NAD+ Research

NAD+ is nicotinamide adenine dinucleotide, a nucleotide coenzyme rather than a peptide ^[1]. It is a redox cofactor for enzymes involved in DNA repair, cellular metabolism and immune function, and that biochemistry is not itself evidence of clinical benefit ^[2][16].

Identity and terminology

The molecule is a dinucleotide, with nicotinamide mononucleotide joined to adenosine monophosphate through a pyrophosphate bridge ^[1]. It contains no amino acid residues, so it has no sequence, no terminus and no chain length ^[1]. The CAS string 53-84-9 resolves to PubChem CID 5892, formula C21H27N7O14P2, molecular weight 663.4 ^[1]. NADH is the reduced form, CID 439153, molecular weight 665.4, and NADP carries a third phosphate, CID 5885, molecular weight 743.4 ^[1]. Both are separate substances from the oxidized dinucleotide described here ^[1].

What is not evidence about NAD+

Nicotinamide riboside and nicotinamide mononucleotide are precursors, chemically distinct from NAD+, so a trial of either is not evidence about NAD+ ^[2][3]. Research-grade NAD+ is the intact dinucleotide rather than a precursor.

A randomized, open-label, placebo-controlled study in 65 healthy participants compared both precursors against nicotinamide over 14 days ^[2]. The two precursors raised circulating NAD+ comparably, nicotinamide did not, and only nicotinamide acutely altered the whole-blood NAD+ metabolome ^[2]. Ex vivo in whole blood, the same group found that nicotinic acid raises NAD+ while the three tested compounds do not ^[2].

Nicotinic acid itself has been tested in large randomized outcome trials. Extended-release niacin with laropiprant in 25,673 adults with vascular disease did not reduce major vascular events, and it raised serious adverse events ^[17]. Niacin added to statin therapy in 3,414 patients was stopped early for lack of efficacy ^[18].

Human evidence for NAD+ itself

The human studies of NAD+ itself located for this review all used the intravenous route ^[4][5][16].

A pharmacokinetic pilot in 11 people had three controls and no randomization ^[4]. During intravenous infusion, plasma NAD+ and its measured metabolites did not change for at least two hours ^[4]. Urinary methylnicotinamide and NAD+ rose later, while urinary nicotinamide did not rise significantly ^[4]. It was the first human study to characterize the plasma and urine fate of directly infused NAD+ ^[4]. It reported no clinical, cognitive or metabolic outcome, so it cannot support an efficacy claim ^[4].

A retrospective record review at a commercial wellness provider compared intravenous NAD+ against intravenous nicotinamide riboside, with 30 days of follow-up ^[16]. Participants given NAD+ reported moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during infusion ^[16]. Those given nicotinamide riboside reported minor tingling and mild cramping, and all symptoms resolved when infusion ended ^[16]. Liver enzymes, hsCRP, renal markers and TSH did not change in either group ^[16]. It is retrospective rather than randomized, and its metabolic results are exploratory ^[16].

The one randomized placebo-controlled trial located is single-center, in 180 adults with heart failure from ischemic cardiomyopathy ^[5]. Ejection fraction was at or below 45%, and NYHA class II to III ^[5]. Intravenous NAD+ or matching placebo was added to guideline-directed medical therapy as a short course ^[5]. The primary endpoint, change in ejection fraction at one month, favored NAD+, with absolute values of 45.44% versus 42.44% (p=0.024) ^[5].

Every clinical secondary endpoint was a non-significant trend ^[5]. Six-month major adverse cardiac and cerebrovascular events were 14.6% versus 24.7% (p=0.089), and first unplanned heart failure hospitalization was 13.5% versus 23.6% (p=0.078) ^[5]. NYHA class improvement reached p=0.088 at one month and p=0.115 at six months ^[5]. Structural measures showed no differences, and the authors call for larger multicenter trials on clinical endpoints ^[5].

