Taking a multivitamin every day doesn't seem to ward off thinking and memory problems. Nor will it prevent worsening heart disease or death among people who have already had a heart attack.
Those findings come from two reports published Monday in the Annals of Internal Medicine. The studies represent the latest in a growing body of evidence suggesting the popular supplements probably aren't doing most users a lot of good.
"People over time and particularly people in the United States have been led to believe that vitamin and mineral supplements will make them healthier, and they're looking for a magic pill," Dr. Cynthia Mulrow says.
But such a pill doesn't exist, said Mulrow, a senior deputy editor at the journal who co-wrote an editorial published with the new research.
"People ... should be active, should not (overeat), should avoid excessive alcohol and should not be spending money on these pills, these vitamins and minerals," she told Reuters Health.
The studies follow a review of earlier research published online last month. It found multivitamins had no effect on heart disease and possibly a small effect on cancer risk, but only among men.
To look at whether vitamins affect thinking and memory skills, researchers randomly assigned about 6,000 older male doctors to take either a standard multivitamin or vitamin-free placebo as part of a larger men's health study. Then they gave the men up to four memory tests over the next 12 years.
Howard Sesso from Brigham and Women's Hospital in Boston and his colleagues found no cognitive differences between the vitamin and placebo groups at any time point. Nor did scores on the memory tests drop any faster among men in one group versus the other.
The second new study included both men and women who'd had a heart attack. About 1,700 of them were randomly assigned to take supplements — this time high doses of vitamins and minerals — or placebo pills.
Over an average of four and a half years, 27 percent of people taking vitamins died or had another heart attack or other cardiovascular problem. That compared to 30 percent of participants taking placebos — a difference that could have been due to chance.
People in that study had to take six vitamin pills a day and many weren't so good about sticking to that regimen, researchers led by Dr. Gervasio Lamas of the Mount Sinai Medical Center in Florida wrote. That could have influenced the results.
"As of now, there is no need to be taking multivitamins and multiminerals to prevent heart disease, and there is extensive evidence on that," Lamas told Reuters Health.
"For the general population who [is healthy] and they are taking vitamins because they are thinking that somehow the vitamins are going to make them do better, people are entitled to waste their money in any way that they like," he says.
Americans spent $28 billion on supplements in 2010, Mulrow and her colleagues noted.
Neither study found side effects tied to multivitamin use. So people probably aren't hurting themselves by taking multivitamins, especially in standard doses, researchers add.
Sesso says because of the possible cancer-related benefits tied to multivitamins, they are still worth considering — in particular for people who may not get enough vitamins in their diet.
A prior study by his team found an 8 percent lower risk of cancer among men assigned to take multivitamins, as well as a lower risk of cataracts.
"We really need to manage our expectations about why we're taking multivitamins," says Duffy MacKay, vice president of scientific and regulatory affairs at the Council for Responsible Nutrition (CRN).
CRN is a Washington, D.C.-based trade group that represents dietary supplement manufacturers and ingredient suppliers.
He says the main reasons people report talking multivitamins are for overall health and wellness and to fill nutrient gaps.
Research shows Americans often don't get all recommended nutrients from their diets, and that a multivitamin helps fill those gaps, MacKay told Reuters Health.
"That's reason alone that a multivitamin should be consumed," he says.
"It's ultimately an individual decision," Sesso told Reuters Health.
Considering how many people take multivitamins — up to half of all U.S. adults — he said there's still a need for more research on their effects.
Mulrow had a different perspective. Based on the research that has been done and the lack of general benefit, she questioned whether any more money should be spent on studying vitamin supplements.
"We think we shouldn't be doing a lot more studies on most of these," she says.