NBC News - Living in a tree-filled neighborhood may be as beneficial to the heart as regular exercise, new research shows. Researchers at the University of Louisville designed a clinical trial that followed hundreds of people living in six low- to middle-income neighborhoods in South Louisville, Kentucky. They used blood and other samples to better understand how their heart risks changed before and after the team planted thousands of mature trees near their homes. Results from the Green Heart Louisville Project's HEAL Study, released Tuesday, showed that people living in neighborhoods with twice as many trees and shrubs had lower levels of a blood marker associated with heart disease, diabetes and some types of cancer compared with those who lived in more tree-bare neighborhoods.