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Peptide Database

Longevity & cellular research

NAD+ (Nicotinamide Adenine Dinucleotide): Research, Mechanism & Current Evidence

Coenzyme central to cellular energy production, widely studied in ageing and metabolism research.

Also known as nicotinamide adenine dinucleotide · NAD · Nicotinamide Adenine Dinucleotide

Research use onlyStrongest evidence: controlled clinical trialReviewed
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What is NAD+?

NAD+ is not a peptide. It is a coenzyme — a small helper molecule — present in every cell, where it carries electrons during the reactions that convert food into usable energy.

It is included in this database because it appears constantly in longevity research and is frequently discussed alongside peptides, not because it belongs to the same chemical class.

What is NAD+ researched for?

The central observation driving the field is that NAD+ levels fall with age in several tissues, and that restoring them improves measures of function in older animals.

Most human research studies precursors — nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) — rather than NAD+ itself, because precursors are absorbed more readily.

  • Restores NAD+ levels for optimal ATP synthesis
  • Enhances glucose and fat metabolism
  • Improves oxygen utilization and endurance
  • Activates PARP enzymes for genomic stability
  • Supports longevity pathways
  • May help clear senescent cells
  • Improves mental clarity and focus
  • Supports neuronal health and function

How does NAD+ work?

NAD+ is consumed by two families of enzymes that matter in ageing research: sirtuins, involved in DNA repair and metabolic regulation, and PARPs, involved in repairing DNA damage. Both need NAD+ to work, so falling NAD+ constrains them.

Raising NAD+ is therefore studied as a way of removing that constraint rather than as a direct effect in itself.

What does the research show?

Human trials of NR and NMN reliably show that blood NAD+ levels rise. What has been much harder to demonstrate is that this produces meaningful clinical change: trials of physical function, insulin sensitivity and inflammation have produced mixed and often null results.

Animal studies are considerably more positive than human studies, which is a pattern worth noting rather than explaining away.

Limitations of the current evidence

The gap between 'raises a biomarker' and 'improves an outcome' is the central unresolved issue in this field.

Intravenous NAD+ administration in particular has very little controlled evidence behind it despite widespread commercial use.

References

  1. NAD+ and sirtuins in aging and disease

    Imai S, Guarente L · Trends in cell biology · 2014

    Seminal review establishing that NAD+ decline is central to aging, driving defects in sirtuin-mediated nuclear and mitochondrial functions and resulting in age-associated pathologies.

    PMID 24786309

  2. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD(+) in healthy middle-aged and older adults

    Martens CR, Denman BA, Mazzo MR, et al. · Nature communications · 2018

    Randomized crossover trial showing NR (1000 mg/day for 6 weeks) is well tolerated and effectively elevates NAD+ in healthy middle-aged and older adults, with preliminary evidence for reduced blood pressure and arterial stiffness.

    Controlled clinical trial · PMID 29599478

  3. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women

    Yoshino M, Yoshino J, Kayser BD, et al. · Science (New York, N.Y.) · 2021

    First human clinical trial showing NMN (250 mg/day for 10 weeks) increases skeletal muscle insulin signaling and sensitivity in overweight/obese postmenopausal women with prediabetes.

    Early human study · PMID 33888596

  4. NAD(+) metabolism and its roles in cellular processes during ageing

    Covarrubias AJ, Perrone R, Grozio A, et al. · Nature reviews. Molecular cell biology · 2021

    Comprehensive review of NAD+ metabolism during aging, detailing how senescent cells drive NAD+ decline via CD38+ macrophage activation and outlining therapeutic restoration strategies.

    Review or meta-analysis · PMID 33353981

  5. Efficacy of Oral NMN Supplementation on Glucose and Lipid Metabolism: A Systematic Review with Meta-Analysis of RCTs

    Zhong, O., et al. · Journal of Translational Medicine · 2024

    Meta-analysis of 8 RCTs (342 adults) found NMN significantly elevates blood NAD+ levels, but short-term supplementation (250-2000 mg/d) did not show significant improvements in glucose control or lipid profile in the general population.

    Review or meta-analysis

  6. A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment

    Orr ME, Kotkowski E, Ramirez P, et al. · GeroScience · 2024

    NR was well tolerated and significantly increased blood NAD+ concentrations in older adults with MCI. Global methylation analyses indicated modest NR-associated reduction in epigenetic age by PhenoAge and GrimAge clocks.

    Controlled clinical trial · PMID 37994989

  7. Efficacy of oral nicotinamide mononucleotide supplementation on glucose and lipid metabolism for adults: a systematic review with meta-analysis on randomized controlled trials

    Zhang J, Poon ET, Wong SH · Critical reviews in food science and nutrition · 2025

    Review or meta-analysis · PMID 39116016