Brains with more vitamin D function better, new research suggests.

The study, which scientists say is the first to examine levels of the vitamin in brain tissue, may help them further understand dementia and its causes.

It is estimated that some 55 million people in the world have dementia, and with this number expected to increase researchers are looking to better understand what causes the condition in order to develop treatments to slow or stop the disease.

Researchers at Tufts University in America looked at levels of vitamin D in adults who suffered from varying rates of cognitive decline.

This research reinforces the importance of studying how food and nutrients create resilience to protect the ageing brain against diseases such as Alzheimer’s disease and other related dementias

They found that people who had higher levels of vitamin D in their brains had better cognitive function.

Senior author Sarah Booth, director of the Jean Mayer USDA Human Nutrition Research Centre on Ageing (HNRCA) at Tufts, said: “This research reinforces the importance of studying how food and nutrients create resilience to protect the ageing brain against diseases such as Alzheimer’s disease and other related dementias.”

Vitamin D supports many functions in the body, including immune responses and maintaining healthy bones.

Fatty fish and fortified drinks such as milk or orange juice contain vitamin D, and brief exposure to sunlight also provides a dose of vitamin D.

However, the researchers warn people not to take large doses of the sunshine vitamin as a preventive measure.

The NHS recommends that during the autumn and winter, everyone (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10 micrograms of vitamin D.

Researchers examined samples of brain tissue from 209 people in the Rush Memory and Ageing Project, a long-term study of Alzheimer’s disease that began in 1997.

They assessed the cognitive function of the group, older people with no signs of cognitive impairment, as they aged, and analysed irregularities in their brain tissue after death.

The study looked for vitamin D in four regions of the brain—two associated with changes linked to Alzheimer’s disease, one associated with forms of dementia linked to blood flow, and one region without any known associations with cognitive decline related to Alzheimer’s disease or vascular disease.

They found that vitamin D was present in brain tissue, and high vitamin D levels in all four regions of the brain correlated with better cognitive function.

However, the levels of vitamin D in the brain did not associate with any of the physiological markers associated with Alzheimer’s disease in the brain studied.

These included amyloid plaque build-up, Lewy body disease, or evidence of chronic or microscopic strokes.

This means it is still unclear exactly how vitamin D might affect brain function.

Lead author Kyla Shea, a scientist on the Vitamin K Team and an associate professor at the Friedman School of Nutrition Science and Policy at Tufts, said: “We now know that vitamin D is present in reasonable amounts in human brains, and it seems to be correlated with less decline in cognitive function.

“But we need to do more research to identify the neuropathology that vitamin D is linked to in the brain before we start designing future interventions.”

The findings are published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.