People who intake of vitamins or supplements are at higher risk of dying early than those not taking them, reveals a new study.
In the new study, researchers gathered data on nearly 1,800 people between the ages of 62 and 74 who were participating in a prospective, population health study of the residents of one town in Finland.
Over a 10-year period, 59 of the 221 people (26.6 percent) taking a vitamin or supplement died, whereas 281 of the 1,553 people (18.1 percent) of the nonusers died.
The findings are in line with a recent study from University of Minnesota researchers, who looked at 38,000 women who were around age 62 at the study's start, and found a slight increase in mortality among those taking vitamins or supplements.
They found, for example, that 40.8 percent of 13,000 women taking a daily multivitamin died over the 19-year study, whereas 39.8 percent of the 10,000 women who hadn't taken a daily multivitamin had died.
Both studies showed an association, not a cause-and-effect link.
The Minnesota study had prompted ideas that supplement users were a "self -selected" group, Tuomainen told MyHealthNewsDaily.
It could be that people who take supplements tend to have more health problems than nonusers to start with, or are more likely than nonusers to have close relatives with health problems (which could mean they are at greater risk for developing later problems themselves).
But the new study suggests that those hypotheses may not explain the increased death risk, Tuomainen said.
He and his co-authors adjusted their analysis to account for people who reported pre-existing diseases and a family history of the "major killer" diseases, he said.
The adjustment brought down the increased risk of dying seen among the supplement users, but did not make it disappear, he said.
Part of the reason behind the link may be that taking vitamins or supplements that include more iron or copper than the body needs are harmful for health, Tuomainen added.
These metals are pro-oxidants, and may trigger the type of stress in the body (oxidative stress) that is associated with chronic diseases, though more work is needed to show this.
The findings have been published in the journal Archives of Internal Medicine.