NAD+ & NMN for Energy and Mitochondrial Function

Energy and Mitochondria — scientific infographic poster

NAD+ is the universal electron carrier without which the mitochondrial electron transport chain cannot operate. When NAD+ falls, ATP production falls with it, reactive oxygen species leak from the chain, and cells lose the energy they need for repair, signaling, and resilience. These findings come mainly from cell and animal studies, and they are why NAD+ repletion is studied in fatigue states — chronic fatigue syndrome, long-COVID, post-viral fatigue, mitochondrial myopathies, age-related sarcopenia, and the everyday fatigue of midlife. In people, the muscle data so far do not show a mitochondrial effect. This deep-dive walks through NAD+ as electron carrier, the NAD+/NADH ratio as a bioenergetic readout, the mitochondrial unfolded protein response, AMPK and sirtuin cross-talk, the published exercise-capacity trials, what is known about IV NAD+ infusions, and the doses used in trials.


Table of Contents

  1. NAD+ as Universal Electron Carrier
  2. The NAD+/NADH Ratio as Bioenergetic Indicator
  3. Mitochondrial Biogenesis via PGC-1α
  4. The Mitochondrial Unfolded Protein Response (UPRmt)
  5. AMPK and Sirtuin Cross-Talk
  6. Exercise Capacity Trials
  7. Chronic Fatigue Syndrome and Mitochondrial Dysfunction
  8. Long COVID and Post-Viral Fatigue
  9. IV NAD+ Infusions
  10. Sarcopenia and Aging Muscle
  11. Cardiac Energetics
  12. Doses Used in Trials
  13. Safety Findings and Open Questions
  14. Key Research Papers
  15. Connections
  16. Featured Videos

NAD+ as Universal Electron Carrier

Cellular energy production reduces to a single chemical operation: capturing electrons from food molecules and using their movement down an energy gradient to drive ATP synthesis. NAD+ is the molecule that does the capturing. During glycolysis, the citric acid cycle, and fatty acid β-oxidation, NAD+ accepts electrons (and a proton) from carbon-bearing substrates to become NADH. The NADH then carries those electrons to Complex I of the mitochondrial electron transport chain, where they are passed down through Complexes I, III, and IV while pumping protons across the inner mitochondrial membrane. The proton gradient drives ATP synthase, and ATP is produced.

The arithmetic of the system explains why NAD+ is so central:

Without enough NAD+, glycolysis stalls (no acceptor for the GAPDH-generated electrons), pyruvate cannot be oxidized to acetyl-CoA, the citric acid cycle slows, and cellular ATP production collapses. The cell then resorts to anaerobic glycolysis (lactate production), which yields only 2 ATP per glucose instead of ~36, and acidifies the cytoplasm.

This is why NAD+ depletion is so consequential: it does not just dial down one pathway but disables the entire oxidative metabolic apparatus on which cells depend for sustained energy production.

Back to Table of Contents

The NAD+/NADH Ratio as Bioenergetic Indicator

The cell does not just care about the absolute amount of NAD+ — it cares about the ratio of NAD+ to NADH. This ratio is the bioenergetic readout that triggers downstream signaling. A high NAD+/NADH ratio (more oxidized form) signals fasting, exercise, caloric restriction, and metabolic stress; a low NAD+/NADH ratio (more reduced form) signals fed state, abundant fuel availability, and storage mode.

The NAD+/NADH ratio influences cellular function through:

NMN/NR supplementation raises the NAD+ pool in blood, and researchers propose that it raises the NAD+/NADH ratio in tissues as well. This is the biochemical basis for describing NMN as a fasting mimetic or exercise mimetic, a framing that human trials have not borne out so far (see the exercise section).

Back to Table of Contents

Mitochondrial Biogenesis via PGC-1α

Beyond serving as electron carrier, NAD+ regulates the number and quality of mitochondria in each cell through the PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) pathway. PGC-1α is the master regulator of mitochondrial biogenesis — the cellular program for assembling new mitochondria from scratch.

