Multivitamins won’t help you live longer, major study finds
A major study released by the National Institute of Health on Wednesday found that multivitamins won’t prolong your life, despite one in three US adults taking them. This may come as a surprise, since the main motivation behind taking multivitamins is disease prevention and increasing the number of years you are healthy.
Academics looked at data from three large cohorts of studies in the US, all launched in the 1990s, and followed up with the 390,124 participants for up to 27 years. The adults did not have a history of cancer or other chronic diseases and the median age was 61.5 years. Out of this large survey, 54.6% were female and over 40% were never smokers.
Taking into account the 160,000 or so deaths that occurred during the follow-up, the researchers found that taking multivitamins was not associated with a mortality benefit, and that, instead, the risk of death was actually 4% higher among multivitamin users compared with non-users.
Supplementary vitamin intake could even be linked to detrimental health effects. In a commentary adjacent to the study, Dr Neal Barnard at the George Washington University School of Medicine & Health Sciences noted that beta carotene was found to increase chances of developing lung cancer; multivitamins containing vitamin K could make warfarin (a blood thinner) less effective; too much iron was associated with a higher likelihood of developing cardiovascular disease, diabetes and dementia; and calcium and zinc could clash with the absorption of some antibiotics.
Duane Mellor, a registered dietitian and senior lecturer at Aston Medical School, told The Guardian: ‘It’s not surprising to see these do not significantly reduce the risk of mortality.
‘A vitamin and mineral supplement will not fix an unhealthy diet on its own, but it can help cover key nutrients if someone struggles to get them from food. An example of this might be vitamin D, which adults in the UK are encouraged to take as a supplement in winter or vegans and vegetarians who might benefit from a supplement of vitamin B12.’
However, the study's authors said that: ‘We cannot preclude the possibility that daily multivitamin use may be associated with other health outcomes related to ageing.’
What were the study's drawbacks?
Criticising the research’s narrow focus in his commentary, Dr Barnard said: ‘Not captured in mortality data are potential benefits that do not affect longevity in cohorts of older adults. Supplementation with beta carotene, vitamins C and E, and zinc is associated with slowing the progression of age-related macular degeneration. In older individuals, multivitamin supplementation is associated with improved memory and slowed cognitive decline.
‘These findings make a case for obtaining vitamins from food sources, rather than supplements, to the extent possible,’ he added. ‘Micronutrients come most healthfully from food sources. When supplementation is required, it can often be limited to the micronutrients in question.’
Dr Jade A Cobern, MD, MPH, board-certified physician in paediatrics and general preventive medicine, told ABC News: ‘We can all likely benefit from adding more vegetables and whole grains or legumes into our diets,’ but ‘if a doctor prescribes a vitamin for someone, it's important to take that medication.’
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