Longevity
NMN (Nicotinamide Mononucleotide)
aka nicotinamide mononucleotide · beta-nicotinamide mononucleotide · β-NMN · nmn · nad+ booster · mib-626
Grade
A NAD+ building-block sold as an anti-ageing supplement; it genuinely raises NAD+ levels in human blood, but whether that does anything meaningful for ageing or healthspan is still unproven.
- Class
- Nucleotide; NAD+ precursor (a vitamin-B3-derived molecule, not actually a peptide)
- Evidence
- Grade C · Early / limited human data
- Sport / WADA
- NMN is not specifically named on the WADA Prohibited List as of 2026. However, because it is not an approved medicine, anti-doping bodies note it could fall within WADA's catch-all S0 category (non-approved substances), and the strict-liability principle means athletes use unregulated supplements at their own risk, including the risk of contamination. Not a banned substance by name, but not a free pass either.
- Last reviewed
- 2026-06
Grade C · Early / limited human data
Why this grade
Several small, short human RCTs exist and reliably show NMN raises blood NAD+, but downstream benefits (walking, sleep, insulin sensitivity) are modest, inconsistent, surrogate-based and measured over weeks rather than years. No human trial demonstrates it extends healthspan or lifespan, so this is early/limited human data (C), not incomplete-but-meaningful clinical-outcome data (B).
What is it?
Your cells run on a helper molecule called NAD+, a bit like a rechargeable battery that powers the chemistry that keeps cells working. As you get older, NAD+ levels drop. NMN is one of the raw materials your body uses to make NAD+, so the idea is: swallow NMN, top the battery back up, and maybe slow down some of the wear-and-tear of ageing. Studies in people do show that taking NMN raises NAD+ in the blood. The catch is that 'higher NAD+ on a blood test' isn't the same as 'living longer or feeling younger', and so far the proof that NMN actually does the second thing in humans is thin. It's been tested in mice a lot, in people only a little, and mostly for a few weeks at a time.
Think of NAD+ as the charge in your cells' batteries, which runs down with age. NMN is like buying more battery acid: lab tests confirm you really can push the charge level back up. What nobody has yet shown in people is that a topped-up battery makes the car last longer or drive better on the road — and the glossy adverts are selling you the road trip, not the bench test.
How is it meant to work?
NMN feeds the NAD+ salvage pathway. Inside cells, the enzymes NMNAT1/2/3 convert NMN into NAD+, a coenzyme required for mitochondrial energy production, DNA-repair (PARP) enzymes, and sirtuins — a family of enzymes implicated in cellular ageing and stress resistance. NAD+ declines with age, and the rationale is that supplying NMN restores it. How NMN actually gets into cells is debated: a proposed dedicated transporter (Slc12a8) was challenged by work suggesting NMN is first broken down to nicotinamide riboside outside the cell, imported, then rebuilt. Either way, the net measurable effect in humans is a rise in circulating NAD+.
What's it studied for?
Research contexts. Not proven uses, and not recommendations.
Does the human evidence stack up?
Unusually for a 'longevity' compound, NMN does have completed human RCTs — and they tell a consistent, sobering story. Across roughly a dozen small trials (typically a few dozen participants over a couple of months, taken orally), NMN reliably and dose-dependently raises blood NAD+ and is well tolerated, with no serious adverse events reported. Beyond that, benefits are modest and patchy. Yoshino et al. (Science, 2021) found improved muscle insulin sensitivity in 25 prediabetic, overweight/obese postmenopausal women — but the effect appeared without a detectable rise in muscle NAD+ content, several other metabolic markers didn't move, the trial's randomisation was later questioned, and the result hasn't been broadly replicated. Yi et al. (GeroScience, 2023), an 80-person dose-ranging trial, reported longer six-minute walking distance and better SF-36 quality-of-life scores. Other trials hint at small improvements in sleep, fatigue and arterial stiffness, though the arterial-stiffness change only trended and was not statistically significant. The honest summary: NMN does what it says on the tin biochemically (NAD+ goes up), but no human trial has shown it slows ageing, prevents age-related disease, or extends life, and the functional benefits seen so far are small, short-term and surrogate-based. The pharma-grade version, MIB-626, is being taken through formal drug trials, which is the more rigorous route.
What could go wrong?
