Exercise increases circulation in the body and helps bring more oxygen, glucose and other needed substances to the brain.

WSJ: Exercise Might Beat Puzzles for Protecting the Aging Brain

To find the body's secret weapon, scientists remove cells from a lymph node - a part of the circulation system used by immune cells, but which also often forms a "staging post" for cancer as it spreads around the body.

BBC: Supercharged cells fired at skin cancer

"There is a significant body of scientific and clinical evidence supporting the safety and efficacy of ginkgo extract for both cognitive function and improved circulation, " said Mark Blumenthal, executive director of the American Botanical Council.

CNN: Five ways to keep Alzheimer's away