NAD+ and NMN in 2026: What the Latest Research Changed

What raising NAD+ actually means

Nicotinamide adenine dinucleotide — NAD+ — is a coenzyme that sits at the center of cellular energy metabolism. Every mitochondrion uses it. Every sirtuin (the family of regulatory enzymes that includes SIRT1, the gene that launched the resveratrol craze in 2003) needs it. Every PARP enzyme (the DNA-damage repair machinery) consumes it. NAD+ levels decline with age in nearly every tissue measured, and that decline tracks with the decline in mitochondrial output, immune function, and DNA repair capacity.^[6]

That observation — NAD+ falls with age, and most of the things we care about preserving with age depend on NAD+ — is the entire foundation of the NMN supplement industry. The logic is clean: if you raise NAD+, you should slow or reverse some of the age-associated dysfunctions that NAD+ depletion is implicated in.

The first part of that logic is now settled. A 2024 systematic review of six randomized controlled trials, with NMN doses between 250 and 900 mg/day across 10 to 12 weeks, found that every trial showed a significant rise in blood NAD+ concentration with mild side-effect profiles.^[10] A 2026 PRISMA-guided systematic review covering 33 human intervention studies confirmed the same biochemical pattern: oral NR and NMN consistently engage their target.^[2] If your question is "does taking NMN raise NAD+ in my blood?" — the answer is yes.

That is also where the certainty stops.

The 2025 mechanism paper that changes the story

Until last year, the standard explanation of how oral NMN works was simple: NMN is absorbed in the small intestine, enters the bloodstream, gets shuttled into cells by a transporter called Slc12a8, and converts to NAD+ inside the cell. Clean pathway, easy to draw, easy to sell.

A 2025 Science Advances paper by Yaku and colleagues at the University of Toyama complicated that story considerably.^[3] Using isotope-labelled NMN and NR in mice, they tracked where the molecules actually go. The answer: only a small fraction of orally administered NMN or NR is directly absorbed intact. The majority sits in the gut long enough to be deamidated by the gut microbiota to nicotinic acid (NA, also known as niacin). The nicotinic acid then enters portal circulation, travels to the liver, and is preferentially used there to synthesize NAD+ through the Preiss–Handler pathway — a separate biosynthetic route from the salvage pathway most NMN marketing describes.

Even intravenously administered NMN — which should bypass the gut entirely — was rapidly degraded into nicotinamide, secreted into bile, returned to the gut, and deamidated by the same microbiota before re-entering circulation as nicotinic acid. The enterohepatic loop dominates.

Three implications follow, and they all matter:

• Your gut microbiome may be the rate-limiting factor. Two people taking the same NMN dose can have very different downstream NAD+ profiles depending on whether their microbiota has the deamidase activity to convert NMN to nicotinic acid efficiently. Antibiotic use, low-fiber diets, and dysbiosis would all be expected to blunt the response. None of the published NMN trials have stratified by microbiome composition.
• Cheap niacin may be a more direct route. If nicotinic acid is the actual bioactive intermediate that reaches the liver, then giving nicotinic acid directly skips the conversion step. A 2024 placebo-controlled trial in older inactive men found that 2 weeks of nicotinic acid (acipimox, 750 mg/day) significantly improved mitochondrial respiration and electron transport chain protein content in skeletal muscle.^[8] The effect size — measurable changes in mitochondrial function in two weeks — is striking. Acipimox costs a fraction of what equivalent NMN doses cost.
• The "tissue NAD+" story needs rewriting. Most NMN literature talks about raising NAD+ in cells across the body. The Yaku data suggests the gain is liver-concentrated, with other tissues benefitting more modestly through circulating nicotinamide. This may explain why human NMN trials have shown such heterogeneous effects on muscle, brain, and cardiovascular endpoints — those tissues are downstream of the liver hub, not direct uptake sites.

None of this means NMN doesn't work. It means it works differently than the marketing has been describing for the last five years, and the new model predicts which people are likely to respond and which aren't.

Biomarker engagement is real. Clinical outcome is what we still don't have. Confusing the first for the second is the central error of the NMN narrative.

The 2024 walking-speed RCT — and what its primary endpoint missed

Morifuji and colleagues published the most-cited NMN trial of 2024 in GeroScience: a 12-week, double-blind, placebo-controlled study of 60 older adults receiving 250 mg/day of NMN.^[4] It is worth reading carefully because the headline most people remember is "NMN improves physical function in seniors," and the underlying data is more mixed than that.

