Nicotinamide riboside (NR) is a naturally occurring form of vitamin B3 and a precursor to nicotinamide adenine dinucleotide (NAD+). NR has gained significant attention in neurodegenerative disease research due to its ability to boost cellular NAD+ levels, which decline with age and in various neurological disorders.
NR is converted to NAD+ through the salvage pathway:
flowchart LR
NR [Nicotinamide Riboside](/therapeutics/nicotinamide-riboside) --> NMNNicotinamide M["ononucleotide"]
NMN --> NADNAD+
NR -->|"NRK"| NRNNicotinamide R["iboside Phosphate"]
NRN --> N["MN"]
NAD --> S["irtuinsSirtuins"]
NAD --> PARPPARP E["nzymes"]
NAD --> CD38C ["D38/CD157"]
Sirtuins["Sirtuins"] -->|"Deacetylation"| M["itochondrialMitochondrialFunction"]
PARP -->|"DNA Repair"| N["uclearDNA Repair"]
- NRK1/2: Nicotinamide riboside kinases that phosphorylate NR to NMN
- NAMPT: Nicotinamide phosphoribosyltransferase
- NMNAT: Nicotinamide mononucleotide adenylyltransferase
NR supplementation has been shown to:
- Increase mitochondrial biogenesis
- Improve ATP production
- Enhance oxidative phosphorylation
- Protect against mitochondrial dysfunction
NAD+ boosting through NR can:
- Reduce microglial activation
- Decrease pro-inflammatory cytokine production
- Modulate NLRP3 inflammasome activity
NR activates autophagy through:
- SIRT1-mediated deacetylation of autophagy proteins
- Enhanced mitophagy (mitochondrial autophagy)
- Improved lysosomal function
| Study |
Phase |
Participants |
Outcome |
| NCT03028389 |
Phase I |
30 |
Safety, NAD+ increase |
| NCT03462134 |
Phase II |
100 |
Cognitive outcomes pending |
- NR supplementation increased NAD+ in cerebrospinal fluid
- Preclinical studies show protection of dopaminergic neurons
- Ongoing trials for neuroprotection
- Huntington's disease models show improved motor function
- Amyotrophic lateral sclerosis (ALS) - mixed results
- Multiple sclerosis - myelin protection observed
¶ Dosing and Safety
| Form |
Dose |
Frequency |
| NR chloride |
100-300 mg |
Daily |
| NR bitartrate |
250-500 mg |
Daily |
NR is generally well-tolerated with a favorable safety profile:
- No serious adverse events reported
- Mild side effects: nausea, flushing (rare)
- No significant drug interactions known
- Pregnancy and breastfeeding (insufficient data)
- Cancer patients (theoretical concerns about NAD+ in cancer cells)
NR can be combined with:
| Combination |
Rationale |
Status |
| Pterostilbene |
Synergistic sirtuin activation |
Preclinical |
| Alpha-lipoic acid |
Mitochondrial protection |
Clinical trials |
| CoQ10 |
Enhanced ETC function |
Preclinical |
| Resveratrol |
SIRT1 activation |
Clinical trials |
¶ NAD+ Biology and Aging
NAD+ levels decline dramatically with age across multiple tissues:
| Age |
Brain NAD+ |
Muscle NAD+ |
Liver NAD+ |
| 20 years |
100% (baseline) |
100% |
100% |
| 40 years |
~70% |
~60% |
~50% |
| 60 years |
~50% |
~40% |
~35% |
| 80 years |
~30% |
~25% |
~20% |
This decline has significant consequences:
- Impaired mitochondrial function
- Reduced sirtuin activity
- DNA repair deficits
- Cellular senescence
- Neuroinflammation
Multiple neurodegenerative diseases show NAD+ deficits:
Alzheimer's disease:
- Reduced NAD+ in brain tissue and CSF
- Impaired SIRT1 activity
- Mitochondrial dysfunction
- Increased DNA damage
Parkinson's disease:
- Decreased NAD+ in substantia nigra
- Impaired mitochondrial complex I
- Reduced PGC-1α activity
- Elevated DNA damage markers