- !The headline claim — that NMN slows ageing or extends healthy life in humans — is unproven. Raising a blood NAD+ number is not the same as living longer or better.
- !Trials are small and short (weeks, not years), so long-term safety of sustained use is genuinely unknown.
- !Supplement-grade NMN is poorly regulated; independent testing has found products that under-deliver or contain impurities, so what's in the bottle may not match the label.
- !There is a theoretical concern that boosting NAD+ could fuel existing cancers (NAD+ supports cell proliferation), though this isn't established in humans either way — it's a reason for caution, not proven harm.
- !Marketing massively outruns the evidence: dramatic mouse results are routinely presented as if they apply to people, which they have not been shown to.
Is it legal in the UK?
NMN is not a licensed medicine in the UK. Its supplement status hinges on novel food rules: NMN was not widely eaten before 15 May 1997, so it is treated as a 'novel food' requiring Food Standards Agency authorisation before legal sale as a food supplement. As of 2026 NMN is not authorised in Great Britain — it sits 'under assessment' in the FSA novel foods process, meaning it cannot lawfully be marketed as a food supplement here, even though it is sold online from overseas. (For contrast, the related precursor nicotinamide riboside chloride is FSA-authorised as a novel food.) Anything making medicinal claims would fall under MHRA medicines law. Note the regulatory turbulence: the US FDA initially excluded NMN from supplements in late 2022 because it had been authorised for investigation as a drug (MIB-626), then reversed that position in 2025 — UK and US frameworks differ, so US status doesn't make it legal to sell as a supplement here.
Key trials
- · Phase II (investigator-led RCT)· Completed
NMN in prediabetic postmenopausal women (Yoshino/Klein, Washington University)
Improved muscle insulin sensitivity; n=25; surrogate endpoints only; no muscle NAD+ rise detected.
- · Phase II· Completed
Dose-ranging NMN in healthy middle-aged adults (Yi et al.)
Low/mid/high oral dose arms over ~2 months; NAD+ rose dose-dependently, walking distance and quality-of-life scores improved.
- · Phase II· Ongoing
MIB-626 (microcrystalline NMN, Metro International Biotech) programme
Formal drug-development trials across indications incl. metabolic/muscle and kidney; the rigorous regulatory route.
Sources
- 01Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women — Yoshino M, Yoshino J, Kayser BD, et al., Science (2021)
Landmark RCT (n=25): NMN improved muscle insulin sensitivity (without a detectable rise in muscle NAD+); many endpoints unchanged; randomisation later questioned. Widely cited and debated.
- 02The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial — Yi L, Maier AB, Tao R, et al., GeroScience (2023)
80-person dose-ranging trial: dose-dependent rise in blood NAD+, longer walking distance, better SF-36 scores, good tolerability.
- 03MIB-626, an Oral Formulation of a Microcrystalline Unique Polymorph of β-Nicotinamide Mononucleotide, Increases Circulating Nicotinamide Adenine Dinucleotide and its Metabolome in Middle-Aged and Older Adults — Pencina KM, Lavu S, Dos Santos M, et al., Journals of Gerontology: Series A (2023)
Pharmaceutical-grade NMN (MIB-626) RCT confirming dose-related NAD+ elevation; the drug-development route.
- 04Nicotinamide adenine dinucleotide metabolism and arterial stiffness after long-term nicotinamide mononucleotide supplementation: a randomized, double-blind, placebo-controlled trial — Katayoshi T, Nakajo T, Tsuji-Naito K, et al., Scientific Reports (2023)
12-week RCT; serum nicotinamide rose; arterial stiffness only trended down (not statistically significant) — illustrative of modest functional effects.
- 05Slc12a8 is a nicotinamide mononucleotide transporter (and the published rebuttal questioning it) — Grozio A, et al.; rebuttal Schmidt MS & Brenner C, Nature Metabolism (2019)
The unresolved debate over how (or whether) NMN itself enters cells versus being converted to NR first.
- 06NMN regulatory status: US FDA supplement-vs-drug reversal and UK FSA novel-food assessment — Regulatory/news coverage (FDA/NPA; UK FSA novel foods catalogue), Regulatory news and FSA novel foods catalogue (2025)
Background on the contested US supplement-vs-drug status (excluded 2022, reinstated 2025) and NMN's 'under assessment' UK novel-food position.
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