The trial has not been replicated, and its primary endpoint is a surrogate imaging measure rather than a hard clinical outcome ^[5]. The between-group difference was roughly three percentage points, against baseline standard deviations of about eight to nine points ^[5]. The population was heart failure patients on medical therapy rather than healthy adults, so it says nothing about aging, energy, recovery or athletic performance ^[5].

What has never been tested

A PRISMA-guided systematic review covering January 2010 to October 2025 identified 113 eligible intervention studies, 33 of them human and 28 of those randomized ^[3]. It found no eligible outcomes trial of intravenous or intramuscular NAD+ itself for anti-aging or wellness indications ^[3]. Its search closed before the cardiomyopathy trial appeared, and that trial is a disease indication, so both statements stand together ^[3][5].

A separate critical review of intravenous longevity infusions found placebo-controlled trials scarce and underpowered or conflicting ^[14]. Few used validated aging biomarkers, and the review described intravenous longevity therapy as experimental rather than evidence-based ^[14].

The precursor trials, and why they do not transfer

Twelve weeks of nicotinamide riboside did not improve insulin sensitivity, glucose disposal, energy expenditure, lipolysis or body composition in 40 obese insulin-resistant men ^[7]. An independent group replicated that null on insulin sensitivity, mitochondrial function and cardiac energy status ^[8]. In aged human muscle, the precursor reached its target and lowered circulating inflammatory cytokines, yet mitochondrial bioenergetics did not improve ^[9].

One widely cited trial in 25 postmenopausal women with prediabetes, all overweight or obese, reported improved muscle glucose disposal after ten weeks of nicotinamide mononucleotide ^[10]. Skeletal muscle NAD+ content did not change, and body composition and muscle function were unaffected ^[10]. It has never been replicated, and its population does not generalize to men or to healthy people ^[10].

A pilot in mild cognitive impairment had safety as its primary objective, with change in MoCA as the primary outcome ^[12]. Blood NAD+ rose 2.6-fold while cognition remained stable, which is a not-demonstrated result rather than a disproven one ^[12]. Cerebral blood flow fell in the default mode network, and the authors note that significance would not have survived multiple-comparisons correction ^[12]. An exploratory analysis found a modest increase in DNA methylation and reduced epigenetic age by PhenoAge and GrimAge ^[12].

In a 28-day trial of an NMN formulation, NAD and its metabolites rose, and lipids and blood pressure fell more than placebo ^[13]. Muscle strength, fatigability, aerobic capacity and stair-climbing power did not differ between groups ^[13].

A meta-analysis of 19 randomized precursor trials found reductions in total cholesterol and triglycerides, with nothing else reaching significance ^[11]. Its GRADE quality of evidence ranged from very low to low ^[11]. The systematic review found consistent biochemical target engagement alongside heterogeneous and often null clinical results ^[3]. None of it is evidence about NAD+ ^[2][3].

Route and absorption

Isotope-tracer work in mice showed intravenous precursors reaching tissues intact, while the same agents given orally were metabolized to nicotinamide in the liver ^[6]. That work also found NAD flux to be low in skeletal muscle, but this is mouse and cell data ^[6]. Linking it to the human muscle failures crosses a species and a substance boundary, so it is an inference rather than a demonstrated connection.

For oral NAD+ itself there is no human absorption data of any kind ^[3][4]. The intravenous pilot found rapid plasma clearance, with a metabolite pattern consistent with enzymatic breakdown ^[4].

Commercial interests in the literature

The pharmacokinetic pilot was funded by a business selling intravenous NAD and run at a clinic offering the same infusions, with one author holding both roles ^[4]. The retrospective review was written by employees of the wellness company that gave the infusions ^[16]. The head-to-head precursor comparison was run largely by employees of a food and health science company ^[2]. The cognitive impairment pilot declared an author with patents and an adviser role at the material's supplier ^[12]. The NMN formulation trial tested a proprietary product from its manufacturer ^[13]. A patent-licensing interest sits behind the positive insulin-sensitivity trial ^[10]. The randomized trial of NAD+ itself reported a non-commercial cardiovascular association fund and declared no author conflicts ^[5]. The clean nulls and the independent meta-analysis have no industry ties ^[7][8][11].