The pre-specified primary endpoint was a stepping test — a standard measure of lower-limb power and coordination. On that endpoint, NMN showed no significant difference from placebo at either 4 or 12 weeks. If the trial had been published as a regulatory-style report card on its primary outcome, it would have read as negative.

The secondary endpoints told a different story. The NMN group showed a significantly shorter 4-metre walking time at 12 weeks compared to placebo, and a significant negative correlation between the change in walking time and the change in blood NAD+ and its metabolites. Sleep quality, measured by the Pittsburgh Sleep Quality Index, improved in the NMN group — particularly the "daytime dysfunction" subscore. NAD+ levels rose as expected. No adverse effects were reported.

How to read this honestly: 250 mg of NMN over three months produced biochemical target engagement (NAD+ went up), null effect on its primary physical endpoint (stepping), and statistically significant improvement on softer secondary endpoints (walking, sleep). That is consistent with a small-to-modest effect on physical function that didn't reach the primary outcome bar but suggests biological activity. It is not consistent with the "anti-aging breakthrough" framing the supplement industry attached to the paper.

Yamaguchi and colleagues, also publishing in 2024, ran an 8-week single-arm study of 250 mg/day NMN in 11 middle-aged Japanese men and found NMN was well tolerated, raised NAD+ in peripheral blood mononuclear cells, and modestly attenuated postprandial hyperinsulinemia in the subgroup with insulin oversecretion.^[5] Useful biology. Eleven participants, no placebo control. Hypothesis-generating only.

The 2026 Nature Medicine trial — NMN's first disease win

The most interesting NMN paper of the last decade was published in Nature Medicine in April 2026 by Li and colleagues at the Chinese Academy of Medical Sciences.^[1] It is a phase 1/2, single-arm, open-label trial of low-dose oral NMN — 450 mg twice daily for two weeks — in 25 adults with steroid-refractory or steroid-dependent immune thrombocytopenia (ITP), an autoimmune disease in which the immune system destroys platelets.

The mechanistic logic is unusual. CD38 is an enzyme on macrophages that consumes NAD+. In ITP, CD38 activity depletes macrophage NAD+, which polarizes macrophages toward an inflammatory M1 phenotype and increases their expression of Fc gamma receptor I — the receptor that recognizes antibody-coated platelets and eats them. By giving NMN, the investigators hypothesized they could restore macrophage NAD+, reverse the M1 polarization, downregulate the receptor, and stop the platelet destruction. Mouse data supported the model.

The trial results: no dose-limiting toxicities, no treatment-related serious adverse events. Mild adverse events in 12 percent of patients. Five of 25 patients (20 percent) met the strict primary platelet-response endpoint (platelets above 50 × 10⁹/L within two weeks, confirmed on two consecutive measurements, without rescue therapy). In exploratory analysis, 60 percent of patients achieved platelet counts more than 1.5× their baseline during treatment, and 52 percent maintained the response through week 8. Immunoglobulin levels stayed stable — suggesting the immune reset was selective rather than the broad immunosuppression that steroids and anti-CD20 therapies cause.

Why this matters beyond ITP:

• It is the first peer-reviewed top-tier journal trial of NMN as a therapeutic — not a wellness supplement — in a defined disease population with a regulatory-style primary endpoint and an exploratory secondary structure.
• It identifies a specific cellular mechanism (CD38–NAD+ axis in macrophages) that NMN can plausibly modulate. This is a tighter, more falsifiable claim than the diffuse "anti-aging" framing of most NMN literature.
• It establishes a safety profile for 900 mg/day over two weeks in a non-healthy population. That is meaningful — if NMN at this dose causes problems, sick patients are usually where they show up first.
• It opens a door: the same CD38–NAD+ axis is upregulated in normal aging (one of the leading models of why NAD+ drops with age is increased CD38 activity in senescent cells — the same axis behind the longevity pitch for apigenin as a CD38 inhibitor). The ITP trial may turn out to be a proof of mechanism for using NMN against age-related immune dysfunction more broadly. May.

Caveats that need stating: 25 patients, single arm, no placebo, 2-week treatment, 20 percent met primary endpoint. That is a positive signal in a hard-to-treat population. It is not a confirmed efficacy result, and there is no comparison to existing thrombopoietin-receptor agonists or anti-CD20 therapy.

