New research has linked levels of vitamin D in midlife with toxic tangles of tau protein that accumulate in the brains of those with Alzheimer’s disease.

A statistical analysis of blood samples and brain scans from 793 adults showed that the more vitamin D in someone’s system in middle age, the lower the amount of tau protein tangles they tended to have years later.

The finding comes from an international team of researchers, and while it doesn’t prove direct cause and effect, it suggests an association that’s worth looking at.