As humans get older, NAD+ levels decrease, which means the body's defense enzymes and repair enzymes take a hit, and humans "succumb to aging," Sinclair said.
Harvard Medical School professor Sinclair — who has studied the relationship between NAD+ and aging — said in an interview with the YouTube channel Reverse Aging Revolution that the human body uses NAD+ as "a measure of adversity." As humans get older, NAD+ levels decrease, which means the body's defense enzymes and repair enzymes take a hit, and humans "succumb to aging," Sinclair said.