NMN: The NAD⁺ Precursor at the Center of the Longevity Debate

NMN: The NAD⁺ Precursor at the Center of the Longevity Debate

Nicotinamide mononucleotide (NMN) has become one of the most popular — and controversial — molecules in the longevity world. It's a direct precursor to NAD⁺, the coenzyme that powers cellular energy, DNA repair, and sirtuin signaling. But after an FDA ruling that yanked it from the supplement market in the US, and a decade of research that shows clear biological activity but unclear clinical benefits, NMN sits at the center of a fierce debate: is it a genuine anti-aging molecule, or just the best-marketed NAD⁺ precursor?

What Is NMN?

Nicotinamide mononucleotide (NMN) is a naturally occurring nucleotide derived from ribose, nicotinamide, and phosphate. It's found in trace amounts in foods like broccoli, avocado, cucumber, and edamame — but at concentrations far too low (less than 1 mg per serving) to meaningfully affect human NAD⁺ levels.

NMN's biological significance comes from its role as a direct precursor to nicotinamide adenine dinucleotide (NAD⁺), a coenzyme essential for life. NAD⁺ is required for:

• Cellular energy production: NAD⁺ shuttles electrons in the mitochondrial electron transport chain — without it, you can't convert food into ATP
• DNA repair: NAD⁺ is consumed by PARP enzymes that fix DNA damage. The more DNA damage you accumulate with age, the more NAD⁺ you burn through
• Sirtuin activation: NAD⁺ is the fuel for sirtuins — a family of "longevity proteins" (SIRT1–7) that regulate metabolism, stress resistance, and inflammation
• Cellular cleanup: NAD⁺ supports autophagy and mitophagy, the processes by which cells clear out damaged components

The problem: NAD⁺ levels decline with age — by as much as 50-80% in some tissues by old age, according to both human and animal studies. This decline correlates with nearly every hallmark of aging: mitochondrial dysfunction, epigenetic drift, senescence, and impaired DNA repair. The question NMN research tries to answer is simple: if we restore NAD⁺ levels, do we slow or reverse aspects of aging?

NMN was first studied systematically in the early 2010s by the lab of Dr. Shin-ichiro Imai at Washington University in St. Louis. His group demonstrated that NMN administration could restore NAD⁺ levels in aged mice and reverse multiple age-associated pathologies. David Sinclair's lab at Harvard has also contributed extensively to NMN and NAD⁺ biology, though Sinclair's primary focus has been on NMN's cousin molecule, nicotinamide riboside (NR).

NMN vs. NR — What's the Difference?

Both NMN and NR are NAD⁺ precursors. NR is one step smaller — it's NMN without the phosphate group. The body converts NR → NMN → NAD⁺. NMN is one enzymatic step closer to NAD⁺, but it's also larger and requires a specific transporter (Slc12a8, discovered in 2019) to enter cells. NR, being smaller, enters cells more easily but requires an extra phosphorylation step. Neither is clearly superior — both effectively raise NAD⁺ levels in human studies. The practical difference is regulatory: NR remains available as a supplement in the US, while NMN was reclassified as a drug.

How It Works: The NAD⁺ World

NMN's mechanism is elegantly simple compared to metformin or rapamycin — it's a substrate supplementation strategy. You're not inhibiting or activating a pathway; you're simply providing more of a molecule your body needs but can't make enough of with age.

NAD⁺ Biosynthesis and Salvage

Your body makes NAD⁺ through three pathways, but the dominant one is the salvage pathway: nicotinamide (a byproduct of NAD⁺ consumption) is recycled back into NMN by the enzyme NAMPT, and NMN is then converted to NAD⁺ by NMNAT enzymes. As we age, NAMPT activity declines — and NMN levels drop with it. Oral NMN bypasses this bottleneck.