Regulatory status

NAD+ holds no FDA approval ^[15]. A field-qualified query of the FDA label database returns one record, a prescription multivitamin combination listing NAD among eight substances, with no application number ^[15]. Presence in the label database means a product is marketed rather than approved, and a confirmatory Drugs@FDA query on active ingredients returns no approved application for NAD ^[15].

EU regulatory status could not be verified in this review, so no claim is made either way. NAD+ is not approved for human therapeutic use. Material supplied as NAD+ is for laboratory research only, and it is not for human consumption.

In summary

The human record for NAD+ itself, as located for this review, runs to a randomized trial in a cardiac disease population, a pharmacokinetic pilot and a retrospective tolerability review ^[4][5][16]. There is no controlled human evidence for any indication NAD+ is actually sold for. The much larger precursor literature concerns different substances and does not fill that gap ^[2][3].

Frequently Asked Questions

Is NAD+ a peptide?

No, it is a nucleotide coenzyme, specifically a dinucleotide, and it contains no amino acid residues ^[1]. It therefore has no sequence, no terminus and no chain length, so peptide vocabulary is categorically wrong for it ^[1].

Do nicotinamide riboside and NMN trials tell us anything about NAD+?

No, because both are precursors and are chemically distinct substances from NAD+ ^[2][3]. A head-to-head human study found that NAD-related substances behave differently from one another ^[2]. A trial of a precursor is therefore not evidence about NAD+.

What controlled human evidence exists for NAD+ itself?

One randomized placebo-controlled trial in 180 adults with heart failure from ischemic cardiomyopathy met its primary endpoint, change in ejection fraction at one month ^[5]. Every clinical secondary endpoint was a non-significant trend, and the trial was single-center and has not been replicated ^[5]. A systematic review separately found no outcomes trial of NAD+ itself for anti-aging or wellness indications ^[3]. There is no controlled human evidence for any indication NAD+ is sold for.

Is anything known about oral NAD+ absorption in humans?

No human absorption data exists for oral NAD+ ^[3][4]. The mouse tracer work on oral metabolism concerns precursors rather than NAD+ itself ^[6]. The human studies located for this review all used the intravenous route ^[4][5][16].

References

1. 1

   PubChem Compound records, NCBI (PUG-REST). NAD+ CID 5892, CAS 53-84-9; NADH CID 439153; NADP CID 5885.
2. 2

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   Elhassan YS, et al. Cell Rep. 2019. PMID 31412242. DOI: 10.1016/j.celrep.2019.07.043.
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    Oliveira-Cruz A, et al. Horm Metab Res. 2024. PMID 39111741. DOI: 10.1055/a-2382-6829.
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    Orr ME, et al. Geroscience. 2024;46(1):665-682. PMID 37994989. DOI: 10.1007/s11357-023-00999-9. NCT02942888.
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    Pencina KM, et al. J Clin Endocrinol Metab. 2023;108(8):1968-1980. PMID 36740954. DOI: 10.1210/clinem/dgad027.
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    Godic A, et al. Acta Dermatovenerol Alp Pannonica Adriat. 2026;35(1):39-43. PMID 41915584. No DOI assigned by the journal.
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    US FDA, openFDA drug/label and drug/drugsfda endpoints. Snapshot last updated 2026-08-26.
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    Reyna K, et al. Front Aging. 2026;7:1652582. PMID 41704678. DOI: 10.3389/fragi.2026.1652582.
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    HPS2-THRIVE Collaborative Group. N Engl J Med. 2014;371(3):203-212. PMID 25014686. DOI: 10.1056/NEJMoa1300955. NCT00461630.
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    AIM-HIGH Investigators. N Engl J Med. 2011;365(24):2255-2267. PMID 22085343. DOI: 10.1056/NEJMoa1107579. NCT00120289.