Multivitamins are cheap, convenient, and provide a little bit of reassurance if our diet isn’t quite as healthy as we’d like. But a recent study of nearly 400,000 people spanning 20 years found they didn’t help users live longer, and in fact appeared to show a 4% increased mortality risk. Ian Sample hears from JoAnn Manson, a professor of medicine at Harvard Medical School, to find out what the evidence tells us about the overall health benefits of multivitamins, and how consumers can navigate this large and sometimes confusing market. Help support our independent journalism at theguardian.com/sciencepod