Two recent studies indicate that vitamin D intake can have a significant effect on the cognitive abilities of the elderly. Unfortunately, more than half of older Americans have insufficient levels of vitamin D, according to David Llewellyn, Ph.D., a researcher at the University of Exeter Peninsula Medical School, United Kingdom. Llewellyn presented data on this topic from the Third National Health and Nutrition Examination Survey, or NHANES III, during the Alzheimer's Association International Conference on Alzheimer's Disease 2010, July 10-15 in Honolulu.