Vitamin D deficiency linked to dementia
7 August 2014 Last updated at 07:53 BST
Scientists in the United States say they have found the strongest evidence yet that older people who do not develop enough vitamin D by getting out in the sunshine may be more likely to develop dementia.
In a study published in the journal Neurology, the researchers say it is the biggest study of its kind and the association was much stronger than they had expected.
But they emphasised this does not prove there is a link, or that taking vitamin D supplements could delay or prevent dementia.
Adam Brimelow reports.