The reviewed research included 1658 elderly participants who were free from dementia at the start of the study(Littlejohns TJ et al. 2014). The vitamin they were tested for was vitamin D. During the average follow-up of 5.6 years, 171 participants developed dementia including 102 cases of Alzheimer's disease. The researchers concluded that the results confirmed that vitamin D deficiency is associated with a substantially increased risk for dementia and Alzheimer's disease. In my experience, just by taking 2000 IU of vitamin D 3 per day would keep you above the level of what this research indicates as increased risk for dementia. Find our Vitamin D formula here.
Littlejohns TJ, Henley WE, Lang IA, Annweiler C, Beauchet O, Chaves PH, Fried L, Kestenbaum BR, Kuller LH, Langa KM, Lopez OL, Kos K, Soni M, Llewellyn DJ. Vitamin D and the risk of dementia and Alzheimer disease. Neurology. 2014 Sep 2;83(10):920-8. doi: 10.1212/WNL.0000000000000755. Epub 2014 Aug 6.