The pathway works as follows:

  1. Caloric restriction, exercise, or other energy stress raises the cellular NAD+/NADH ratio.
  2. Elevated NAD+ activates SIRT1.
  3. Activated SIRT1 deacetylates PGC-1α, converting it from an inactive to an active state.
  4. Active PGC-1α drives transcription of nuclear-encoded mitochondrial genes (mitochondrial transcription factor A, respiratory chain subunits, fatty acid oxidation enzymes).
  5. New mitochondria are assembled, increasing cellular oxidative capacity.

This is the molecular basis of one of the foundational principles of exercise physiology: aerobic training increases mitochondrial density in skeletal muscle, which then enables greater endurance capacity. Researchers propose that NAD+ availability limits the SIRT1 deacetylation step. In mice, 12 months of NMN enhanced mitochondrial oxidative metabolism in skeletal muscle (Mills and colleagues, 2016). In people the result has been different: in a 2026 crossover trial in 11 untrained young men, NMN at 1,200 mg a day for 7 days abolished the exercise-induced rise in muscle mitochondrial content (Yang and colleagues, 2026).

AMPK provides a parallel pathway: AMPK phosphorylates PGC-1α at sites that prime it for SIRT1-mediated deacetylation. NAD+ and AMPK therefore cooperate to drive mitochondrial biogenesis (see the AMPK section below).

Back to Table of Contents

The Mitochondrial Unfolded Protein Response (UPRmt)

Mitochondria have their own quality-control system that monitors the folding state of their proteins and triggers a stress response when too many are misfolded. This system, called the mitochondrial unfolded protein response (UPRmt), is the mitochondrial equivalent of the better-known endoplasmic reticulum UPR.

The UPRmt was first characterized in C. elegans, where mild activation of the response extends lifespan substantially. Subsequent work in mammals has shown that the UPRmt is regulated in part by NAD+/sirtuin signaling and that it activates a coordinated program including:

Worm and mouse studies report that mitonuclear protein imbalance triggers the UPRmt and is associated with longer life in worms (Houtkooper and colleagues, 2013), and NAD+ precursors have been reported to activate the UPRmt in animal studies. The UPRmt is therefore one of the proposed mechanisms for NAD+ precursor effects in preclinical models. Mouse lifespan results with NAD+ precursors are mixed: NR extended lifespan in one study (Zhang and colleagues, 2016) but not in the multi-site Interventions Testing Program (Harrison and colleagues, 2021), and the only NMN lifespan data are a not-yet-peer-reviewed preprint (Kane and colleagues, preprint).

Back to Table of Contents

AMPK and Sirtuin Cross-Talk

AMPK (AMP-activated protein kinase) and the sirtuins are the cell's two principal energy-status sensors, and they cooperate extensively. AMPK is activated when the AMP/ATP ratio rises (signaling low energy); sirtuins are activated when the NAD+/NADH ratio rises (signaling oxidative metabolic stress).

The cross-talk runs in both directions:

In this model, interventions that activate either pathway tend to amplify the other: caloric restriction, exercise, metformin (an AMPK activator), berberine (also AMPK), and NMN/NR (sirtuin substrate) are proposed to converge on the same downstream metabolic adaptation. Some integrative practitioners combine NMN with metformin or berberine on this rationale; the combinations have not been tested in published human trials found for this page.

Exercise activates the whole system: an aerobic exercise session raises AMPK, raises the NAD+/NADH ratio, activates sirtuins, and triggers PGC-1α-driven mitochondrial biogenesis. In a cross-sectional study, muscle NAD+ in exercise-trained older people was closer to young levels than in sedentary older people (Janssens and colleagues, 2022).

Back to Table of Contents

Exercise Capacity Trials

The largest human exercise trial of NMN is Liao and colleagues (2021), a 6-week randomized, double-blind, placebo-controlled trial in 48 young and middle-aged recreational runners (ten men and two women per group). Participants received placebo, 300 mg, 600 mg, or 1,200 mg NMN per day while training 5–6 times a week.

