An analysis of 400,000 healthy adults found that taking a daily multivitamin offers no health benefits and may increase the risk of death.
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Ian Sample/The Guardian
Taking a daily multivitamin doesn’t extend your life and may actually increase the risk of premature death, a large study has found.
US researchers analysed the health records of almost 400,000 adults without any long-term serious illnesses to see whether taking a daily multivitamin reduces the risk of death over the next 20 years.
Far from living longer, people who took daily multivitamins were slightly more likely to die during the study period than non-takers, leading government researchers to comment that “the use of multivitamins to extend life span is not supported.”
Photo: Ou Su Mei, Taipei Times
The global market for supplements is estimated to be worth tens of billions of dollars each year. In the United States, one-third of adults take a multivitamin in the hope of preventing disease.
But despite the popularity of multivitamins, researchers have questioned their health benefits and even warned that supplements may be harmful. For example, natural food sources of beta-carotene protect against cancer, but beta-carotene supplements may increase the risk of lung cancer and heart disease, suggesting that supplements are missing a key ingredient. Meanwhile, the added iron in many multivitamins may cause iron overload, increasing the risk of cardiovascular disease, diabetes, and dementia.
In the latest study, Ericka Loftfield of the National Cancer Institute in Maryland and her colleagues analysed data from three major US health studies, all launched in the 1990s, that collected details about participants’ daily multivitamin intake, covering 390,124 generally healthy adults who were followed for more than 20 years.
The researchers found no evidence that taking a daily multivitamin reduced the risk of death, but rather reported a 4 percent higher risk of death among multivitamin users in the first few years of follow-up. The increased risk of death could reflect harm caused by multivitamins or a tendency for people to start taking a daily multivitamin when they develop a serious illness. More details are published in Jama Network.
Neal Barnard, an adjunct professor of medicine at George Washington University and co-author of a commentary published along with the study, said vitamins can be helpful in certain cases: Historically, sailors were saved from scurvy by vitamin C, while beta-carotene, vitamins C and E, and zinc appear to slow the progression of age-related macular degeneration, which can lead to severe vision loss.
It’s also possible that vitamins may be beneficial without reducing the risk of early death. A preliminary 2022 study found evidence that multivitamins may slow cognitive decline in old age, but more research was needed.
But “multivitamins are over-promising and under-delivering,” says Bernard, “The bottom line is that they don’t work. The science isn’t there.”
Instead of taking a multivitamin, people should eat healthy foods that provide a wide range of micronutrients, macronutrients and dietary fiber while limiting saturated fat and cholesterol, he said.
“It’s not surprising that these don’t significantly reduce the risk of death,” said Duane Mellor, a registered dietitian and senior lecturer at Aston Medical School.
“Vitamin and mineral supplements cannot alone change an unhealthy diet, but can help to make up for key nutrients when it is difficult to get them from food. Examples of this include vitamin D, which is recommended for adults to take as a supplement in the winter in the UK, and vegans and vegetarians who may benefit from vitamin B12 supplements.”
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