Over 60s should take vitamin D supplements to ward off cognitive decline and dementia, scientists have advised, after a study showed those with deficiencies suffered rapid mental deterioration.
Known as the sunshine vitamin because the body produces it when in contact with sunlight, vitamin D is essential for promoting calcium absorption and bone health and some studies suggest it may protect against cancer, diabetes and multiple sclerosis.
But new research suggests it also plays an important role in mental health in later life.
Scientists at the University of California and Rutgers University in the US found that over-60s with vitamin D deficiency declined mentally at a rate three times faster than those with adequate levels.
The researchers suggest that low vitamin D levels should now be considered a risk factor for dementia, particularly among people with darker skin tones.
“On average, people with low vitamin D declined two to three times as fast as those with adequate vitamin D,” said Professor Joshua Miller, of the Department of Nutritional Sciences at Rutgers University.
“This work, and that of others, suggests that there is enough evidence to recommend that people in their 60s and older discuss taking a daily vitamin D supplement with their physicians.
“Even if doing so proves to not be effective, there’s still very low health risk to doing it,” he said.
A recent survey suggested that around 50 per cent of all adults have some degree of vitamin d deficiency, which has been blamed on too much time spent indoors and increased use of sunblock.
Although vitamin D is found in foods like oily fish, most people cannot get enough of the vitamin through diet alone, and those living in higher latitudes are at greater risk.
“Some people may have had melanoma or fear getting it,” added Prof Miller. “Or, they may live in climates where the sun isn’t powerful enough, or do work that keeps them out of the sun. That’s where supplements come in.”
The study looked at 400 people with a mean age of 76, who were either cognitively normal, had mild cognitive impairment or were suffering from dementia.
Over five years of follow-up, vitamin D deficient individuals experienced cognitive declines that were two-to-three times faster than those with adequate serum vitamin D levels. In other words it took only two years for the deficient individuals to decline as much as their counterparts with adequate Vitamin D declined during five years.
“We expected to see declines in individuals with low vitamin D status,” said Professor Charles DeCarli, director of the Alzheimer’s Disease Center at the University of California.
“What was unexpected was how profoundly and rapidly low vitamin D impacts cognition.
“I don’t know if replacement therapy would affect these cognitive trajectories. That needs to be researched and we are planning on doing that.
“This is a vitamin deficiency that could easily be treated and that has other health consequences. We need to start talking about it. And we need to start talking about it, particularly for people of colour, for whom vitamin D deficiency appears to present an even greater risk.”
Dementia experts in Britain said more studies needed to be carried out to see if vitamin D really could protect against dementia, and in the meantime, people should stick to a healthy diet and exercise.
Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, said: “Vitamin D plays an important role in keeping our bodies healthy and there are a number of studies that suggest a link between vitamin D deficiency and memory and thinking difficulties.
“While this new research suggests an association between low vitamin D levels and faster rates of memory loss, we don’t yet know whether taking supplements could stave off dementia or slow down decline in those who are already living with the condition.
“A balanced diet is important for brain health and, alongside physical activity and keeping weight and blood pressure in check, can help reduce dementia risk.”
Dr Doug Brown, Director of Research at Alzheimer’s Society, added: “Shedding light on how we can reduce the risk of getting dementia is one of the most important tasks facing today’s health researchers. While this study found that people with low levels of vitamin D experience faster mental decline, we await the results of large-scale clinical trials to confirm whether there is a direct link between vitamin D and memory problems. Although people with dementia and mild cognitive impairment were included in this study, there was no indication that vitamin D helps prevent development of dementia.
“During the warm weather, spending just 15 minutes in the sunshine is enough to boost your vitamin D levels. However, there remains insufficient evidence that sunlight or vitamin D supplements will reduce your risk of dementia. Eating a balanced diet and exercising regularly is the best way to help keep your brain healthy.”
The research was published in the online journal JAMA Neurology.