Results:

The authors attributed the pattern to better oxygen use by skeletal muscle during submaximal exercise rather than greater peak capacity.

Other exercise and physical-function results are mixed:

Taken together, the exercise evidence consists of a few small trials with mixed findings; none tested competitive performance.

Back to Table of Contents

Chronic Fatigue Syndrome and Mitochondrial Dysfunction

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is the prototypical chronic fatigue disorder — a complex, multisystem illness characterized by post-exertional malaise, unrefreshing sleep, cognitive dysfunction, and severe functional impairment lasting more than six months. A consistent biological finding in ME/CFS is impaired mitochondrial function: reduced ATP production from peripheral blood mononuclear cells, increased lactate production with mild exertion, and abnormal cellular bioenergetic profiles on Seahorse XF analysis.

The mitochondrial dysfunction in ME/CFS has multiple proposed contributors:

The proposed rationale for NAD+ precursors in ME/CFS is to replenish the NAD+ pool, support the impaired bioenergetic machinery, and reduce the chronic inflammation proposed to drive ongoing NAD+ depletion. Clinical evidence is anecdotal and preliminary — no large RCT has tested NMN or NR specifically in ME/CFS — although some integrative practitioners include NMN/NR, often with CoQ10, D-ribose, magnesium, and L-carnitine, in ME/CFS protocols; those combinations have not been tested in published trials found for this page. See our Chronic Fatigue Syndrome page for the broader clinical picture.

Back to Table of Contents

Long COVID and Post-Viral Fatigue

The post-acute sequelae of viral infection — including the syndrome popularly known as long COVID and the broader category of post-viral fatigue syndromes following EBV, mononucleosis, Ross River virus, and others — share substantial overlap with ME/CFS in symptoms and proposed mechanism. Mitochondrial dysfunction, persistent low-grade immune activation, and reduced NAD+ availability have been proposed as common features across the post-viral fatigue spectrum.

Some integrative-medicine practitioners have used NMN, NR, and IV NAD+ infusions for post-viral fatigue. The proposed rationale draws on:

Controlled clinical trial evidence remains limited, and anecdotal reports are not equivalent to controlled data. The approaches with a longer record in post-viral fatigue management are activity pacing, attention to sleep, gradual rather than sudden return to exercise, and addressing comorbid conditions like POTS and MCAS.

Back to Table of Contents

IV NAD+ Infusions

Intravenous NAD+ is offered in longevity clinics, addiction treatment centers, and IV nutrient therapy practices, often as part of a multi-day course. Session lengths, doses and schedules are set by the clinics; they come from clinic practice, not from trials. Proponents say bypassing the gut gives higher blood levels than oral supplements.

What the published data show

Claims made for IV NAD+

Back to Table of Contents

Sarcopenia and Aging Muscle

Sarcopenia — the progressive loss of skeletal muscle mass, strength, and function with aging — is one of the most consequential aging-related changes, contributing to falls, fractures, disability, and mortality. Mitochondrial dysfunction is central to sarcopenia: aged skeletal muscle shows reduced mitochondrial density, impaired oxidative phosphorylation, and decreased oxidative capacity.

NAD+ repletion has been tested in aging-muscle contexts:

In sarcopenia research, resistance exercise and adequate protein intake (1.2–1.6 g/kg/day is a range often cited for older adults) have the strongest evidence. No trial found for this page has shown that adding an NAD+ precursor to resistance training preserves muscle.

Back to Table of Contents

Cardiac Energetics

The heart beats approximately 100,000 times per day and requires sustained, reliable ATP production to do so. Heart failure, whether with reduced ejection fraction (HFrEF) or preserved ejection fraction (HFpEF), is increasingly understood as a disease of cardiac energetics: the failing heart cannot meet its ATP demand because of impaired mitochondrial function.

