A major study has found that taking a daily multivitamin does not extend lifespan and may even increase the risk of early death.
Researchers in the US examined health records from nearly 400,000 adults without significant long-term illnesses to determine whether daily multivitamins could reduce their risk of death over the following two decades.
The study found that individuals who took daily multivitamins were slightly more likely to die during the study period compared to those who did not use multivitamins.
This led the government researchers to conclude that “multivitamin use to improve longevity is not supported.”
In the UK, nearly half of adults take multivitamins or dietary supplements weekly or more often, contributing to a domestic market valued at over half a billion pounds annually.
Globally, the market for these supplements is estimated to be worth tens of billions of dollars each year. In the US, a third of adults use multivitamins with the hope of disease prevention.
Despite their popularity, researchers have questioned the health benefits of multivitamins and warned that some supplements might be harmful.
For instance, while beta-carotene from natural food sources can protect against cancer, beta-carotene supplements have been linked to increased risks of lung cancer and heart disease, suggesting that these supplements lack crucial ingredients.
Additionally, iron, which is included in many multivitamins, can lead to iron overload and increase the risk of cardiovascular disease, diabetes, and dementia.
In this latest study, Dr. Erikka Loftfield and her team at the National Cancer Institute in Maryland analyzed data from three major US health studies.
These studies, which began in the 1990s, included information on participants’ daily multivitamin use and tracked 390,124 generally healthy adults for over 20 years.
The researchers found no evidence that daily multivitamins reduced the risk of death and actually observed a 4% higher mortality risk among users during the initial years of follow-up.
This increased risk may be due to the potential harms of multivitamins or the possibility that people start taking multivitamins when they are already seriously ill. These findings are detailed in Jama Network.
Dr. Neal Barnard, an adjunct professor of medicine at George Washington University and co-author of a commentary published with the study, acknowledged that vitamins can be beneficial in specific situations.
For instance, vitamin C historically prevented scurvy in sailors, and beta-carotene, vitamins C and E, and zinc have been shown to slow age-related macular degeneration, a condition that can cause severe vision loss.
However, vitamins may not necessarily reduce the risk of early death. A preliminary study in 2022 suggested that multivitamins might slow cognitive decline in old age, but further research is required.
Barnard stated, “multivitamins overpromise and underdeliver,” emphasizing that the evidence does not support their effectiveness in improving longevity.
He recommended focusing on a healthy diet, which provides 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, commented, “It’s not surprising to see these do not significantly reduce the risk of mortality.”
He added, “A vitamin and mineral supplement will not fix an unhealthy diet on its own, but it can help cover key nutrients if someone is struggling to get them from food.
For instance, vitamin D is recommended for adults in the UK during winter, and vegans and vegetarians might benefit from a vitamin B12 supplement.”