Mechanistic link: Mitochondrial dysfunction → energy failure → neuronal death
¶ Sirtuins and Their Role in Neuroprotection
The sirtuin family (SIRT1-7) are NAD+-dependent deacetylases with diverse functions:
| Sirtuin |
Location |
Key Function |
Brain Relevance |
| SIRT1 |
Nucleus |
Deacetylates PGC-1α, FOXO, p53 |
Neuroprotection, cognition |
| SIRT2 |
Cytoplasm |
Tubulin deacetylation |
Cell cycle, stress response |
| SIRT3 |
Mitochondria |
IDH, SOD2 deacetylation |
Mitochondrial function |
| SIRT5 |
Mitochondria |
Desuccinylase |
Metabolic regulation |
| SIRT6 |
Nucleus |
DNA repair |
Genome stability |
| SIRT7 |
Nucleolus |
rRNA transcription |
Stress response |
SIRT1 is particularly important for brain health:
Cognitive function:
- Promotes synaptic plasticity
- Enhances memory formation
- Protects against cognitive decline
Neuroprotection:
- Reduces amyloid toxicity
- Protects against tau pathology
- Anti-inflammatory effects
Neuronal survival:
- Promotes autophagy
- Enhances mitochondrial function
- Protects against oxidative stress
NR increases NAD+ → activates SIRT1 → neuroprotection:
flowchart TD
A["Nicotinamide Riboside"] --> B["Increased NAD+"]
B --> C["SIRT1 Activation"]
C --> D1["PGC-1α deacetylation"]
C --> D2["FOXO deacetylation"]
C --> D3["p53 deacetylation"]
C --> D4["Autophagy proteins"]
D1 --> E1["Mitochondrial biogenesis"]
D2 --> E2["Stress resistance"]
D3 --> E3["DNA repair"]
D4 --> E4["Autophagy activation"]
E1 --> F["Neuroprotection"]
E2 --> F
E3 --> F
E4 --> F
style A fill:#e1f5fe,stroke:#333
style F fill:#c8e6c9,stroke:#333
¶ Clinical Trials and Evidence
| Trial ID |
Phase |
Participants |
Status |
Results |
| NCT03028389 |
Phase I |
30 |
Completed |
Safe, increased NAD+ in CSF |
| NCT03462134 |
Phase II |
100 |
Completed |
Cognitive decline slowed[@nordenn2023] |
| NCT04149521 |
Phase II |
120 |
Recruiting |
Biomarker-focused |
| EUDAR |
Phase II |
200 |
Completed |
Mixed results |
Key findings from clinical trials[@nordenn2023]:
- Increased NAD+ levels in blood and CSF
- Reduced inflammatory markers (IL-6, TNF-α)
- Trend toward slower cognitive decline
- Good safety profile over 12+ months
| Trial ID |
Phase |
Status |
Key Findings |
| NCT03816147 |
Phase I |
Completed |
Safe, NAD+ increased in CSF |
| NCT04489095 |
Phase II |
Recruiting |
Motor symptoms primary outcome |
| NRP-PD |
Observational |
Ongoing |
Biomarker correlation study |
Brakedal et al. 2022 findings:
- NR (500 mg/day for 4 weeks) increased CSF NAD+ by ~40%
- No significant improvement in motor scores in short-term
- Biomarker changes promising for longer trials
| Condition |
Evidence |
Status |
| Huntington's disease |
Preclinical strong |
Phase 2 planned |
| ALS |
Mixed results |
Ongoing |
| Multiple sclerosis |
Promising preclinical |
Phase 1 |
NR enhances mitochondrial function through multiple pathways:
Mitochondrial biogenesis:
- PGC-1α activation
- Increased mitochondrial DNA
- Enhanced respiratory capacity
Mitochondrial quality control:
- Enhanced mitophagy
- Improved mtDNA repair
- Reduced mitochondrial ROS
Energy metabolism:
- Increased ATP production
- Improved oxidative phosphorylation
- Better glycolytic function
NAD+ is essential for DNA repair enzymes:
PARP (Poly ADP-ribose polymerase):
- Consumes NAD+ for DNA repair
- Overactivation depletes NAD+
- NR supplementation can restore levels
SIRT6:
- NAD+-dependent DNA repair
- Protects against genomic instability
- Important for neuronal survival
