I tend to view some of the processes involved with CFS to parallel (but are not identical) to Alzheimer’s Disease. Memory issues with CFS can remit with remission, AD has no remission.
Recently, the role of vitamin D with AD has had some research published (Journal Neurology, August 6, 2014). Low or very low Vitamin D levels double the risk of AD. CFS research has found that the severity of symptoms increases with low levels of vitamin D and greatly reduce when patients are at the top of the recommended range (or slightly beyond).
One form of vitamin D, 1,25D (not normally tested for) appears to go up or down depending on severity of CFS symptoms. By up, I mean very far above the normal range. When the lab did their first test of my 1,25 levels, it was so high they assumed a lab error. They repeated the test with the same result. With remission, I dropped down to the normal range of 1,25D.
A few years ago, there was a fad treatment, the Marshall Protocol, that promised remission if you pushed your Vitamin D level down to zero. Bad idea. I know many people who tried it that are still addressing side-effects that arose during their attempt to do this protocol (under MD supervision).
- Vitamin D and white matter abnormalities in older adults: a cross-sectional neuroimaging study
And many many more!
How much, technically that needs to be done in consultation with your MD. Most MDs will just want to get people into the bottom of the normal range. My physician wanted me to be near the top of the normal range. How much was I taking, around 20,000 IU of Vitamin D3 per day (as you get older, it takes more to maintain a level).