NR (nicotinamide riboside) — The Efficient NAD+ Precursor
Nicotinamide riboside (NR) is a highly efficient precursor to NAD+, a critical coenzyme involved in cellular energy production, DNA repair, and sirtuin activation. By replenishing age-related declines in NAD+ levels, NR aims to support mitochondrial function and metabolic health.
Mechanism of Action
NR enters cells via specific transporters and is converted directly into nicotinamide mononucleotide (NMN) by the enzyme nicotinamide riboside kinase (NRK). NMN is subsequently converted to NAD+ by NMN adenylyltransferase (NMNAT). Elevated intracellular NAD+ levels activate sirtuins (particularly SIRT1 and SIRT3) and PARPs, which regulate mitochondrial biogenesis, oxidative stress responses, and DNA repair mechanisms. Unlike nicotinamide, NR does not inhibit sirtuin activity at high doses.
Human Trial Evidence
Multiple human clinical trials have demonstrated that oral NR supplementation safely and effectively increases whole-blood and skeletal muscle NAD+ levels. Studies have shown improvements in markers of metabolic health and reductions in circulating inflammatory cytokines in older adults, though evidence for extending human lifespan or significantly altering clinical disease outcomes remains limited.
Dosing Protocol
Clinical trials typically use doses ranging from 300 mg to 1,000 mg per day, often administered as nicotinamide riboside chloride. It is generally taken orally once or twice daily, with or without food. Higher doses up to 2,000 mg have been used in short-term studies without severe adverse effects, but 300 mg is the standard starting dose.
Safety & Contraindications
NR is generally well-tolerated with a strong safety profile in human trials up to 1,000 mg/day. Mild adverse effects can include nausea, fatigue, headaches, and gastrointestinal discomfort. Long-term safety data beyond a few months is still emerging, and its effects during pregnancy or in individuals with active cancer are not fully established.