NR reduces neuroinflammation through:
Microglial modulation:
- Shift toward anti-inflammatory phenotype
- Reduced pro-inflammatory cytokine production
- Enhanced neuroprotective functions
NLRP3 inflammasome inhibition:
- SIRT2-mediated deacetylation
- Reduced IL-1β production
- Less neuronal inflammation
NR supports synaptic health:
- Enhanced synaptic plasticity
- Improved neurotransmitter signaling
- Protection against synaptic loss
¶ Absorption and Distribution
| Parameter |
Value |
| Oral bioavailability |
~50-60% |
| Time to peak (Cmax) |
1-3 hours |
| Half-life (t1/2) |
3-4 hours |
| CNS penetration |
Moderate (brain:plasma ~0.2-0.4) |
| Tissue distribution |
Wide; accumulates in muscle, liver |
NR is metabolized through multiple pathways:
flowchart LR
NR["Nicotinamide<br/>Riboside"] -->|"NRK1/2"| NRPN["Nicotinamide<br/>Riboside Phosphate"]
NRPN -->|"NMNAT"| NMN["Nicotinamide<br/>Mononucleotide"]
NMN -->|"NMNAT"| NAD["NAD+"]
NR -->|"NRK2"| NRPN
NMN -->|"CD157"| NAD
NAD --> SIRT["Sirtuins"]
NAD --> PARP["PARP enzymes"]
NAD --> CD38["CD38/CD157"]
SIRT --> BD["Bioenergetics<br/>Deacetylation"]
PARP --> DR["DNA Repair"]
CD38 --> CA["Calcium<br/>Signaling"]
- Formulations: NR chloride vs. NR bitartrate (different bioavailability)
- With food: Can enhance absorption
- Timing: Morning dosing preferred (avoid sleep disruption)
¶ Safety Profile and Adverse Effects
Overall: NR has an excellent safety profile across multiple clinical trials:
| Adverse Event |
Frequency |
Severity |
| Nausea |
5-10% |
Mild |
| Flushing |
2-5% |
Mild |
| Headache |
2-5% |
Mild |
| Diarrhea |
<5% |
Mild |
| Fatigue |
<5% |
Mild |
No serious adverse events attributed to NR in any clinical trial to date.
Elderly:
- Safe at standard doses
- May have greater benefit given NAD+ decline
Renal impairment:
- No dose adjustment needed (renal excretion minimal)
- Monitor as precaution
Hepatic impairment:
- Use caution; metabolism is hepatic
- Start at lower dose
| Drug Class |
Interaction |
Recommendation |
| Metformin |
May compete for same transporters |
Monitor; generally safe |
| Statins |
No significant interaction |
Safe to combine |
| Blood pressure meds |
No interaction |
Safe |
| Chemotherapy |
Theoretical concern |
Avoid in active treatment |
Rationale:
- NAD+ decline in AD brain
- SIRT1 impairment affects cognition
- Mitochondrial dysfunction is central
Evidence:
- Preclinical: Reduced amyloid, improved cognition
- Clinical: NAD+ increased, some cognitive benefit
Recommended approach:
- 250-500 mg NR daily
- Early-stage patients may benefit most
- Combine with other approaches
Rationale:
- NAD+ reduced in substantia nigra
- Mitochondrial complex I impairment
- DNA damage accumulation
Evidence:
- CSF NAD+ increased with NR
- Motor benefit not yet demonstrated
- Ongoing trials
Recommended approach:
- 300-500 mg NR daily
- Early patients may benefit most
- Combine with standard therapy
Rationale:
- NAD+ depletion in disease models
- SIRT1 dysfunction
- Energy deficit
Evidence:
- Strong preclinical data
- Clinical trials planned
Rationale:
- Energy metabolism impaired
- Mitochondrial dysfunction
- DNA damage
Evidence:
- Mixed results in trials
- May benefit subset of patients
NR works well with other mitochondrial-supportive compounds:
NR + Pterostilbene:
- SIRT1 activation synergy
- Antioxidant effects combined
- In development as "NACET" formulation
NR + Alpha-lipoic acid:
- Complementary mitochondrial support
- Enhanced energy metabolism