The Sirtuin Connection

Once NAD⁺ levels rise, sirtuins (SIRT1–7) become more active. These NAD⁺-dependent deacetylases remove acetyl groups from key proteins, effectively "turning on" stress resistance and longevity programs:

• SIRT1: Activates PGC-1α → mitochondrial biogenesis; deacetylates FOXO → antioxidant defense; regulates circadian rhythm
• SIRT3: The mitochondrial sirtuin — activates SOD2 (superoxide dismutase) and other antioxidant enzymes
• SIRT6: Regulates DNA repair and telomere maintenance; suppresses NF-κB-driven inflammation

PARP and CD38: The NAD⁺ Consumers

NAD⁺ isn't just made — it's actively consumed. Two major consumers drive age-related NAD⁺ depletion:

• PARP enzymes: Activated by DNA damage (which accumulates with age). PARP1 can consume massive amounts of NAD⁺ — in extreme cases, depleting cellular NAD⁺ completely, leading to energy crisis and cell death
• CD38: A cell-surface enzyme that degrades NAD⁺. CD38 expression increases dramatically with age, particularly on immune cells, and is a major driver of age-related NAD⁺ decline

NMN doesn't directly block PARP or CD38 — it simply provides more substrate to outpace the consumption. However, a 2026 Nature Medicine study showed that in immune thrombocytopenia (an autoimmune condition), NMN effectively counteracted CD38-mediated NAD⁺ depletion and reprogrammed macrophages (PMID: 42056497).

The NMN Transporter (Slc12a8)

For years, there was heated debate about whether NMN could even enter cells directly. The discovery of Slc12a8 as a specific NMN transporter in 2019 (Grozio et al., PMID: 31131364) resolved this. Slc12a8 is highly expressed in the small intestine and transports NMN from the gut into circulation. Its expression increases with age — possibly a compensatory mechanism for declining NAD⁺. This discovery also explained why oral NMN works: the gut actively absorbs it.

The Evidence

🥇 Landmark Human Data

2021 — NMN Improves Muscle Insulin Sensitivity in Prediabetic Women (Yoshino et al., Science)
The most important human NMN study to date. A 10-week, randomized, placebo-controlled, double-blind trial in 25 postmenopausal women with prediabetes who were overweight or obese. NMN (250 mg/day orally) significantly increased muscle insulin sensitivity measured by hyperinsulinemic-euglycemic clamp (the gold standard), enhanced insulin signaling (AKT and mTOR phosphorylation), and upregulated genes related to muscle remodeling. This was the study that moved NMN from "promising mouse molecule" to "human-relevant intervention." Science, 2021. PMID: 33888596

2026 — Phase 1/2 Trial in Immune Thrombocytopenia (Li et al., Nature Medicine)
A single-arm, open-label trial of low-dose oral NMN (450 mg twice daily for 2 weeks) in 25 adults with steroid-refractory ITP. Key findings: well-tolerated with no dose-limiting toxicities; 20% met the primary platelet response endpoint; overall 60% had platelet counts >1.5× baseline, and 52% maintained responses through week 8. This is the first trial showing NMN can reprogram immune cell metabolism in a human disease — and it preserved humoral immunity (antibody production), unlike typical immunosuppressants. PMID: 42056497

2024 — 8-Week NMN in Middle-Aged Japanese Men (Yamaguchi et al., Endocrine Journal)
Eleven healthy men received 250 mg/day NMN for 8 weeks. NAD⁺ levels in peripheral blood mononuclear cells (PBMCs) increased over the treatment course. In participants with insulin oversecretion, NMN modestly attenuated postprandial hyperinsulinemia — a risk factor for coronary artery disease. The regimen was well-tolerated with no significant adverse events. PMID: 38191197

2026 — Meta-Analysis of Blood Pressure Effects (Zhang et al., Nutrients)
A systematic review and meta-analysis of 10 RCTs (349 participants) found NMN supplementation was associated with a statistically significant but modest reduction in diastolic blood pressure (WMD: -2.15 mmHg). Systolic BP reduction was significant only in adults aged ≥60 years (WMD: -3.94 mmHg). The authors conclude the evidence is "preliminary and suggestive." PMID: 41901064

2026 — 24-Week Retinal Safety Trial in Older Diabetics (Shiraki et al., Geriatrics & Gerontology International)
A placebo-controlled, double-blind trial: 250 mg/day NMN for 24 weeks in older type 2 diabetes patients. NMN was safe both systemically and in the eyes. The NMN group showed preserved retinal thickness (less thinning) compared to placebo in the temporal subfield, suggesting potential for mitigating age-related retinal changes. PMID: 42082179

