NMNH

NMNH is the reduced form of NMN and it is the most interesting molecule in this batch, for reasons that cut in both directions.

Two groups synthesised it independently and published within weeks of each other in 2021. Both found the same headline: NMNH raises NAD higher and faster than NMN or NR in mammalian cells, and it does so through a route that is independent of both NRK and NAMPT, going straight to NMNAT. In mice, a single administration produced a rapid and sustained NAD surge in whole blood, with increases in liver, kidney, muscle, brain, brown adipose tissue and heart but not in white adipose tissue. It also reduced damage and accelerated repair in renal tubular epithelial cells after hypoxia and reoxygenation injury.

And then the other half, from the second group, in the same year. Metabolomic analysis showed NMNH inhibited glycolysis and the TCA cycle. In vitro it induced cell cycle arrest and suppressed cell growth. The mice did not lose weight, which is the only in-vivo safety readout in the abstract.

That combination, a potent NAD enhancer that simultaneously suppresses central carbon metabolism and cell proliferation, is exactly what you would want to understand thoroughly before selling it, and it is being sold. There is no human pharmacokinetic study, no human safety study and no human trial of NMNH.

The cell-growth finding also intersects with the unresolved cancer question that hangs over this entire pathway. Suppressing proliferation could be read as desirable or as a signal that the compound is doing something substantial to metabolism that nobody has characterised in a person. Both readings are currently speculation.

There is no human evidence for NMNH. No pharmacokinetic study, no safety study, no trial. That is why this page carries no human evidence section, and it is the most important fact about the compound.

What makes NMNH worth a page anyway is that it was independently synthesised and characterised by two groups in 2021, who agreed on potency and disagreed about nothing, and one of whom also ran a metabolomic analysis and found that the compound suppressed glycolysis, the TCA cycle and cell proliferation. That second half is not a hostile finding from a rival group. It is in the same paper as the potency result, from a group that clearly found the molecule interesting.

The redox argument is worth stating because it is the mechanistic reason not to treat reduced precursors as a simple upgrade. NMN and NR raise the oxidised pool. NMNH enters as the reduced species and raises NADH too. The NAD to NADH ratio is itself a regulator of glycolytic and mitochondrial flux, so a compound that moves the ratio is not neutral with respect to energy metabolism. In the one experiment that measured it, flux went down.

Anyone selling NMNH on the strength of the fold-change is quoting the first half of a paper whose second half is a list of things the compound slowed down.

Three claim types get collapsed into one in almost all consumer writing about this pathway, and keeping them apart is most of the work. A biomarker claim is that a compound raises blood NAD. That is easy to demonstrate and for several of these compounds it is simply true. A surrogate claim is that it moves something sitting between a biomarker and a symptom, such as arterial stiffness or an acylcarnitine profile. A clinical claim is that a person walks further, remembers more, gets fewer cancers or lives longer. A compound can be firmly established at the first level and have nothing at all at the third, and that is the actual position of most of the NAD pathway. There is no published human trial of any NAD precursor with a hard clinical endpoint that reported a benefit, with one exception on this list, and that exception is nicotinamide in skin cancer, which works through DNA repair in sun-damaged skin rather than through anything to do with ageing.