18 Bring me sunshine The role of Vitamin D
One key factor in cognitive function is Vitamin D. “Low levels are associated with cognitive decline,” says Dr Bredesen. Yet, approximately 25pc of Irish people over the age of 50 are deficient in Vitamin D in winter, according to research carried out for the TILDA study at Trinity College Dublin. And there are wide variations across the country with those in the north and west most likely to be low in the vitamin.
“Vitamin D does appear to be a mood enhancer so it certainly has some role to play in the production of serotonin,” says Dr Briffa. “There is a bit of work in this area but what I’ve found is that when people optimise their levels of vitamin D, they have either no, or far fewer, issues around mood through the winter. They feel a lot better mentally and they also get fewer infections.”
That is because Vitamin D also boosts immunity which, says Dr Amen, is crucial to brain function. He cites an editorial by 33 clinicians and researchers published in the Journal of Alzheimer’s in 2016 that expressed concern that the role of viruses, bacteria and fungal infections was being overlooked as a major cause of cognitive dysfunction and Alzheimer’s. Other studies have found the oral bacteria associated with gum disease (Porphyromonas gingivalis) repeatedly in the brains of those with Alzheimer’s. They suggest that these infectious agents remain latent in the brain and can be reactivated when the body is under stress or the immune system weakens with age. In these cases, believes Bredesen, Alzheimer’s can be seen as the brain’s protective response to the pathogens.
“The simple thing to do,” says Dr Amen, “is boost your immunity to get your body to want to fight infections and the way to do that is to optimise your Vitamin D levels.”
Vitamin D is made in the body when your skin is exposed to UVB rays. Of course, we’re all aware now of the dangers of sun exposure and the need to wear sun protection, but Dr Amen points out that dermatologists have “made us afraid of the sun”. “Low levels of sun exposure are as harmful as high levels of sun exposure. So I don’t want you to get burned, but I want you to know your Vitamin D level and to optimise either with more sun in a sane, healthy way or by taking Vitamin D3.”
Your GP can run a blood test to determine your levels, normal is estimated as between 20-50ng/ml, but both Dr Bredesen and Dr Amen recommend optimising levels at between 50-80ng/ml. Retest regularly, though, as too much Vitamin D can be toxic.