Nicotinamide adenine dinucleotide — a coenzyme found in every living cell that ferries electrons through energy metabolism and fuels the enzymes behind DNA repair and cellular defense. Levels decline significantly with age.
NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every living cell — not a peptide, but studied heavily alongside peptides in longevity and cellular-energy research. It's central to how cells convert food into usable energy, and it's required by many of the enzymes that keep cells' DNA and antioxidant defenses in working order.
NAD+ is best known as an electron carrier: in its reduced form (NADH), it delivers electrons to the first complex of the mitochondrial electron transport chain, the process that generates most of a cell's ATP. But NAD+ is also a required cofactor for enzymes that have nothing to do with energy production directly.
As NAD+ cycles to NADH and back, it shuttles electrons through the reactions that break down food into usable energy — the core of cellular respiration.
Sirtuins (SIRT1–5) are NAD+-dependent enzymes tied to DNA-damage defense, antioxidant pathways, and repair, and are studied for their association with healthy aging across multiple species. Without enough NAD+ on hand, sirtuin activity drops.
Poly(ADP-ribose) polymerase (PARP) is a separate DNA-repair enzyme that also depends on NAD+. Repairing DNA damage consumes NAD+, so researchers note that heavy or ongoing DNA damage can deplete the pool available for other NAD+-dependent jobs.
Most human-facing research uses NAD+ precursors (such as NR or NMN) or IV administration rather than NAD+ itself, since direct cellular uptake of NAD+ is limited.
Peptide Curious provides educational and editorial content only. It is not medical advice and is not a substitute for a qualified healthcare professional. NAD+ is discussed here as a research compound; content may describe emerging research not approved for clinical use.