NMN Nicotinamide Mononucleotide

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every cell of the body, central to two of the most important processes in cellular biology: energy metabolism (oxidative phosphorylation via the electron transport chain) and DNA repair (via PARP enzymes and sirtuins). NAD+ levels decline significantly with age — by approximately 50% between early adulthood and age 60 in most tissues — and this decline is hypothesised to be a driver of several hallmarks of ageing, including reduced mitochondrial function, impaired DNA damage repair, and declining sirtuin activity.

NMN is a direct precursor to NAD+, sitting one biosynthetic step upstream. When consumed orally, NMN is absorbed in the small intestine and converted to NAD+ in tissue via the salvage pathway enzyme NMNAT. Multiple human pharmacokinetic studies have confirmed this conversion: NMN supplementation measurably raises blood NAD+ levels in humans, with effects detectable within hours of a single dose. The mechanism is therefore confirmed in human biology. What remains under investigation is whether the rise in circulating NAD+ translates into clinically meaningful outcomes — improvements in muscle function, metabolic health, cognitive performance, or longevity — at the doses used in trials to date.

For context on where NMN sits relative to other NAD+ precursors:

Twelve randomised controlled trials have assessed NMN supplementation in human participants. Most are small (n=10–48) and short (8–16 weeks). The table below represents a cross-section of the evidence, including one null result — included because honest evidence profiles present what the trials show, not just the positive findings.

The null result above is included deliberately. It uses NR rather than NMN, but the two precursors are close enough mechanistically that null results in one inform interpretation of the other. The absence of a metabolic effect in obese men at 1,000 mg/day for 12 weeks is important context when evaluating marketing claims for NAD+ precursors as metabolic interventions.

In November 2022, the US Food and Drug Administration (FDA) issued a decision concluding that NMN cannot be lawfully marketed as a dietary supplement in the United States. The FDA's reasoning was that NMN is the subject of substantial clinical investigations as a drug (IND applications exist), and the agency determined that this pre-empts NMN's classification as a dietary supplement under the Federal Food, Drug, and Cosmetic Act. This decision resulted in major US supplement retailers removing NMN products from sale.

Trial doses across the twelve RCTs range from 250 mg/day to 900 mg/day. No clinical consensus on optimal dosing has been established. The majority of positive signals emerged at 250–600 mg/day. The 1,000 mg/day dose used in some NR trials did not outperform lower doses in the available data.

NMN has been well-tolerated in all published trials. No serious adverse events attributable to NMN supplementation were reported in any of the twelve RCTs reviewed. Mild gastrointestinal symptoms (nausea, stomach discomfort) were reported occasionally at higher doses (600–900 mg/day) and resolved without intervention. No clinically significant changes in liver function tests, renal markers, complete blood count, or cardiovascular biomarkers were observed.

One safety-focused study (Irie et al., 2020, Endocrine Journal) assessed NMN at 100–500 mg/day in healthy adult men across 12 weeks and found no adverse signals in any of 30+ safety parameters measured. This is the most comprehensive safety dataset currently available for NMN in humans. Long-duration safety data beyond 16 weeks does not currently exist in peer-reviewed literature.