What it is

NAD+ is a coenzyme made in every cell from vitamin B3 forms: niacin, nicotinamide, nicotinamide riboside and NMN. It exists as a pair, NAD+ and NADH, that flips back and forth as it carries electrons. Some enzymes use it and give it back. Others, the sirtuins, PARPs and CD38, consume it, so the cell must keep rebuilding it. Levels fall with age in muscle, skin, brain and blood, which is why it sits at the base of longevity work.