2026 — Sublingual vs. Oral NMN Pharmacokinetics (Wakabayashi et al., Scientific Reports)
A randomized crossover trial in 14 healthy men comparing sublingual and oral NMN. Sublingual administration led to significantly higher circulating terminal metabolites (2PY and 4PY) within 60 minutes compared to oral, suggesting faster systemic delivery. No significant differences in blood NMN, NAM, or NAD⁺ between routes. Both were well-tolerated. PMID: 42304075

🥈 Animal & Preclinical Data

2016 — Mills et al.: The Key Mouse Study (Cell Metabolism)
The foundational paper: 12 months of oral NMN administration to aged wild-type C57BL/6N mice. NMN suppressed age-associated body weight gain, enhanced energy metabolism and physical activity, improved insulin sensitivity and lipid profile, and ameliorated eye function — all without toxicity. NAD⁺ levels in tissues were rapidly restored. Importantly, lifespan extension was not measured — this was a healthspan study, not a survival study. PMID: 28068222

2016 — de Picciotto et al.: Reversal of Vascular Aging (Aging Cell)
NMN supplementation in aged mice restored endothelial function (EDD to 86%, matching young levels), reduced aortic stiffness (pulse wave velocity decreased), normalized superoxide production, and restored vascular SIRT1 activity. A key mechanistic finding: NMN increased MnSOD by 50%, directly linking NAD⁺ restoration to oxidative stress reduction. PMID: 26970090

2020 — NMN + SS-31 Synergy in Aged Hearts (Whitson et al., Aging Cell)
Both NMN and the mitochondrial-targeted peptide SS-31 independently improved different aspects of cardiac function in old mice. NMN fully reversed age-related decline in systolic function at higher workloads. The combination showed synergistic effects, "rejuvenating old hearts" and best recapitulating the young state. PMID: 32779818

2025 — NMN Ameliorates Post-Cardiac Arrest Brain Injury (Kaito et al., PLOS ONE)
Systemic NMN after cardiac arrest in mice significantly increased brain NAD⁺ and ATP, improved neurological function, reduced hippocampal neuronal injury, and improved 7-day survival from 22% to 61%. SIRT3 was upregulated in the brain, suggesting mitochondrial protection as the mechanism. PMID: 41118347

2026 — NMN for Abdominal Aortic Aneurysm (Xiong et al., Experimental & Molecular Medicine)
NMN supplementation activated SIRT7 to deacetylate serum response factor, preserving vascular smooth muscle cell contractile phenotype and attenuating aneurysm progression in mice. A novel mechanism: NAD⁺ → SIRT7 → SRF. PMID: 42420530

⚠️ Mixed / Contradictory / Cautionary Evidence

The ITP Hasn't Tested NMN — No Gold-Standard Lifespan Data
Unlike rapamycin (which was tested and validated by the NIA Interventions Testing Program across three labs — the gold standard for mouse longevity), NMN has never been put through the ITP. The Mills 2016 study showed healthspan improvements but didn't measure lifespan. Without ITP data, we simply don't know if NMN extends maximum lifespan in mice the way rapamycin does.

2026 — Systematic Review: "Clinical Effectiveness Remains Inconclusive" (Gallagher et al., Ageing Research Reviews)
A PRISMA-guided systematic review of 113 studies (33 human, 80 rodent). The blunt conclusion: "NAD⁺ augmentation shows clear biological activity, but clinical effectiveness for anti-aging or wellness outcomes remains inconclusive." While oral NR and NMN consistently showed biochemical target engagement (NAD⁺ levels go up), effects on functional, metabolic, vascular outcomes were often null or endpoint-specific. PMID: 41655607

The Bioavailability Question
Oral NMN is rapidly metabolized — some is converted to nicotinamide in the gut before reaching circulation. How much NMN reaches tissues intact vs. being converted to other NAD⁺ intermediates is still debated. Some researchers argue NMN is largely converted to NR before cellular uptake; others point to the Slc12a8 transporter as evidence for direct NMN transport. The 2026 sublingual study (PMID: 42304075) showed that bypassing first-pass metabolism via sublingual delivery increases terminal metabolite production, suggesting oral NMN does lose some through gut metabolism.

NMN Is NOT FDA-Approved — and It's Not Available as a Supplement in the US
In November 2022, the FDA ruled that NMN cannot be marketed as a dietary supplement because it was first investigated as a drug (MetroBiotech, founded by David Sinclair, holds an IND for NMN as a pharmaceutical). Under the FD&C Act, a substance investigated as a drug cannot also be sold as a supplement. This effectively removed NMN from the US supplement market. It remains available as a supplement in Japan and other countries. For US consumers, the only legal NMN products would be through clinical trials or if/when FDA-approved as a drug.

