Nutraceuticals: 

Nicotinamide Riboside (NAD+ Precursors): A Comprehensive Review

Nicotinamide adenine dinucleotide (NAD+) is a coenzyme essential for cellular energy production, DNA repair, and metabolic regulation. NAD+ levels decline with aging, which may contribute to age-related conditions. NAD+ itself is not orally bioavailable, but precursor compounds—primarily nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN)—can be taken as supplements to increase NAD+ levels in blood and some tissues.

 

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Definitions and Terms Related to Pain

 

Levels of Confidence Summary

  • Safety and bioavailability: High (robust human data)[1][2][3][6]
  • Raising blood NAD+ levels: High (consistent across multiple trials)[2][3][6]
  • Fatigue/physical performance: Low to Moderate (one positive RCT, needs replication)[11]
  • Metabolic health/insulin sensitivity: Moderate (mixed results, population-specific)[1][19]
  • Cardiovascular health: Low to Moderate (early proof-of-concept only)[17]
  • Cognitive function/Alzheimer’s: Low to Moderate (promising preclinical, limited human data)[1][15][16]
  • Neuropathic pain: Low (preclinical only, no human trials)[7][8][9][10]
  • All other pain conditions: Low (preclinical only)

Recommendations

Consider NAD+ precursors as a safe but investigational intervention

  1. NAD+ precursors are safe for general use at recommended doses (250-500 mg/day)
  2. Evidence for clinical benefits in humans is limited but emerging
  3. Most promising for: afternoon fatigue/drowsiness in older adults, possibly metabolic health in specific populations
  4. Not recommended as a proven treatment for pain conditions (no human evidence)
  5. Consult your physician before use, especially if taking chemotherapy or diabetes medications

 

NAD+ Precursors: A Comprehensive Review

Introduction

Nicotinamide adenine dinucleotide (NAD+) is a coenzyme essential for cellular energy production, DNA repair, and metabolic regulation. NAD+ levels decline with aging, which may contribute to age-related conditions. NAD+ itself is not orally bioavailable, but precursor compounds can be taken as supplements to increase NAD+ levels in blood and some tissues:[1][2][3]

  • Nicotinamide riboside (NR)
  • Nicotinamide mononucleotide (NMN)

 

Important Context: While preclinical studies in animals show promising effects of NAD+ precursors on various health conditions, human clinical evidence remains limited. A comprehensive 2023 review concluded that “oral nicotinamide riboside supplementation has displayed few clinically relevant effects” in humans, with “an unfortunate tendency in the literature to exaggerate the importance and robustness of reported effects.” The efficacy of NAD+ precursors in humans is lower than expected from animal studies.[4][5]

Despite limited human studies, the use of NAD+ precursor supplements has grown quite popular. NAD+ precursors are available as dietary supplements, typically at doses of 250-1000 mg/day. They are safe and well-tolerated, with no serious adverse events reported in clinical trials.[1][6]

Evidence for Therapeutic Applications

Fatigue and Physical Performance

Evidence Level: Low to Moderate

A 12-week randomized controlled trial in 108 older Japanese adults (mean age 65 years) found that NMN 250 mg/day taken in the afternoon improved lower limb function (5-times sit-to-stand test) and reduced drowsiness, with moderate effect sizes (d = 0.72 and 0.64, respectively).[11] Benefits were most pronounced when NMN was taken in the afternoon rather than morning, and effects extended several days beyond treatment.[11]

However, comprehensive reviews note that while some studies suggest benefits for fatigue, small sample sizes limit interpretation and replication in larger trials is needed.[1]

Cognitive Function and Alzheimer’s Disease

Evidence Level: Low to Moderate

Preclinical Evidence:

    1. Multiple animal studies show NR/NMN reduce neuroinflammation, DNA damage, tau pathology, and improve cognitive function in mouse models of Alzheimer’s disease.[12][13][14]
    2. NMN activated autophagy and antioxidant pathways (Nrf2/Keap1/NQO1) in AD mice.[14]

Human Evidence:

    1. – Two small clinical trials showed improvements in plasma biomarkers and cognitive measures following NR supplementation in patients with cognitive impairment.[15]
    2. – A 2022 review concluded that while NAD+ precursors show promise for preventing cognitive decline, “further properly controlled clinical research is needed” as findings are primarily from animal models.[16]

Current Status:

Promising preclinical data, but limited human clinical evidence. Larger, longer-term trials are needed.[1][15]

 

Metabolic Health and Insulin Sensitivity

Evidence Level: Moderate (Mixed Results)

Positive Findings:

    1. One trial showed NMN improved muscle insulin sensitivity in prediabetic women (250 mg twice daily).[1]
    2. Early studies suggest modest improvements in blood pressure and arterial compliance.[17][18]

Negative Findings:

    1. A well-designed 12-week trial in 40 obese, insulin-resistant men found NR 1000 mg twice daily did NOT improve insulin sensitivity, glucose metabolism, body composition, or hepatic lipid content despite being safe and well-tolerated.[19]

Conclusion:

Results are inconsistent. NAD+ precursors may benefit some populations (e.g., prediabetic women) but not others (e.g., obese men). More research is needed to identify who might benefit.[1][18][20]

Cardiovascular Health

Evidence Level: Low to Moderate

Positive Findings:

Early proof-of-concept studies show NAD+ precursors are safe and may modestly improve:

    1. Blood pressure and arterial compliance
    2. Suppression of inflammatory activation in heart failure patients[17]

Important: These are surrogate markers, not hard clinical endpoints. No trials have demonstrated actual reduction in cardiovascular disease events or mortality. Larger clinical trials are needed to determine optimal populations, doses, and treatment duration.[17]

 

Pain Conditions

  1. Inflammatory Pain
  2. Sciatica
  3. Neuropathic Pain (Diabetic Neuropathy
  4. Chemotherapy-Induced Neuropathy

Evidence Level: Low (Preclinical Only)

  • No human clinical trials have evaluated NAD+ precursors for neuropathic pain relief.[7][8][9][10]
  • Animal studies show NR reduced pain behaviors in mouse models of diabetic neuropathy and rat models of paclitaxel-induced peripheral neuropathy.[8][9][10]
  • A 2025 study showed NR ameliorated trigeminal neuropathic pain in mice through mitochondrial restoration.[7]
  • Clinical translation remains unproven.

Multiple Sclerosis

Evidence Level: Low (Preclinical Only)

  • No human trials have evaluated NAD+ precursors for these pain conditions.
  • Evidence is limited to animal models.

Migraine

Evidence Level: Low (Preclinical Only)

  • No human trials have evaluated NAD+ precursors for these pain conditions.
  • Evidence is limited to animal models.

Other Conditions

  1. Anxiety, Depression
  2. Insomnia
  3. Gut Health
  • Evidence Level: Low (Preclinical Only)
  • No human clinical trials available for these conditions.

Safety Profile

NAD+ precursors (NR and NMN) have an excellent safety profile based on multiple human trials:[1][5][6]

  • Well-tolerated at doses up to 2000 mg/day for 8-12 weeks
  • No serious adverse events reported
  • No flushing (unlike niacin)
  • Mild gastrointestinal symptoms may occur at very high doses (>1000 mg/day)
  • No elevation of LDL cholesterol or dysregulation of metabolism
  • Safe in overweight/obese adults, older adults, and various patient populations

Cautions:

  • Limited data on long-term use (>12 weeks)
  • -heoretical concerns about interactions with chemotherapy (consult oncologist)
  • May affect diabetes medications (monitor blood glucose)

Formulations and Dosing

Enhanced Formulations:

Claims about liposomal and sublingual formulations providing “2-3-fold improved absorption” are not supported by published human studies. Standard oral NR/NMN capsules are effective at raising blood NAD+ levels.[2][3][6]

Standard Dosing:

  • NR or NMN: 250-500 mg/day for general use
  • Up to 1000 mg twice daily has been studied safely
  • Can be taken with or without food

Bioavailability:

  • Oral NR and NMN are bioavailable and dose-dependently increase blood NAD+ levels.[2][3][6]
  • Single doses of 100-1000 mg NR increased blood NAD+ by 22-142% in a dose-dependent manner.[6]
  • A single 1000 mg dose of NR increased blood NAD+ up to 2.7-fold in one individual.[2]

Important Metabolic Finding (2025):

Recent research shows that most orally administered NMN and NR undergoes gut microbiota-mediated conversion to nicotinic acid (NA), which then enters enterohepatic circulation and is preferentially used in the liver for NAD+ synthesis.[21] This explains why efficacy in humans may differ from animal studies and highlights the complexity of NAD+ metabolism.

Mechanisms of Action

NAD+ precursors help your cells produce energy more efficiently, reduce inflammation, support DNA repair, and may protect against age-related decline in various tissues. However, the extent of these benefits in humans is still being studied.

