Taking certain vitamin supplements may adversely affect people's lifespan, researchers have suggested.
Millions worldwide use antioxidant supplements such as vitamins A and E, and beta-carotene.
Looking at dozens of previous studies, Copenhagen University researchers suggested these appeared to raise, not lower, the risk of early death.
A supplements industry expert said the Journal of the American Medical Association study was fatally flawed.
But nutritionists said it reinforced the need to eat a balanced diet, rather than relying on supplements.
While vitamin supplements have been popular for decades, the precise benefits they offer - if any - remain uncertain, despite hundreds of research projects.
More recent theories suggest that certain vitamins consumed as part of a healthy diet - and perhaps taken in supplement form - may be able to prevent damage to the body's tissues called 'oxidative stress' by eliminating the molecules called 'free radicals' which are said to cause it.
This damage has been implicated in several major diseases including cancer and heart disease, yet the implication that vitamin supplements might protect people from these illnesses is controversial.
Source - BBC