Older people who don't have enough Vitamin D in their system could be at double the risk of developing dementia.
A new study out of England finds people who had low levels of Vitamin D were much more likely to have dementia or Alzheimer's.
Researchers caution the study doesn't prove that low levels of Vitamin D causes dementia.
But they say the findings should send a warning signal to people who don't have enough Vitamin D.
"Clinical trials are now needed to establish whether eating foods such as oily fish or taking vitamin D supplements can delay or even prevent the onset of Alzheimer's disease and dementia," said lead author David Llewellyn, with the University of Exeter Medical School.
The study was published in the August issue of Neurology.