Losing your mind? Could be Vit D deficiency. Study on nursing home residents found twice the risk of dementia, Alzheimer’s and stroke in those low on Vit D. Despite the massive research on Vit D, we are still slow to adopt decent levels of supplementation. 2,000 is a pretty standard dose (and VERY cheap–don’t ever pay more than $20 for a year’s worth!) and it just goes up from there. I personally take 4,000 IU / day (due to a genetic uniqueness in my VDR receptor, for those who care) plus get good sun exposure.