Benefits
NAD+ elevation
Niagen® consistently and significantly raises whole blood and cellular NAD+ levels in human trials — with 300 mg/day producing ~50% increases and 1,000 mg/day producing 2-fold increases. NR is currently the most clinically studied oral NAD+ precursor with the most robust human pharmacokinetic data.
Metabolic health and insulin sensitivity
Human trials show NR improves liver fat content, reduces hepatic lipid accumulation, and improves insulin sensitivity markers in obese and metabolic syndrome populations. SIRT1/SIRT3 activation via elevated NAD+ drives mitochondrial efficiency improvements.
Cardiovascular and arterial health
A landmark University of Colorado trial showed NR supplementation reduced aortic stiffness by ~9% in middle-aged and older adults and lowered systolic blood pressure by ~8 mmHg — effects attributed to sirtuin-mediated improvements in vascular endothelial function.
Muscle function and physical performance
NR supplementation improved muscle mitochondrial function and reduced fatigue in middle-aged adults. Elevated NAD+ supports mitochondrial biogenesis via PGC-1α, improving muscle energy efficiency and recovery from exercise-induced damage.
Neuroprotection and cognitive aging
NR crosses the blood-brain barrier and elevates brain NAD+ levels. Preclinical data shows NR protects neurons from oxidative damage, reduces neuroinflammation, and maintains cognitive function in aging models. Human cognitive trial data is accumulating.
Mechanism of action
CD73-mediated cellular uptake
NR enters cells via nucleoside transporters and is phosphorylated by NR kinases (NRK1/2) to form NMN, which is then adenylylated to NAD+. This pathway bypasses the rate-limiting NAMPT step that limits nicotinamide (niacinamide) conversion — making NR one of the most efficient oral NAD+ precursors.
Sirtuin activation (SIRT1–7)
Elevated NAD+ activates all seven sirtuin deacylases simultaneously. SIRT1 and SIRT3 are particularly important — SIRT1 drives mitochondrial biogenesis via PGC-1α deacetylation, while SIRT3 protects mitochondria from oxidative damage and regulates metabolic enzymes.
PARP-1 and DNA repair
PARP-1 consumes NAD+ during DNA strand break repair. Chronically elevated PARP-1 activity (from accumulating DNA damage with age) depletes cellular NAD+, creating a vicious cycle. NR restores NAD+ substrate availability for both PARP-1 and sirtuins — two competing yet complementary longevity mechanisms.
Clinical trials
First-in-human dose-escalation study of nicotinamide riboside (Niagen®) at 100, 300, 1,000 mg/day for 8 weeks in 12 healthy adults. Outcomes: whole-blood NAD+, NAD+ metabolome. (Trammell et al. 2016, Nat Commun)
12 healthy adults. 8-week dose-escalation.
All doses dose-dependently elevated whole-blood NAD+. 300 mg/day: ~50% increase; 1,000 mg/day: ~140%. Foundational human PK trial confirming oral NR raises NAD+ levels. CRITICAL CAVEAT: NAD+ elevation is a biomarker — does NOT directly establish clinical benefits. The translation from elevated NAD+ to meaningful clinical outcomes (longevity, healthspan) remains an active research question with limited definitive human data.
Randomized, double-blind, crossover trial of NR (1,000 mg/day) vs placebo in 30 adults aged 55-79 with elevated SBP for 6 weeks each. (Martens et al. 2018, Nat Commun)
30 adults aged 55-79 with elevated BP.
NR reduced aortic pulse wave velocity (~9%) and systolic BP (~8 mmHg) vs placebo in those with stage 1 hypertension. Modest cardiovascular signal in this small trial. Independent replication needed.
RCT of NR (1,000 mg/day) vs placebo in overweight/obese adults with NAFLD for 12 weeks.
Overweight/obese NAFLD adults.
NR elevated liver NAD+, modestly reduced hepatic lipid content, improved markers of mitochondrial function. Note: NAFLD/MASLD landscape has been transformed by GLP-1 agonists (semaglutide, tirzepatide) and resmetirom (Rezdiffra® — FDA-approved 2024). NR adjunctive at most.
GRAS-affirmed safety trial examining NR supplementation (250-2,000 mg/day) in healthy adults for 8 weeks. (Conze et al. 2019, Sci Rep)
Healthy adults. Safety study.
No serious adverse effects at any dose up to 2,000 mg/day. No changes in liver enzymes, kidney function, lipids. Generally well-tolerated. Established NR safety profile for supplemental use.