The 113-study systematic review — and what it says about claims

Earlier this year, Gallagher and Owoturo published a PRISMA-guided systematic review in Ageing Research Reviews covering 113 eligible studies — 33 human intervention studies (28 randomized) and 80 rodent studies — across January 2010 to October 2025.^[2] It is the most comprehensive overview of the NAD+ supplementation evidence base to date.

The summary line is worth quoting precisely: "Oral NR and NMN consistently demonstrated biochemical target engagement and were generally well tolerated over weeks to months; however, effects on functional, metabolic, vascular, and other healthspan-relevant outcomes were heterogeneous and often null or endpoint-specific."

Translate that into plain English: the supplements do what they say they do at the molecular level (raise NAD+), they are safe at the doses studied (250 to 900 mg/day for up to a year), and they do not consistently produce the clinical outcomes the marketing claims they do. Sometimes a trial shows an effect on muscle function. Sometimes another trial shows nothing. Sometimes a trial shows improvement in cognition. Sometimes another trial shows nothing. The signal is real but small, inconsistent, and endpoint-specific.

The review's recommendation is straightforward: larger, longer trials with prespecified clinically meaningful endpoints. The current evidence base is not strong enough to support broad anti-aging claims. It is also not weak enough to dismiss the precursors entirely. We are in the awkward middle.

There is one additional finding from the review worth flagging. The authors note that no eligible outcomes trial has evaluated intravenous or intramuscular NAD+ for anti-aging or wellness indications. The IV NAD+ wellness clinics that have proliferated over the last five years are operating in a complete evidence vacuum. The one nonrandomized IV NMN study they identified contributed only short-term safety and biomarker information. If anyone tells you IV NAD+ drips have evidence behind them, they are not telling you the truth.

Beyond NMN — trigonelline, niacin, and the precursor question

A 2024 paper in Nature Metabolism by Membrez and colleagues at Nestlé Research identified a new NAD+ precursor that has nothing to do with the NMN/NR family: trigonelline, a natural alkaloid found in coffee, fenugreek, and certain other plants. Serum trigonelline levels are reduced in human sarcopenia and correlate positively with muscle strength and mitochondrial function. Dietary trigonelline supplementation in mice enhanced muscle strength and prevented fatigue during ageing through an NAD+-dependent, sirtuin-mediated mechanism.^[7]

Trigonelline incorporates into the NAD+ pool through the same Preiss–Handler pathway that the Yaku paper highlighted as the dominant route for orally administered NMN and NR — which is mechanistically consistent. The animal data is encouraging. There is no published human RCT yet.

The broader picture across these papers is that the NAD+ precursor space is larger than NMN. Nicotinamide riboside (NR) has a roughly parallel evidence base to NMN with similar caveats. Nicotinic acid (niacin, in either immediate-release or extended-release form) is the cheapest option with the longest clinical history and the most direct hepatic conversion. Niacinamide (nicotinamide) is widely available and well-tolerated. Trigonelline is a research direction. Nicotinamide adenine dinucleotide hydride (NADH) and reduced forms are emerging.

From a strict cost-per-NAD-rise standpoint, niacin is almost certainly the most efficient choice for someone who just wants to raise tissue NAD+. The trade-off is the flushing side effect that niacin causes at meaningful doses, and the legitimate concern that chronic high-dose niacin has its own metabolic effects (insulin resistance, hepatic stress) that need to be weighed.

Lifespan vs healthspan — where the evidence stops

The marketing framing for NMN has consistently been about longevity — slowing aging, extending lifespan, reversing biological age. The actual evidence is about healthspan proxies, and weakly. There is no published randomized controlled trial of NMN with lifespan as the endpoint in humans. There is no published RCT of NMN with mortality, hard cardiovascular outcomes, dementia incidence, or cancer incidence as the endpoint in humans. The longest published human NMN trials are around a year. Lifespan trials in humans take decades.

What we have instead is biomarker engagement (NAD+ rises), short-term functional signals (walking, sleep, modest mitochondrial improvements), one disease-state phase 1/2 (ITP), and a large rodent literature showing healthspan and lifespan extension in mice — much of which has been difficult to replicate at the same effect size across labs.^[9]

That is not a basis to claim NMN extends human lifespan. It is also not a basis to claim it doesn't. It is a basis to say: we do not yet know, and the people selling NMN as a longevity drug are operating ahead of the data.

