Shedding light on risk factors for dementia is one of the most important tasks facing today’s health researchers, and the relationship between diet and dementia is of increasing interest.
Some studies have suggested that a lack of vitamin D may be linked to an increased risk of Alzheimer’s disease, but a new larger UK study published this week has found a stronger relationship than previously suggested.
What did new research find?
The study involved 1,658 Americans over the age of 65 who had no history of dementia, cardiovascular disease or stroke. The researchers measured vitamin D in their blood and then followed their cognitive health for an average of six years. During that time, 171 participants developed dementia, of which 102 developed Alzheimer’s disease.
According to the research, those with low levels of vitamin D in the blood were 53 per cent more likely to develop any form of dementia, and those with vitamin D deficiencies were at a 125 per cent greater risk. Similar results were reported specifically for Alzheimer’s disease. People with low levels of vitamin D were nearly 70 per cent more likely to develop the condition, and those with deficiencies were over 120 per cent more likely to do so. Thus older people with very low vitamin D levels could be more than twice as likely to develop any kind of dementia.
Sources of vitamin D
Vitamin D comes from three main sources: exposing the skin to sunlight, foods rich in vitamin D, such as oily fish, eggs, fortified cereals and fat spreads, and vitamin supplements. As there are few sources in the diet, sunlight is important. However, older people’s skin can be less efficient at making the vitamin, and they may be more at risk of low sun exposure because of poor mobility/disability, making them more reliant on other sources.
What do the findings mean for people worried about dementia?
This type of study cannot show that low vitamin D is a cause of dementia. We cannot yet conclude that increasing vitamin D intake would help prevent dementia. Clinical trials are needed to test directly whether boosting vitamin D levels by eating foods such as oily fish, or encouraging those who are deficient to take vitamin D supplements, can reduce the risk of Alzheimer’s disease and dementia. In the meantime, as adequate vitamin D is important for bone health, we should ensure that we, or the people we care for, go outside for at least a short period of time in the summer sun and eat foods rich in vitamin D. For those aged 65 years and over and people not exposed to much sun the Department of Health recommends a daily supplement containing 10 micrograms (0.01mg) of vitamin D.
