In an opinion piece, the five authors say that for healthy people worried about chronic disease, there’s no clear benefit to taking vitamin and mineral pills. And in some instances, they may even cause harm.
The authors make an exception for supplemental vitamin D, which they say needs further research. Even so, widespread use of vitamin D pills “is not based on solid evidence that benefits outweigh harms,” the authors wrote. For other vitamins and supplements, “the case is closed”.
“The message is simple,” the editorial continued. “Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided.”
“We have so much information from so many studies,” Dr Cynthia Mulrow, senior deputy editor of Annals of Internal Medicine and an author of the editorial, said in an interview. “We don’t need a lot more evidence to put this to bed.”
Officials with the Natural Products Association, a trade organisation that represents supplement suppliers and retailers, said they were shocked by what they termed “an attack” on their industry, pointing to a study published last year that found a modest reduction in overall cancers in a long, randomised, controlled trial of 15,000 male doctors.
“Our members market and sell their products in order to assist people to achieve a healthier lifestyle,” said John Shaw, executive director of the association, adding that he could not understand why the industry was being criticised “for trying to promote health and wellness”.
The Cochrane Collaboration, which publishes reviews of medical evidence, has also concluded that taking vitamins does not extend life. An updated review of the evidence by the United States Preventive Services Task Force, published online on November 12, also concluded that there was limited evidence that vitamin and mineral supplementation could prevent cancer or cardiovascular disease.
The task force pointed out, however, that two clinical trials had found slight cancer reductions among men who took multivitamins. Yet other studies have found that beta-carotene supplements may actually increase the risk of lung cancer in smokers, the task force review noted, and that high doses of vitamins A and E cause harm and may increase the risk of death.
There have been few randomized clinical studies of the effects of multivitamins and minerals on heart disease, cancer and risk of death, said Dr Stephen P Fortmann, of the Kaiser Center of Health Research, who led the task force review. A draft of new task force recommendations, based on the updated review, said there was insufficient evidence to recommend taking or not taking vitamins.
Roni Caryn Rabin