In animal studies, cardiac NAD+ levels decline with age and decline further in heart failure. SIRT3, the mitochondrial sirtuin, is particularly important in cardiac myocytes. Preclinical studies have shown that boosting NAD+ levels with NMN or NR improves cardiac function in mouse models of:

Human data are limited and mostly exploratory. In the Martens 2018 NR trial (24 healthy middle-aged and older adults who completed a 6-week crossover), NR tended to lower systolic and diastolic blood pressure, but blood pressure was exploratory and the differences were not statistically significant after correction for multiple comparisons. In a 28-day trial in 30 overweight or obese adults aged 45 or older, body weight, diastolic blood pressure, and total and LDL cholesterol fell more with a pharmaceutical-grade NMN tablet than with placebo, while muscle strength, aerobic capacity, insulin sensitivity and liver fat did not differ; the trial was funded partly by the drug's developer and partly by NIH grants (Pencina and colleagues, 2023).

No trial has tested NMN or NR alongside standard cardiac care (statins, ACE inhibitors, beta-blockers, SGLT2 inhibitors, diet, exercise) in people with heart disease. The preclinical case is extensive (reviewed by Kane and Sinclair, 2018); the clinical-trial case is not yet established.

Back to Table of Contents

Doses Used in Trials

These are the doses tested in the trials on this page, not established effective doses; no dose of NMN or NR has been shown to produce a lasting clinical benefit.

NMN

NR

Timing

Combinations discussed

Decisions about supplements, especially for people with medical conditions or taking prescription medicines, belong with a clinician.

