There is also some evidence that vitamin D can dampen down an over-active immune system.
Alternatively, it may boost levels of antioxidants that in effect detoxify the brain.
The researchers stressed that many people, particularly in older age, were vitamin D deficient.
Therefore, if it were possible to stave off the effects on ageing on the brain with vitamin D supplements the implications for the health of the population could be significant.
Professor Tim Spector, of King's College London, has carried out research into the effect of vitamin D on ageing.
He said: "This is further evidence from observational studies that vitamin D is likely to be beneficial to reduce many age-related diseases.
"Taken together with similar data that shows its importance in reducing arthritis, osteoporotic fractures, as well as heart disease and some cancers, this underscores the importance of vitamin D for humans and why evolution gave us a liking for the sun.
"We also know that our genes also determine our vitamin D levels which explains why individuals can vary so much.
"We now need to study the best way to give using vitamin D properly in prevention."
Dr Iain Lang, of the Peninsula Medical School in Exeter, carried out the earlier research.
He agreed there was mounting evidence suggesting vitamin D was good for the brain, but warned that it was possible that poor mental performance could be down to an inadequate diet, of which vitamin D deficiency might be just one manifestation.