Taking daily vitamin D lowers the chances of developing dementia, especially in women, a study suggests.
Those who took supplements lived free from the disease for longer with 40 per cent fewer cases overall, researchers found.
Experts believe the vitamin may help to reduce the build up of amyloid plaques and tau, the accumulation of which is linked to Alzheimer’s disease and dementia.
Scientists from Exeter University and Calgary’s Hotchkiss Brain Institute in Canada analysed a group of 12,388 people in the US National Alzheimer’s Coordinating Centre.
Taking vitamin D could reduce the build up of amyloid plaques and tau, which are linked to Alzheimer’s disease, according experts
About 4,600 – 37 per cent – of the participants who had an average age of 71 and were dementia-free at the start of the trial – took supplements.
Some 2,696 people went on to be diagnosed with dementia over the next 10 years.
Of them, around three-quarters (2,017) never took supplements during that period while a quarter did (679).
There were 40 per cent fewer cases of the disease among those who reported taking vitamin D supplements, according to the findings published in Alzheimer’s & Dementia.
WHAT SHOULD A BALANCED DIET LOOK LIKE?
Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain, according to the NHS
• Eat at least 5 portions of a variety of fruit and vegetables every day. All fresh, frozen, dried and canned fruit and vegetables count
• Base meals on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain
• 30 grams of fibre a day: This is the same as eating all of the following: 5 portions of fruit and vegetables, 2 whole-wheat cereal biscuits, 2 thick slices of wholemeal bread and large baked potato with the skin on
• Have some dairy or dairy alternatives (such as soya drinks) choosing lower fat and lower sugar options
• Eat some beans, pulses, fish, eggs, meat and other proteins (including 2 portions of fish every week, one of which should be oily)
• Choose unsaturated oils and spreads and consuming in small amounts
• Drink 6-8 cups/glasses of water a day
• Adults should have less than 6g of salt and 20g of saturated fat for women or 30g for men a day
Source: NHS Eatwell Guide
Professor Zahinoor Ismail, of the University of Calgary and the University of Exeter, who led the research, said: ‘We know that vitamin D has some effects in the brain that could have implications for reducing dementia, however so far, research has yielded conflicting results.
‘Our findings give key insights into groups who might be specifically targeted for vitamin D supplementation.
‘Overall, we found evidence to suggest that earlier supplementation might be particularly beneficial, before the onset of cognitive decline.’
Vitamin D comes from foods – such as oily fish, supplements and exposing skin to sunlight.
Older people’s skin can be less efficient at converting sunlight into Vitamin D, making them more likely to be deficient and reliant on other sources.
While benefits from supplements were seen among both sexes, the effects were greatest among women and in people with normal cognition, compared to those who reported signs of mild cognitive impairment – changes to cognition which have been linked to a higher risk of dementia.
Experts believe the greater effects among women could be because levels of oestrogen, which is linked to the activation of vitamin D, fall during menopause.
This could lead to greater effects from taking the vitamin, which is often recommended to women because of links to other health benefits, such as bone health.
The effects of vitamin D were also significantly greater in people who did not carry the APOEe4 gene, known to present a higher risk for Alzheimer’s dementia, compared to non-carriers.
The authors suggest that people who carry the APOEe4 gene absorb vitamin D better from their intestine, which might reduce the vitamin D supplementation effect. However, no blood levels were drawn to test this hypothesis.
Previous research has found that low levels of vitamin D are linked to higher dementia risk.
Vitamin D is involved in the clearance of amyloid in the brain, the accumulation of which is one of the hallmarks of Alzheimer’s disease.
Studies have also found that vitamin D may provide help to protect the brain against build-up of tau, another protein involved in the development of dementia.
Dr Rosa Sancho, head of research at Alzheimer’s Research UK, said: ‘Its findings hint that the onset of dementia happens later among people with a history of taking common vitamin D supplements, and that the effect appears stronger among people without genetic risk factors or existing memory and thinking difficulties.
‘But there is more work to do to properly understand this link – the study didn’t collect data on participants’ lifestyle and health history in the years before the research began. This is an important omission.
‘Extensive research shows that habits and behaviours in midlife, such as keeping a healthy heart or not smoking, can reduce our dementia risk in later life. In their research paper, the researchers speculate as to how the vitamin D could be linked to dementia risk, but these claims need additional research to confirm.’