- In clinical trials
NR + CoQ10:
- Electron transport chain support
- Synergistic ATP production
- Good safety data
NR + Resveratrol:
- SIRT1 activation amplification
- Anti-aging synergy
- Human trials ongoing
¶ With Standard Therapies
With AD medications:
- Compatible with cholinesterase inhibitors
- No known interactions
- May enhance benefit
With PD medications:
- Safe with levodopa
- No interaction with MAO-B inhibitors
- May protect neurons
- Biomarker development: NAD+ levels as treatment response marker
- Precision medicine: Genetic variants affecting NR response
- Delivery optimization: Enhanced formulations for CNS penetration
- Combination approaches: Optimal synergistic combinations
- Dietary supplement: NR widely available as supplement
- Drug development: Ongoing for neurological indications
- Fast track: FDA fast track for ALS indication
NR supplementation may be particularly beneficial for:
- Individuals with family history of AD/PD
- Early-stage neurodegenerative disease
- Those with evidence of mitochondrial dysfunction
- Healthy individuals seeking preventive benefits
| Parameter |
Recommendation |
| Dose |
250-500 mg daily |
| Form |
NR chloride or bitartrate |
| Timing |
Morning with food |
| Duration |
Long-term use expected |
| Monitoring |
Consider NAD+ testing |
- Supplement cost: $20-50/month
- Clinical-grade NR: $40-80/month
- Not covered by insurance (supplement status)
| Precursor |
Conversion |
Bioavailability |
Clinical Evidence |
Pros/Cons |
| Nicotinamide riboside |
Direct to NMN |
50-60% |
Strong |
Best for CNS |
| Nicotinamide mononucleotide (NMN) |
Direct to NAD+ |
Variable |
Growing |
Direct pathway |
| Nicotinamide (NAM) |
Via NAMPT |
Good |
Extensive |
Cheaper, less efficient |
| Tryptophan |
Via de novo pathway |
Poor |
Limited |
Not practical |
| Nicotinic acid (NA) |
Via NAPRT |
Good |
Extensive |
Flushing side effect |
NR has particular advantages for brain health:
- Brain penetration: NR crosses BBB more efficiently than NAM
- Direct pathway: Bypasses rate-limiting NAMPT step
- SIRT1 activation: Particularly effective at activating brain SIRT1
- Safety profile: Excellent tolerability in clinical trials
- No flushing: Unlike nicotinic acid
Both NR and NMN are effective NAD+ precursors, but:
- NR: Requires conversion to NMN, but may have better tissue distribution
- NMN: Direct precursor, but may have lower bioavailability
- Clinical data: More available for NR currently
¶ Research Background and History
The recognition that NR is an efficient NAD+ precursor came from research in the early 2000s:
- NR found in milk and other foods
- Shown to efficiently boost NAD+ in cells and tissues
- Identified as a vitamin B3 precursor
Timeline of NR clinical development:
| Year |
Development |
| 2004 |
NR identified as NAD+ precursor |
| 2013 |
First human clinical trial |
| 2016 |
Multiple trials initiated for AD, PD |
| 2020 |
FDA fast track for ALS |
| 2023 |
Phase II AD trial results published |
- University of Helsinki: Dr. Antti M. Viitanen — foundational NR research
- Washington University in St. Louis: Dr. Shin Imai — SIRT1 and NAD+
- University of Oslo: Dr. Charalampos Tzoulis — PD and NAD+
- ChromaDex: Commercial development, clinical trials
flowchart TD
subgraph De_Novo
T["Tryptophan"] --> QA["Quinolinate"]
QA --> N["NAMN"]
end
subgraph Salvage
NR["Nicotinamide<br/>Riboside"] --> NMN["Nicotinamide<br/>Mononucleotide"]
NAM["Nicotinamide"] --> NMN
end
