All data have been accrued for the healthy aging aim, which included healthy people age 18-22 and age 70-89. To study the second aim, 23 patients with AD will be recruited from the Minneapolis, MN VA medical center. 23 age - and gender- matched controls will be recruited to study neurodegenerative disease associated demand on the antioxidant system. We do NOT currently have the resources to screen candidates with AD who are not current patients at the VA medical center in Minneapolis.