Back to Table of Contents

Safety Findings and Open Questions

Back to Table of Contents

Key Research Papers

  1. Liao, B., et al. (2021). Nicotinamide Mononucleotide Supplementation Enhances Aerobic Capacity in Amateur Runners: A Randomized, Double-Blind Study. Journal of the International Society of Sports Nutrition 18(1), 54. — doi:10.1186/s12970-021-00442-4
  2. Gomes, A.P., et al. (2013). Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear-Mitochondrial Communication During Aging. Cell 155(7), 1624–1638. — PubMed PMID: 24360282
  3. Mills, K.F., et al. (2016). Long-Term Administration of Nicotinamide Mononucleotide Mitigates Age-Associated Physiological Decline in Mice. Cell Metabolism 24(6), 795–806. — doi:10.1016/j.cmet.2016.09.013
  4. Yoshino, M., et al. (2021). Nicotinamide Mononucleotide Increases Muscle Insulin Sensitivity in Prediabetic Women. Science 372(6547), 1224–1229. — doi:10.1126/science.abe9985
  5. Martens, C.R., et al. (2018). Chronic Nicotinamide Riboside Supplementation Is Well-Tolerated and Elevates NAD+ in Healthy Middle-Aged and Older Adults. Nature Communications 9(1), 1286. — doi:10.1038/s41467-018-03421-7
  6. Igarashi, M., et al. (2022). Chronic Nicotinamide Mononucleotide Supplementation Elevates Blood NAD Levels and Alters Muscle Function in Healthy Older Men. NPJ Aging 8, 5. — PubMed PMID: 35927255
  7. Camacho-Pereira, J., et al. (2016). CD38 Dictates Age-Related NAD Decline and Mitochondrial Dysfunction Through a SIRT3-Dependent Mechanism. Cell Metabolism 23(6), 1127–1139. — doi:10.1016/j.cmet.2016.05.006
  8. Houtkooper, R.H., et al. (2013). Mitonuclear Protein Imbalance as a Conserved Longevity Mechanism. Nature 497(7450), 451–457. — PubMed PMID: 23698443
  9. Canto, C., et al. (2009). AMPK Regulates Energy Expenditure by Modulating NAD+ Metabolism and SIRT1 Activity. Nature 458(7241), 1056–1060. — PubMed PMID: 19262508
  10. Tomás-Loba, A., et al. (2008). Telomerase Reverse Transcriptase Delays Aging in Cancer-Resistant Mice. Cell 135, 609–622. (Editorial note: this paper concerns telomerase, not sirtuins; the earlier annotation "context for sirtuin-telomere interaction" did not match it.) — PubMed PMID: 19013273
  11. Grant, R., et al. (2019). A Pilot Study Investigating Changes in the Human Plasma and Urine NAD+ Metabolome During a 6-Hour Intravenous Infusion of NAD+. Frontiers in Aging Neuroscience 11, 257. — PubMed PMID: 31572171
  12. Bonkowski, M.S., Sinclair, D.A. (2016). Slowing Ageing by Design: The Rise of NAD+ and Sirtuin-Activating Compounds. Nature Reviews Molecular Cell Biology 17(11), 679–690. — doi:10.1038/nrm.2016.93
  13. Zhang, H., et al. (2016). NAD+ Repletion Improves Mitochondrial and Stem Cell Function and Enhances Life Span in Mice. Science 352, 1436–1443. — PubMed PMID: 27127236
  14. Kane, A.E., Sinclair, D.A. (2018). Sirtuins and NAD+ in the Development and Treatment of Metabolic and Cardiovascular Diseases. Circulation Research 123(7), 868–885. — PubMed PMID: 30355082
  15. Dollerup, O.L., et al. (2018). A Randomized Placebo-Controlled Clinical Trial of Nicotinamide Riboside in Obese Men: Safety, Insulin-Sensitivity, and Lipid-Mobilizing Effects. American Journal of Clinical Nutrition 108, 343–353. — PubMed PMID: 29992272
  16. Elhassan, Y.S., et al. (2019). Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Reports 28, 1717–1728. — PubMed PMID: 31412242
  17. Harrison, D.E., et al. (2021). 17-a-Estradiol Late in Life Extends Lifespan in Aging UM-HET3 Male Mice; Nicotinamide Riboside and Three Other Drugs Do Not Affect Lifespan in Either Sex. Aging Cell 20, e13328. — PubMed PMID: 33788371
  18. Kim, M., et al. (2022). Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults. Nutrients 14(4), 755. — PubMed PMID: 35215405
  19. Janssens, G.E., et al. (2022). Healthy Aging and Muscle Function Are Positively Associated With NAD+ Abundance in Humans. Nature Aging 2, 254–263. — PubMed PMID: 37118369
  20. Yi, L., et al. (2023). The Efficacy and Safety of β-Nicotinamide Mononucleotide (NMN) Supplementation in Healthy Middle-Aged Adults. GeroScience 45(1), 29–43. — PubMed PMID: 36482258
  21. Pencina, K.M., et al. (2023). Nicotinamide Adenine Dinucleotide Augmentation in Overweight or Obese Middle-Aged and Older Adults: A Physiologic Study. Journal of Clinical Endocrinology & Metabolism 108, 1968–1980. — PubMed PMID: 36740954
  22. Prokopidis, K., et al. (2025). The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis. Journal of Cachexia, Sarcopenia and Muscle 16, e13799. — PubMed PMID: 40275690
  23. Yang, D.L., et al. (2026). Anti-Inflammatory Effects of Nicotinamide Mononucleotide (NMN) in Human Skeletal Muscle After BFR-Exercise. Journal of the International Society of Sports Nutrition 23, 2632284. — PubMed PMID: 41705654
  24. Yang, W., et al. (2026). Safety and Metabolism-Related Outcomes of Oral Nicotinamide Mononucleotide Supplementation in Adults: A Systematic Review and Meta-Analysis. Nutrients 18(14), 2251. — PubMed PMID: 42514320
  25. Kane, A.E., et al. (2026). Long-Term NMN Treatment Increases Lifespan and Healthspan in Mice in a Sex Dependent Manner. Preprint, Research Square (earlier version posted to bioRxiv 2024); not peer-reviewed. — doi:10.21203/rs.3.rs-10913337/v1

PubMed Topic Searches

  1. PubMed: NMN exercise capacity
  2. PubMed: NAD+ ME/CFS
  3. PubMed: NAD+ long-COVID post-viral
  4. PubMed: IV NAD+ clinical
  5. PubMed: SIRT3 cardiac mitochondria
  6. PubMed: AMPK-SIRT1 mitochondrial biogenesis

Back to Table of Contents

Connections

Back to Table of Contents