The David Sinclair Conflict of Interest
It's important to acknowledge: much of the public enthusiasm for NMN stems from Dr. David Sinclair's popular book Lifespan and his prolific media presence. Sinclair's lab contributed to NAD⁺ research, and he's an inventor on NMN-related patents licensed to MetroBiotech — a company developing NMN as a prescription drug. This doesn't invalidate the science, but it does mean the loudest voice in the NMN conversation has a substantial financial stake in the outcome. Dr. Shin-ichiro Imai, who has arguably contributed more foundational NMN research than any other scientist, also holds NMN-related patents licensed to MetroBiotech and Teijin.

Dosing and Safety

What We Know

• Typical studied doses: 250–500 mg/day orally. Most RCTs used 250 mg/day; the Phase 1/2 ITP trial used 450 mg BID (900 mg total).
• Higher doses: Doses up to 1,000–1,500 mg/day are commonly used by biohackers, but these are poorly studied. Most safety data comes from 250–500 mg/day.
• Sublingual: May provide faster systemic delivery of metabolites (PMID: 42304075), but no long-term safety or efficacy data for this route.
• Morning administration: NAD⁺ levels follow a circadian rhythm. Some researchers suggest morning dosing aligns with natural NAD⁺ peaks, though this hasn't been formally tested.
• With food or without: Not well-studied; most trials administered NMN before breakfast.
• Duration of effect: NMN raises NAD⁺ levels transiently — levels return to baseline within hours after a single dose. Sustained elevation requires daily dosing.

Known Side Effects

Important Safety Notes

• Not FDA-approved for any indication — NMN is an investigational compound. In the US, it cannot legally be sold as a dietary supplement.
• Long-term safety unknown: The longest human trial to date is 24 weeks. We have no multi-year safety data in humans.
• Cancer theoretical risk: Some cancer cells have upregulated NAD⁺ metabolism and sirtuin activity. Whether NAD⁺ boosting could theoretically promote growth of pre-existing cancers is debated and unresolved. The 2026 ITP study (PMID: 42056497) did not observe any cancer signals, but that was a 2-week trial in a specific patient population.
• Neonatal safety unclear: A 2026 mouse study (PMID: 42292811) found no overt toxicity from acute NMN exposure in neonatal mice, but transcriptomic analysis revealed molecular-level stress responses. NMN should not be used during pregnancy or breastfeeding.
• Drug interactions: Limited data. Theoretical interactions with drugs affecting NAD⁺ metabolism (niacin, PARP inhibitors in cancer treatment).

🥦 Food Sources & Equivalents

The honest answer up front: ❌ You can't meaningfully get NMN from food — the amounts are far too small.

Can you get it from food?

NMN does exist in a few everyday foods — broccoli, avocado, cucumber, cabbage, edamame (young soybeans), and tomatoes — but only in trace amounts of less than 1 milligram per serving. To put that in perspective, the research doses that raise NAD⁺ levels are 250 to 1,000 mg per day.

How much food equals the research dose?

To reach even the lowest studied dose of 250 mg, you'd need to eat hundreds of servings of broccoli or avocado every single day — physically impossible. Your body does make its own NMN from vitamin B3 (niacin), so food isn't the only route, but no realistic diet comes close to supplement-level NMN.

The bottom line

❌ Supplement only. If you want NMN at research doses, food won't get you there. If you'd rather go the food route, focus on NAD⁺ precursors you CAN get from diet — the B3 vitamins — which your body uses to build NMN on its own.

Frequently Asked Questions About NMN

The Bottom Line

Our Verdict

NMN is the most frustrating compound in the longevity space. The biology is clear and compelling: NAD⁺ declines with age, restoring it should help, and NMN is a direct precursor. The mouse data is impressive — reversal of vascular aging, metabolic dysfunction, and cardiac decline, all without toxicity. And the 2021 Science paper provides genuine human validation for metabolic benefits.

But the gap between "NAD⁺ goes up" and "you'll live longer" remains vast and unbridged. Unlike rapamycin — which has ITP-validated lifespan extension in mice across multiple labs — NMN has never been subjected to the same rigorous lifespan testing. The 2026 systematic review's sobering conclusion that functional outcomes are "often null" should give enthusiasts pause.

