Iron tablets taken by millions of people could damage the body within just 10 minutes, a study has warned.
Tests showed the mineral rapidly causes DNA damage in blood vessels.
While they were carried out in a lab setting, rather than living people, researchers found the levels of iron given in supplements may be too high and harmful.
Iron supplements may contain 10 times more than is necessary for health, the researchers said.
In future, doctors may want to think carefully about prescribing the minimum dose of iron necessary to patients who need it, researchers said.
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