Taking a daily multivitamin does not help people live longer and may even increase the risk of premature death, a large-scale study has found.
Researchers in the US analyzed the health records of nearly 400,000 adults without serious long-term illnesses to see whether daily multivitamins reduced their risk of death over the next twenty years.
Rather than living longer, people who consumed daily multivitamins were slightly more likely than non-users to die during the study period, prompting government researchers to say that “the use of multivitamins to improve longevity is not supported” .
Almost half of British adults use this multivitamins or nutritional supplements once a week or more, part of a domestic market worth more than half a billion pounds annually. The global market for the supplements is estimated at tens of billions of dollars per year. In the US, a third of adults take multivitamins in hopes of preventing disease.
But despite the popularity of multivitamins, researchers have questioned their health benefits and even warned that the supplements may be harmful. For example, while natural food sources of beta-carotene protect against cancer, beta-carotene supplements may increase the risk of lung cancer and heart disease, suggesting that the supplements are missing key ingredients. Meanwhile, iron, which is added to many multivitamins, can lead to diabetes iron overload and increase the risk of cardiovascular disease, diabetes and dementia.
For the latest work, Dr Erikka Loftfield and colleagues from the National Cancer Institute in Maryland analyzed data from three large US health studies. All launched in the 1990s and collected details of participants’ daily multivitamin use. The data involved 390,124 generally healthy adults who were followed for more than 20 years.
The researchers found no evidence that daily multivitamins reduced the risk of death and instead reported a 4% higher mortality risk among users in the first years of follow-up. The increased risk of death may reflect the harm multivitamins can cause or a trend for people to start taking daily multivitamins when they develop serious illness. Details will be published in Jama Network.
Dr. Neal Barnard, adjunct professor of medicine at George Washington University and co-author of a commentary published alongside the study, said vitamins were helpful in specific cases. Historically, vitamin C saved sailors from scurvy, while beta-carotene, vitamins C and E and zinc appear to slow age-related macular degeneration, a condition that can lead to severe vision loss.
It is also true that vitamins can be helpful without reducing the risk of premature death. A preliminary 2022 study found evidence that multivitamins might slow cognitive decline in old age, but more research was needed.
But “multivitamins over-promise and under-deliver,” Barnard said. “The main point is that the multivitamins don’t help. The science is not there.” Instead of taking multivitamins, we should eat healthy foods, he said, that provide a wide range of micronutrients, macronutrients and fiber, while limiting saturated fat and cholesterol.
Duane Mellor, a registered dietitian and senior lecturer at Aston Medical School, said: “It is not surprising to see that these do not significantly reduce the risk of mortality.
“A vitamin and mineral supplement will not on its own solve an unhealthy diet, but it can help cover important nutrients if someone has trouble getting them from food. An example of this could be vitamin D, which adults in the UK are encouraged to take as a supplement in winter, or vegans and vegetarians who could benefit from a vitamin B12 supplement.”