Add the regulatory situation: in the US, NMN isn't just unapproved — it's actively blocked from the supplement market. Products labeled "NMN" sold online are legally questionable and unregulated. Japanese NMN from legitimate manufacturers (like those used in published trials) may be higher quality but harder to access.

Our best read: NMN is a plausible but unproven NAD⁺ booster. The 2021 Science paper is real, and the safety profile is excellent. If you're a postmenopausal woman with prediabetes, the evidence for NMN is surprisingly good. For everyone else — especially healthy, active individuals — the case is built on biology and mouse data, not clinical outcomes. NMN is likely more promising than NR (better human data), less proven than metformin (vastly more safety/observational data), and far less proven than rapamycin (ITP-validated lifespan extension).

If the TAME trial defines metformin's future and PEARL defines rapamycin's future, NMN's future depends on whether MetroBiotech (or another company) successfully completes large-scale phase 3 trials as a pharmaceutical. If approved, NMN could become an FDA-regulated drug for specific aging-related conditions rather than a supplement — a different trajectory entirely from what the biohacker community initially envisioned.

For now, NMN is best understood as a promising research molecule with one strong RCT, an excellent short-term safety profile, and a mountain of unanswered questions.

Sources

1. Mills et al. — Mouse Healthspan (2016): Mills KF, Yoshida S, Stein LR, et al. Long-Term Administration of Nicotinamide Mononucleotide Mitigates Age-Associated Physiological Decline in Mice. Cell Metabolism. 2016. PMID: 28068222
2. Yoshino et al. — Human Insulin Sensitivity (2021): Yoshino M, Yoshino J, Kayser BD, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021. PMID: 33888596
3. Yoshino et al. — NAD⁺ Intermediates Review (2018): Yoshino J, Baur JA, Imai SI. NAD⁺ Intermediates: The Biology and Therapeutic Potential of NMN and NR. Cell Metabolism. 2018. PMID: 29249689
4. Grozio et al. — NMN Transporter Slc12a8 (2019): Grozio A, Mills KF, Yoshino J, et al. Slc12a8 is a nicotinamide mononucleotide transporter. Nature Metabolism. 2019. PMID: 31131364
5. Imai — NAD World 3.0 (2025): Imai SI. NAD World 3.0: the importance of the NMN transporter and eNAMPT in mammalian aging and longevity control. NPJ Aging. 2025. PMID: 39870672
6. Li et al. — NMN Phase 1/2 ITP Trial (2026): Li H, Xu Y, Chen Y, et al. Low-dose oral nicotinamide mononucleotide for immune thrombocytopenia. Nature Medicine. 2026. PMID: 42056497
7. Gallagher et al. — Systematic Review (2026): Gallagher C, Emmanuel OO. NAD⁺ supplementation for anti-aging and wellness: A PRISMA-guided systematic review. Ageing Research Reviews. 2026. PMID: 41655607
8. Zhang et al. — BP Meta-Analysis (2026): Zhang M, Chen Y, Jiang N, et al. Effects of Nicotinamide Mononucleotide Supplementation on Blood Pressure. Nutrients. 2026.

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   🦠 What This Means for Your Microbiome

   NMN does not just work inside your cells. New research shows that much of NMN's benefit actually goes through your gut bacteria.

   A 2026 study published in the British Journal of Pharmacology found something remarkable: when researchers gave NMN to mice with liver damage, the NMN protected the liver — but only if the mice had an intact gut microbiome. When antibiotics wiped out the gut bacteria, NMN stopped working. The protection was completely lost. (PMID 42478338)

   Here is what NMN does for your gut:

   • Increases butyrate-producing bacteria. A study in Metabolites (2026) found that NMN boosted bacteria like Butyrivibrio and Clostridium — the same types that produce butyrate, the gut-healing short-chain fatty acid. (PMID 42188023)
   • Activates the gut-liver axis. NMN reshapes the gut microbiome, which increases bile salt hydrolase (BSH) activity. This changes bile acid signaling and activates the FXR/FGF-15 pathway, which tells your liver to produce less of its own bile acids. Less bile acid buildup means less liver stress.
   • Cooperates with bacteria during stress. A 2026 Cell Reports study showed that when the gut is inflamed, the host and gut bacteria work together to maintain NAD+ levels. The bacteria ramp up their own NAD+ production to help. (PMID 42501334)

   What this means for you: NMN's benefits — liver protection, brain protection, anti-inflammatory effects — appear to depend partly on having a healthy gut microbiome. If your gut bacteria are depleted (from antibiotics, poor diet, or illness), you may get less benefit from NMN. This is another reason to feed your gut well while taking NMN.

