Nicotinamide Riboside (NR)
Salvage-pathway precursor of nicotinamide adenine dinucleotide (NAD+); converted to NMN by nicotinamide riboside kinases (NRK1/2) and then to NAD+ by NMNAT enzymes.
Nicotinamide Riboside (NR) is a vitamin B3 (niacin) form first characterized as a NAD+ precursor in the early 2000s. Among the available NAD+ boosters — nicotinamide, nicotinic acid, NMN — NR has been the most clinically studied, principally because it can be administered orally with established pharmacokinetics and is associated with documented elevations of whole-blood NAD+ across multiple trials.
Mechanistically, NR enters cells via dedicated nucleoside transporters and is phosphorylated by nicotinamide riboside kinase (NRK1 in most tissues, NRK2 in muscle) to nicotinamide mononucleotide (NMN), which is then adenylated by NMNAT enzymes to NAD+. NAD+ in turn drives the oxidoreductase reactions of glycolysis, the TCA cycle, oxidative phosphorylation, and the activities of NAD-consuming enzymes including SIRT1-7 (sirtuins), PARP1 (DNA repair), and CD38.
Clinical studies have reported modest improvements in metabolic and inflammatory markers with NR supplementation; the magnitude of phenotypic benefit in healthy adults remains debated, with the strongest signals appearing in older or metabolically compromised populations. NR is generally regarded as safe at studied doses (250-1000 mg/day). Comparative work on NR vs. NMN vs. direct NAD+ infusion is an active area.