The details:

  1. Energy metabolism: Enhances mitochondrial NAD+ levels, supporting ATP production and oxidative phosphorylation
  2. Anti-inflammatory: Activates sirtuins (SIRT1, SIRT3), reduces pro-inflammatory cytokines (IL-6, TNF-α)
  3. Neuroprotection: Supports DNA repair via PARP activation, enhances BDNF expression, reduces oxidative stress
  4. Metabolic regulation: Activates AMPK, improves endothelial function, may enhance insulin signaling in some populations
  5. Cellular senescence: Reduces markers of cellular senescence and cGAS-STING pathway activation in preclinical models[12]

 

Synergies and Combinations

Theoretical (Not Clinically Validated):

Claims about synergies with metformin, statins, resveratrol, curcumin, cannabinoids, and acupuncture are not yet supported by clinical evidence and should be considered speculative at this time.

Levels of Confidence Summary

  • Safety and bioavailability: High (robust human data)[1][2][3][6]
  • Raising blood NAD+ levels: High (consistent across multiple trials)[2][3][6]
  • Fatigue/physical performance: Low to Moderate (one positive RCT, needs replication)[11]
  • Metabolic health/insulin sensitivity: Moderate (mixed results, population-specific)[1][19]
  • Cardiovascular health: Low to Moderate (early proof-of-concept only)[17]
  • Cognitive function/Alzheimer’s: Low to Moderate (promising preclinical, limited human data)[1][15][16]
  • Neuropathic pain: Low (preclinical only, no human trials)[7][8][9][10]
  • All other pain conditions: Low (preclinical only)

Critical Limitations

  1. Small sample sizes in most human trials limit interpretation of physiological outcomes[1]
  2. Short study durations (typically 8-12 weeks)
  3. Efficacy lower than expected from preclinical studies[4][5]
  4. Unclear whether blood NAD+ increases translate to tissue-level NAD+ repletion in target organs[5][17]
  5. Complex metabolism involving gut microbiota interactions[21]
  6. Need for biomarkers to identify individuals with NAD+ deficiency who might benefit most

Recommendations

Consider NAD+ precursors as a safe but investigational intervention

  1. NAD+ precursors are safe for general use at recommended doses (250-500 mg/day)
  2. Evidence for clinical benefits in humans is limited but emerging
  3. Most promising for: afternoon fatigue/drowsiness in older adults, possibly metabolic health in specific populations
  4. Not recommended as a proven treatment for pain conditions (no human evidence)
  5. Consult your physician before use, especially if taking chemotherapy or diabetes medications