   → Read more about how the gut microbiome affects aging in our guide: The Microbiome Runs the Show.

   PMID: 41901064
9. Yamaguchi et al. — 8-Week Human Safety (2024): Yamaguchi S, Irie J, Mitsuishi M, et al. Safety and efficacy of long-term nicotinamide mononucleotide supplementation. Endocrine Journal. 2024. PMID: 38191197
10. de Picciotto et al. — Vascular Aging Reversal (2016): de Picciotto NE, Gano LB, Johnson LC, et al. Nicotinamide mononucleotide supplementation reverses vascular dysfunction and oxidative stress with aging in mice. Aging Cell. 2016. PMID: 26970090
11. Whitson et al. — Cardiac NMN + SS-31 (2020): Whitson JA, Bitto A, Zhang H, et al. SS-31 and NMN: Two paths to improve metabolism and function in aged hearts. Aging Cell. 2020. PMID: 32779818
12. Shiraki et al. — Retinal Safety Trial (2026): Shiraki A, Hara C, Akasaka H, et al. Effect of Nicotinamide Mononucleotide on Retinal Thickness of Older Patients With Diabetes Mellitus. Geriatrics & Gerontology International. 2026. PMID: 42082179
13. Wakabayashi et al. — Sublingual vs. Oral NMN (2026): Wakabayashi J, Higashi S, Morifuji M. Sublingual NMN administration increases early circulating terminal catabolites. Scientific Reports. 2026. PMID: 42304075
14. Cao et al. — Neonatal NMN Toxicology (2026): Cao H, Ge X, Cui M, et al. Preliminary exploration of acute limit toxicity testing for NMN in the neonatal population. Frontiers in Pharmacology. 2026. PMID: 42292811
15. Kaito et al. — Post-Cardiac Arrest Neuroprotection (2025): Kaito D, Tamura T, Suzuki S, et al. Systemic NMN administration to mitigate post-cardiac arrest brain injury in mice. PLOS ONE. 2025. PMID: 41118347
16. Kojima et al. — SLC25A51 Mitochondrial NAD Transporter (2026): Kojima D, Yaku K, Kosugi S, et al. The Mitochondrial NAD Transporter SLC25A51 in Adipocytes. Aging Cell. 2026. PMID: 42015379
17. Katayoshi et al. — Vascular Endothelial NMN Protection (2026): Katayoshi T, Nakajo T, Kitajima N, et al. NMN protects vascular endothelial cells from M1 macrophage-derived IL-1β-induced hyperpermeability. Frontiers in Cardiovascular Medicine. 2026. PMID: 42232307
18. Xu et al. — NMN Anti-Tumor Macrophage Effect (2026): Xu H, Wan MCT, Wong CCC, et al. Nicotinamide mononucleotide enhances anti-tumor effect by resetting macrophages toward the inflammatory M1-like phenotype. Molecular Therapy: Oncology. 2026. PMID: 42179971
19. Xiong et al. — NMN Aortic Aneurysm (2026): Xiong Y, Chen J, Lu W, et al. Deacetylation of SRF catalyzed by SIRT7 protects against abdominal aortic aneurysm formation. Experimental & Molecular Medicine. 2026. PMID: 42420530

Medical Disclaimer: This page provides information for educational purposes only. Nicotinamide mononucleotide (NMN) is not FDA-approved for any medical indication. In the United States, NMN cannot legally be sold as a dietary supplement. The FDA has determined NMN is excluded from the definition of a dietary supplement because it was first authorized for investigation as a new drug. All NMN products sold online in the US exist in a regulatory gray zone and their quality, purity, and contents are not verified by any regulatory agency. The information on this page does not constitute medical advice. Do not take NMN — or any supplement, drug, or compound — without consulting a qualified healthcare professional. Long-term safety data for NMN in humans does not exist. Full disclaimer →