Americans spend tens of billions on vitamin and mineral supplements each year. But new studies reveal that taking multi-vitamins may be of little benefit to the millions who consume them.
A team of researchers found no clear benefit from taking vitamin and mineral pills.
The findings of two studies, published in the Annals of Internal Medicine journal, reveal that most supplements do not prevent chronic disease or death. According to the studies, their use is not justified and should be avoided.
The first study, released online Nov. 12 in Annals, was a review of 24 studies and two trials of more than 350,000 individuals that looked at the role of vitamin supplements in curbing chronic disease. Researchers sought evidence to update the vitamin treatment guidelines for the U.S. Preventive Services Task Force, a panel of medical experts who recommend the government's guidelines for treatments.
That review found no evidence that vitamin and mineral supplements would reduce heart disease for the people who take them. Two of the trials found a small, "borderline-significant benefit" in cancer risk reduction, but only in men. Overall, the panel concluded there was no solid evidence for or against taking vitamins and minerals individually nor does a multivitamin prevent heart disease or cancer. More strikingly, researchers found enough evidence to recommend not taking beta-carotene or Vitamin E for preventing either disease, finding they not only didn't help but the former may raise the risk for lung cancer in at-risk individuals.
In the absence of clear evidence about the benefit of most vitamins and multivitamins on cardiovascular disease and cancer, health care professionals should counsel their patients to eat a healthful, well-balanced diet rich in nutrients, the Task Force concluded.
The next study, published Dec. 16 in Annals, looked at cognitive health to assess whether long-term use of multivitamins would have any effect. Researchers assigned 5,950 male doctors aged 65 and older to take either a daily multivitamin or placebo for 12 years in a random, placebo-controlled trial.
Based on results of memory tests, the researchers found the multivitamin did nothing to slow cognitive decline among men 65 and older compared to placebo takers.
The reports suggest that some supplements such as beta-carotene and Vitamin E may even be harmful.
Researchers made an exception for Vitamin D, saying more research is needed.