What Is NAD+?

A coenzyme, not a nutrient

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every living cell. Coenzymes are small molecules that help enzymes carry out chemical reactions; NAD+’s particular specialty is acting as an electron carrier.[1][2] It exists in two interconverting forms — the oxidized form, NAD+, and the reduced form, NADH — and cells constantly shuttle between the two as part of normal metabolism.[1][2]

What NAD+ does in the cell

NAD+’s best-known role is in energy metabolism, where it helps convert the food you eat into ATP, the molecule cells use as an immediate energy source.[1][2] Beyond energy metabolism, NAD+ is also a required cofactor for several other enzyme families, including sirtuins (linked to cellular regulation) and PARPs (linked to DNA repair), as well as being consumed by enzymes such as CD38.[1][2] Dedicated pages on each of these enzyme families are planned for a later stage of this hub.

Where NAD+ comes from

The body builds its own NAD+ rather than absorbing it directly from food in meaningful amounts.[1][2] It does this through three overlapping biosynthetic routes, described in more detail on this hub’s page about how the body makes NAD+.

Can you just take NAD+ directly?

NAD+ itself is a relatively large, charged molecule, which affects how easily it can be absorbed intact when taken orally.[1][2] This is the main biochemical reason most oral products aimed at raising NAD+ levels use smaller precursor molecules, such as NMN or nicotinamide riboside (NR), rather than NAD+ itself. Other delivery formats exist in the market — including intravenous NAD+ infusions, which bypass this absorption question entirely by delivering NAD+ directly into the bloodstream; see NMN vs. NAD+ IV Therapy for what the human evidence actually shows for that route. This page focuses on NAD+ biology rather than any specific product category.