References

  1. Dietary Supplementation With NAD+-Boosting Compounds in Humans: Current Knowledge and Future Directions. Freeberg KA, Udovich CC, Martens CR, Seals DR, Craighead DH. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences. 2023;78(12):2435-2448. doi:10.1093/gerona/glad106.
  2. An Open-Label, Non-Randomized Study of the Pharmacokinetics of the Nutritional Supplement Nicotinamide Riboside (NR) and Its Effects on Blood NAD+ Levels in Healthy Volunteers. Airhart SE, Shireman LM, Risler LJ, et al. PloS One. 2017;12(12):e0186459. doi:10.1371/journal.pone.0186459.
  3. Nicotinamide Riboside Is Uniquely and Orally Bioavailable in Mice and Humans. Trammell SA, Schmidt MS, Weidemann BJ, et al. Nature Communications. 2016;7:12948. doi:10.1038/ncomms12948.
  4. What Is Really Known About the Effects of Nicotinamide Riboside Supplementation in Humans. Damgaard MV, Treebak JT. Science Advances. 2023;9(29):eadi4862. doi:10.1126/sciadv.adi4862.
  5. NAD+ Precursors in Human Health and Disease: Current Status and Future Prospects. Yaku K, Nakagawa T. Antioxidants & Redox Signaling. 2023;39(16-18):1133-1149. doi:10.1089/ars.2023.0354.
  6. Safety and Metabolism of Long-Term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-Controlled Clinical Trial of Healthy Overweight Adults. Conze D, Brenner C, Kruger CL. Scientific Reports. 2019;9(1):9772. doi:10.1038/s41598-019-46120-z.
  7. Neuromodulation, Specialized Proresolving Mediators, and Resolution of Pain. Tao X, Lee MS, Donnelly CR, Ji RR. Neurotherapeutics : The Journal of the American Society for Experimental NeuroTherapeutics. 2020;17(3):886-899. doi:10.1007/s13311-020-00892-9.
  8. Specialized Pro-Resolving Lipid Mediators: A New Class of Non-Immunosuppressive and Non-Opioid Analgesic Drugs. Fattori V, Zaninelli TH, Rasquel-Oliveira FS, Casagrande R, Verri WA. Pharmacological Research. 2020;151:104549. doi:10.1016/j.phrs.2019.104549.
  9. Neuroinflammation, Oxidative Stress and Their Interplay in Neuropathic Pain: Focus on Specialized Pro-Resolving Mediators and NADPH Oxidase Inhibitors as Potential Therapeutic Strategies. Teixeira-Santos L, Albino-Teixeira A, Pinho D. Pharmacological Research. 2020;162:105280. doi:10.1016/j.phrs.2020.105280.
  10. Restoration of Mitochondrial Function Alleviates Trigeminal Neuropathic Pain in Mice. Yang J, Xie S, Guo J, et al. Free Radical Biology & Medicine. 2025;226:185-198. doi:10.1016/j.freeradbiomed.2024.11.011.
  11. Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults: A Randomized, Double-Blind Placebo-Controlled Study. Kim M, Seol J, Sato T, et al. Nutrients. 2022;14(4):755. doi:10.3390/nu14040755.
  12. NAD+ Supplementation Reduces Neuroinflammation and Cell Senescence in a Transgenic Mouse Model of Alzheimer’s Disease via cGAS-STING. Hou Y, Wei Y, Lautrup S, et al. Proceedings of the National Academy of Sciences of the United States of America. 2021;118(37):e2011226118. doi:10.1073/pnas.2011226118.
  13. NAD+ Supplementation Normalizes Key Alzheimer’s Features and DNA Damage Responses in a New AD Mouse Model With Introduced DNA Repair Deficiency. Hou Y, Lautrup S, Cordonnier S, et al. Proceedings of the National Academy of Sciences of the United States of America. 2018;115(8):E1876-E1885. doi:10.1073/pnas.1718819115.
  14. Therapeutic Effect of Nicotinamide Mononucleotide on Alzheimer’s Disease Through Activating Autophagy and Anti-Oxidative Stress. Ma RY, Li L, Yang H, et al. Biomedicine & Pharmacotherapy = Biomedecine & Pharmacotherapie. 2024;178:117199. doi:10.1016/j.biopha.2024.117199.
  15. Supplementation With NAD+ Precursors for Treating Alzheimer’s Disease: A Metabolic Approach. Alghamdi M, Braidy N. Journal of Alzheimer’s Disease : JAD. 2024;101(s1):S467-S477. doi:10.3233/JAD-231277.
  16. Supplementation With NAD and Its Precursors to Prevent Cognitive Decline Across Disease Contexts. Campbell JM. Nutrients. 2022;14(15):3231. doi:10.3390/nu14153231.
  17. Impact of Geroscience on Therapeutic Strategies for Older Adults With Cardiovascular Disease: JACC Scientific Statement. Forman DE, Kuchel GA, Newman JC, et al. Journal of the American College of Cardiology. 2023;82(7):631-647. doi:10.1016/j.jacc.2023.05.038.
  18. Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns. Bhasin S, Seals D, Migaud M, Musi N, Baur JA. Endocrine Reviews. 2023;44(6):1047-1073. doi:10.1210/endrev/bnad019.
  19. A Randomized Placebo-Controlled Clinical Trial of Nicotinamide Riboside in Obese Men: Safety, Insulin-Sensitivity, and Lipid-Mobilizing Effects. Dollerup OL, Christensen B, Svart M, et al. The American Journal of Clinical Nutrition. 2018;108(2):343-353. doi:10.1093/ajcn/nqy132.
  20. NAD+-Increasing Strategies to Improve Cardiometabolic Health?. Blanco-Vaca F, Rotllan N, Canyelles M, et al. Frontiers in Endocrinology. 2021;12:815565. doi:10.3389/fendo.2021.815565.
  21. Nicotinamide Riboside and Nicotinamide Mononucleotide Facilitate NAD+ Synthesis via Enterohepatic Circulation. Yaku K, Palikhe S, Iqbal T, et al. Science Advances. 2025;11(12):eadr1538. doi:10.1126/sciadv.adr1538.

Publications

  1. The therapeutic perspective of NAD+ precursors in age-related diseases – 2024
  2. Towards personalized nicotinamide mononucleotide (NMN) supplementation- Nicotinamide adenine dinucleotide (NAD) concentration – 2024
  3. Potential Synergistic Supplementation of NAD+ Promoting Compounds as a Strategy for Increasing Healthspan – 2023
  4. Ingestion of β-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adult – 2024
  5. The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults – 2023
  6. Research advances in the function and anti-aging effects of nicotinamide mononucleotide – 2024
  7. The Safety and Antiaging Effects of Nicotinamide Mononucleotide in Human Clinical Trials- an Update – 2023
  8. Role and Potential Mechanisms of Nicotinamide Mononucleotide in Aging – 2024
  9. Too old for healthy aging? Exploring age limits of longevity treatments – 2024

Emphasis on Education

 

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