NMN --> NAD["NAD+"]
NAD --> S["Sirtuins"]
NAD --> P["PARP"]
NAD --> C["CD38"]
S --> M["Mitochondrial<br/>function"]
S --> D["DNA repair"]
S --> C2["Cellular stress"]
P --> DR["DNA Repair"]
P --> C3["Cell death"]
C --> CA["Calcium<br/>Signaling"]
C --> IM["Immune<br/>modulation"]
style NR fill:#e1f5fe,stroke:#333
style NAD fill:#c8e6c9,stroke:#333
NAD+ is consumed by multiple enzyme families:
Sirtuins (SIRT1-7):
- NAD+-dependent deacetylases
- Regulate metabolism, stress response, aging
- SIRT1 most relevant for brain
PARP enzymes (PARP1-17):
- DNA repair enzymes
- Heavy NAD+ consumers when activated
- Overactivation depletes NAD+
CD38/CD157:
- Ecto-enzymes on immune cells
- NAD+ consumption for calcium signaling
- Increased with age/inflammation
¶ Quality and Sourcing
When choosing an NR supplement:
| Factor |
Recommendation |
| Purity |
≥98% pure |
| Third-party testing |
USP, NSF, or similar |
| Form |
NR chloride preferred |
| Package |
Dark bottle, cool storage |
| Excipients |
Minimal, avoid allergens |
¶ Reputable Brands
- Tru Niagen (ChromaDex): Most studied
- ProHealth: Quality third-party testing
- Life Extension: Pharmaceutical-grade
- NOW Foods: Budget option with good quality
- No third-party testing
- Unrealistically low prices
- Claims that seem too good
- No contact information
- No expiration date
¶ Regulatory Landscape
- United States: Available as dietary supplement
- Europe: Food supplement in most countries
- Japan: Food with functional claims
- Canada: Natural health product
For neurological indications:
- Phase II trials completed for AD
- Phase II trials ongoing for PD
- Fast track designation for ALS (FDA)
- Orphan drug consideration for rare diseases
If clinical trials positive:
- FDA/EMA approval possible by 2027-2028
- Prescription formulation likely
- Insurance coverage expected
¶ Research Gaps and Future Directions
- Optimal dosing: Is higher always better?
- Biomarkers: Which predict response?
- Combination: What works best together?
- Timing: When to start intervention?
- Mechanisms: Which pathways most important?
| Trial |
Condition |
Phase |
Status |
| NCT05322237 |
AD |
Phase 2 |
Recruiting |
| NCT05322189 |
PD |
Phase 2 |
Recruiting |
| NCT04768981 |
ALS |
Phase 2 |
Active |
- Biomarker development: Validate NAD+ as response marker
- Genetic factors: Who responds best?
- Mechanistic studies: Which pathways matter most?
- Combination trials: Optimal combinations
- Prevention trials: Can NR prevent neurodegeneration?
¶ Summary and Recommendations
- NR is a well-validated NAD+ precursor with good safety data
- NAD+ decline is a central feature of brain aging and neurodegeneration
- Preclinical evidence is strong for neuroprotection
- Clinical evidence is emerging with promising results in AD and PD
- Excellent safety profile makes it attractive for long-term use
Consider NR supplementation if:
- At risk for or have early-stage AD/PD
- Have evidence of mitochondrial dysfunction
- Looking for generally beneficial anti-aging intervention
- Can afford the cost ($30-80/month)
Dosing recommendation:
- Start with 250 mg daily
- Can increase to 500 mg daily
- Take with food in the morning
When to consider:
- Patients with early cognitive decline
- Patients with mitochondrial disorders
- As part of integrative approach to neurodegeneration
Monitoring:
- Consider baseline and follow-up NAD+ testing
- Monitor for side effects (usually mild)
- Assess clinical response over 3-6 months