Nicotinamide Riboside (NR) — The NAD+ Precursor
Nicotinamide riboside (NR) is a form of vitamin B3 and a direct precursor to NAD+. Along with NMN, it is the most studied NAD+ precursor in humans. NR is converted to NMN and then to NAD+ via the Preiss-Handler pathway. Multiple human RCTs confirm NR safely and significantly elevates blood NAD+ levels.
Mechanism of Action
NR is taken up by cells and phosphorylated to NMN by NRK1/2 (nicotinamide riboside kinases), then to NAD+ by NMNAT enzymes. Elevated NAD+ activates sirtuins (SIRT1-7) and PARP enzymes, driving DNA repair, mitochondrial biogenesis, and metabolic regulation. NR may have slightly different tissue distribution than NMN, with potentially greater liver uptake.
Human Trial Evidence
A 2018 Nature Communications RCT (Martens et al.) showed 1,000 mg/day NR for 6 weeks safely elevated whole-blood NAD+ by 60% in healthy middle-aged adults. A 2019 Cell Metabolism RCT showed NR improved mitochondrial function in skeletal muscle of older adults. A 2020 Science Translational Medicine trial showed NR reduced liver fat in NAFLD patients.
Dosing Protocol
250–1,000 mg/day. Most human trials use 500–1,000 mg/day. Best taken in the morning. Crystalline NR (Tru Niagen/ChromaDex) is the most studied form. NR vs NMN debate: NR may be better for liver; NMN may be better for muscle and brain. Some practitioners combine both at lower doses.
Safety & Contraindications
Excellent safety profile. Well-tolerated up to 2,000 mg/day in trials. Mild flushing less common than with niacin. May cause mild GI effects at high doses. Same theoretical cancer concern as NMN (NAD+ fuels PARP1). No significant drug interactions. Safe for long-term use.
Key Papers
Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults
Nature Communications · 2018
Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures
Cell Reports · 2019