March 22, 2023
Older people who took vitamin D supplements were less likely to develop dementia, according to a new report. The brain benefits of vitamin D appeared to be particularly pronounced in older women, though older men also saw a reduced dementia risk. The findings add to growing evidence that maintaining adequate levels of vitamin D may play a role in helping to ward off Alzheimer’s disease, the most common form of dementia.
For the study, researchers at the University of Calgary in Canada and the University of Exeter in Britain looked at 12,388 older adults whose mean age was 71. All were free of Alzheimer’s disease or other forms of dementia at the start of the study period, though some were showing signs of serious memory problems, including mild cognitive impairment, which can progress to full-blown dementia. More than a third of them were regularly taking vitamin D supplements.
Over the next 10 years, 2,696 of them developed Alzheimer’s disease or another form of dementia. Analysis of the data revealed that those who were taking vitamin D were 40 percent less likely to develop dementia than those who weren’t taking the supplements.
It didn’t matter which type of vitamin D supplement participants were taking. Some were taking vitamin D2, also known as ergocalciferol. Others were taking vitamin D3, also called cholecalciferol. Still others were taking vitamin D in combination with calcium. All three types of vitamin D appeared to lower dementia risk
The research team found that the potential benefits of vitamin D were greater in women than in men. In addition, vitamin D appeared to be less effective in people who already had mild cognitive impairment, or in those who carried the APOE-e4 gene, which raises the risk of developing Alzheimer’s disease. The findings were published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.
“We know that vitamin D has some effects in the brain that could have implications for reducing dementia,” said study author Zahinoor Ismail, though he noted that previous studies on vitamin D and dementia have had mixed 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.”
Earlier studies have found that low levels of vitamin D are linked to higher dementia risk, and that taking measures to assure you have adequate levels of vitamin D may help to keep the brain in good working order. The mechanism by which vitamin D may be beneficial for dementia is not clear, but some scientists have proposed that it may help to forestall the buildup of the toxic proteins beta-amyloid and tau in the brain, the two main hallmarks of Alzheimer’s disease.
The findings underscore the importance of identifying vitamin D deficiency, especially in older men and women. The vitamin is produced in the skin on exposure to sunlight; it is sometimes referred to as the “sunshine vitamin.”
The Recommended Dietary Allowance for vitamin D for adults ages 19 to 70 is 600 IU (15 mcg or micrograms) daily, and for those over 70 it is 800 IU (20 mcg) a day. The vitamin is often added to milk and other foods, and is also found in fish oils, regular consumption of which has also been linked to a lower risk of Alzheimer’s disease. But it may be hard to achieve those levels via foods alone, especially in the winter months, when sunlight levels are low. Your doctor can check your levels during a routine blood test.
Supplements can raise levels of vitamin D. But don’t take too much; excess levels can be hazardous. The upper limit for vitamin D in adults is 4,000 IU (100 mcg) a day.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Maryam Ghahremani, Eric E. Smith, Hung-Yu Chen, et al: “Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status.” Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, March 1, 2023
