton cautioned, "like many, can be deceiving. This study was based on associated findings - it did not show a biologic cause-and-effect. (It was a) very large study done from 1986 to 2004 in Finland, very large study. They looked at almost 40,000 women, average age 62. That's important. They found in this group, 85 percent of them too took at least one dietary supplement a day, very similar to what we do here in this country. (The study) found an associated increased risk of desk among these older women for those in particular taking vitamin B-6, folic acid, iron, magnesium, zinc and copper. (The research) didn't say why, but did show that they had an increased risk of dying."
What is it about these supplements that causes the increased risk?
"In general," Ashton responded to "Early Show" co-anchor Chris Wragge, "we don't know. One well-respected doctor I work with said he's very skeptical about dietary supplements not because he thinks they don't work, but precisely because he thinks they do work. And in fact, we don't have enough data, we don't have enough well-constructed research to show us what the effect of these particular vitamins can do, especially when taken in high doses, excessive quantities.
"In particular, this study showed iron had an increased risk of death. And we know that, for certain people with certain types of blood disorders, excessive iron can be dangerous to the heart and liver."
"Early Show on Saturday Morning" co-anchor pointed out that many women take iron supplements, including those who are pregnant.
"Most women, most patients don't consider these supplements to be like medication," Ashton pointed out, "and in fact, they should."
Ashton offered tips for anyone taking supplements:
"Number one, if you are taking anything, especially when you've been taking it for (a long time), you want to discuss these with your doctor. You want to try to avoid self-diagnosis and falling into that trap of the marketing and advertising claims that a lot of these supplements portend. And also, do not assume that more is better. Really, do not take more than the recommended dosage, because we do know that these vitamins, like anything, can be dangerous."