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Also: nicotinamide mononucleotide · β-NMN · NR · nicotinamide riboside · nicotinamide riboside chloride · NIAGEN · MIB-626
Four separate measurements, never averaged. Independent evidence counts only studies with no sponsor attached. Methodology version v2.0-2026-10 · how we grade evidence
Claimed to raise NAD⁺ to counter age-related decline, slow ageing, and improve insulin sensitivity, mitochondrial and muscle function, blood pressure, arterial stiffness and energy. The largest and longest trial is flatly null. In 40 obese men given NR for 12 weeks at twice a typical consumer dose, there was no treatment effect on insulin sensitivity (interaction P=0.71) and no effect on total body mass, lean mass, fat mass, fat percentage, visceral or subcutaneous adipose tissue, or bone mineral density; hepatic lipid content fell non-significantly (P=0.13) in a study not powered for it, and plasma triglycerides rose in the NR group (interaction P=0.013) within the reference range.
The positive results are small and carry their own caveats. A 6-week crossover in 30 adults raised peripheral blood mononuclear cell NAD⁺ by about 60% but found blood-pressure reductions of 3.9 and 2.0 mmHg that did not survive multiple-comparison correction; the frequently quoted 9 mmHg figure comes from an exploratory n=13 subgroup on which no statistical inference was made. In 25 prediabetic postmenopausal women given NMN for 10 weeks, muscle insulin sensitivity improved — the roughly 25% figure comes from press releases, not the published abstract, which reports no effect size or p-value — while muscle NAD⁺ content did not detectably change, and body fat, blood pressure, glucose, insulin, lipids, liver insulin sensitivity, liver fat and inflammatory markers were all unchanged. Those authors state it is premature to make any clinical recommendations.
Safety knowledge is limited: human exposure is confined to trials of 6, 10 and 12 weeks with 25 to 40 participants, and no long-term data exist for either compound. Reported adverse events were mild and both side-effect dropouts in one trial occurred on placebo. No hepatotoxicity signal; no upper intake level. The two compounds are not in the same regulatory position — the FDA has concluded β-NMN is excluded from the dietary supplement definition under the drug-preclusion provision, while NR is marketed as a supplement — and conflating them is a common error.
At a glance
Both are salvage-pathway precursors that raise cellular NAD⁺, the obligate co-substrate for sirtuins, PARPs and CD38, which are implicated in the metabolic effects of calorie restriction. The split between the proximal and distal mechanism is the whole story. The proximal step is confirmed: NR raised mononuclear-cell NAD⁺ by about 60% in humans. The distal step is not: the largest and longest trial found nothing on its primary metabolic outcome, and in the one positive NMN trial muscle insulin sensitivity improved **while muscle NAD⁺ did not detectably change** — so even the favourable human result does not operate through the mechanism the marketing claims.
Dated determinations, each flagged for whether it is final and whether it covers safety only. A safety review is not an efficacy finding, and most reporting in this category conflates the two.
Sold as NIAGEN by ChromaDex. The two compounds are not in the same regulatory position and conflating them is a common error. Its GRAS notice number was not verified and is not recorded. EU status for both compounds was not verified. NMN’s US regulatory exclusion means its supply chain and quality oversight are, if anything, less assured than a lawful supplement’s.
The reasoning is the DSHEA drug-preclusion provision: a substance authorised for investigation as a new drug, for which substantial clinical investigations were instituted and made public, is excluded unless it was first lawfully marketed as a supplement or food. FDA cited clinical trials of MIB-626 (Metro International Biotech) and concluded NMN was not marketed as a supplement or food beforehand, so the "race to market" exception does not apply. Sequence of letters: May 2022 acknowledgement of a SyncoZymes NDI notification, later reversed; October 2022 first drug-exclusion determination, in a letter to Inner Mongolia Kingdomway Pharmaceutical Limited; 4 November 2022 supplemental letter to SyncoZymes; January 2023 the same conclusion in response to Effepharm Ltd; 18 January 2023 response to an amended SyncoZymes/CellMark USA notification. Citizen petitions from the Alliance for Natural Health USA, the Natural Products Association and the Council for Responsible Nutrition, and litigation, were pending as of the April 2023 source read. The position as of October 2026 was not verified and this row is therefore not marked final. This is a determination about marketing status, not about safety or efficacy.
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