Vitamin D and calcium supplements taken together in low doses offered no protection against dementia, according to a US study of older women but scientists are still holding hope for vitamin D alone. Past research has suggested vitamin D might protect against memory loss and overall functional decline in the aging brain  but more than 2,000 women, who took part in the study and had taken 400 units of vitamin D and 1,000 mg of calcium daily for eight years developed impairments at the same rates as a comparison group.

But researchers  said during these years they gained a better understanding of how calcium and vitamin D might have conflicting effects  so the combination of the two might explain the disappointing results.

“I think the definitive study will just look at the effects of vitamin D,” said Rebecca Rossom  from Health Partners Institute for Education and Research.
She added the study is still important because it “gets closer to how women take vitamin D” to build bone density.