Practical position — what I think the data justifies right now

I have been around the longevity and peptide space for over a decade and a half, and I have watched NMN ride the full arc — from David Sinclair's mouse papers to the supplement boom to the FDA's late-2022 reclassification of NMN as an investigational new drug ingredient in the United States to where we are now. Here is what I think the post-2024 data actually justifies.

• If you are healthy and curious — 250 to 500 mg NMN/day is biologically active and apparently safe at this dose range across multiple short-to-medium-term human trials. The effect size on hard outcomes is small to undetectable. You will probably raise your NAD+. Whether that changes anything you care about in the next 20 years is unknown.
• If your goal is the cheapest route to raised tissue NAD+ — niacin is the answer the evidence supports. Acipimox and extended-release nicotinic acid have decades of clinical history, mechanistic alignment with the Yaku enterohepatic-circulation model, and a 2024 placebo-controlled signal on mitochondrial function in older men. The flushing is real. The cost is a fraction of NMN.
• If you are on chemotherapy or have an autoimmune disease — talk to your oncologist or rheumatologist before touching any NAD+ precursor. The ITP paper shows NMN can modulate macrophage behavior. The chemotherapy oocyte-protection paper shows NMN can interact with cyclophosphamide's mechanism.^[11] Both are useful in their context. Neither is something to combine with active treatment without supervision. There are also legitimate concerns about precursor effects on cancer cell metabolism that the safety literature has not fully resolved.
• Skip the IV NAD+ clinics. Zero outcomes evidence. Real costs. The 2026 systematic review is explicit about this.
• Skip the megadoses. The trials top out around 900 mg/day for limited durations. The "more is more" supplement-stacker culture is not supported by the data and the dose–response curve almost certainly plateaus — and probably reverses, given that excess nicotinamide is a methyl-donor sink that depletes SAM and methionine.

The honest position, given what 2024–2026 has added: NMN engages its target reliably, has a credible mechanism we now understand better than we did, has its first defensible disease-state signal in a top-tier journal, and still does not have the longevity outcome data the marketing has been promising for five years. The story is more interesting than it was, and more cautious. Both at once.

Biomarker engagement is real. Clinical outcome data is partial. Lifespan data does not exist. Buy the precursors that fit the model. Skip the ones that don't.

References

1. Li H, Xu Y, Chen Y, et al. Low-dose oral nicotinamide mononucleotide for immune thrombocytopenia: a phase 1/2 trial. Nature Medicine. 2026.
2. Gallagher C, Owoturo OE. NAD+ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Research Reviews. 2026;116:103057.
3. Yaku K, et al. Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD+ synthesis via enterohepatic circulation. Science Advances. 2025.
4. Morifuji M, et al. Ingestion of β-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adults in a double-blind randomized, placebo-controlled study. GeroScience. 2024.
5. Yamaguchi S, et al. Safety and efficacy of long-term nicotinamide mononucleotide supplementation on metabolism, sleep, and nicotinamide adenine dinucleotide biosynthesis in healthy, middle-aged Japanese men. Endocrine Journal. 2024.
6. Iqbal T, et al. The therapeutic perspective of NAD+ precursors in age-related diseases. Biochemical and Biophysical Research Communications. 2024.
7. Membrez M, et al. Trigonelline is an NAD+ precursor that improves muscle function during ageing and is reduced in human sarcopenia. Nature Metabolism. 2024.
8. Deane C, et al. Nicotinic acid improves mitochondrial function and associated transcriptional pathways in older inactive males. Translational Exercise Biomedicine. 2024.
9. Yang X, et al. An Updated Review on the Mechanisms, Pre-Clinical and Clinical Comparisons of NMN and NR. Food Frontiers. 2024.
10. Dewi MYA, et al. Efficacy of NMN Supplementation in Blood NAD for Anti-Aging in Adults: A Systematic Review. Journal of Advanced Research in Medical and Health Science. 2024.
11. Shen L, et al. Nicotinamide mononucleotide protects ovarian function and oocyte developmental competence during chemotherapy. Journal of Ovarian Research. 2025;18(1):193.
12. Alegre GFS, et al. NAD+ Precursors NMN and NR: Potential Dietary Contribution to Health. Current Nutrition Reports. 2023.