Short answer
NAD+ research is one of the most active areas in aging science. NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every cell, essential for energy metabolism and a substrate for enzymes linked to aging research, including sirtuins and PARPs. NAD+ levels decline with age, which makes the pathway a major topic in longevity research.
What does NAD+ do?
NAD+ has two main jobs in the cell:
A review in Nature Metabolism describes NAD+ as central to cellular metabolism, with declining levels linked to age-related changes across nearly every organ system studied [1]. A landmark 2018 review in Cell Metabolism by Rajman and colleagues summarizes the in-vivo evidence for NAD+-boosting molecules and their reported effects across animal models [3].
Sirtuins, PARPs and CD38
The enzymes that consume NAD+ are where the aging hypothesis gets its traction. The sirtuins are a family of seven NAD+-dependent deacetylases (SIRT1-SIRT7) that remove acetyl groups from proteins involved in metabolism, DNA repair and mitochondrial function. Because they depend on NAD+ as a co-substrate, their activity is directly tied to NAD+ availability - when NAD+ falls, sirtuin activity is constrained [3]. This is a central idea in the NAD+ research program: restoring NAD+ may restore the activity of enzymes that decline with age.
PARPs (poly(ADP-ribose) polymerases) use NAD+ to build ADP-ribose chains on proteins as part of DNA-damage signaling. Under stress, PARP activity can rise sharply, and since each PARP reaction consumes NAD+, high PARP demand can drain the NAD+ pool. CD38, meanwhile, degrades NAD+ as part of calcium and immune signaling. The Rajman review lays out how these competing consumers and the biosynthetic supply together determine cellular NAD+ levels, and why the balance changes with age [3].
The chemistry of NAD+
NAD+ is built from two nucleotides joined through their phosphate groups: an adenine nucleotide and a nicotinamide nucleotide. It exists in two forms in the cell - the oxidized form NAD+ and the reduced form NADH - and shuttling between the two is how the molecule carries electrons in redox reactions. This redox cycle sits at the center of energy metabolism.
NAD+ is not simply recycled forever; it is also consumed as a substrate. Enzymes called sirtuins use NAD+ to remove acetyl groups from proteins, PARPs use it in DNA repair, and CD38 and other enzymes degrade it as part of signaling. Because these enzymes actually consume the molecule, NAD+ has to be continually resynthesized, and the balance between production and consumption is the core of the aging hypothesis.
Cells can make NAD+ through the de novo pathway from tryptophan or through salvage pathways that recycle nicotinamide. The intermediate molecules NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) sit on these salvage pathways and are the focus of much precursor research [4].
Why NAD+ levels fall with age
Research points to two drivers:
The result is a gradual decline in NAD+ in many tissues. This observation, repeated across organisms and labs, is why the NAD+ pathway is one of the most active areas in aging research [1][3].
What researchers study
Common research themes include:
A 2018 review in Cell Metabolism by Yoshino and colleagues focuses specifically on the two key intermediates, NMN and NR, covering their biology, their metabolic fates and the evidence for raising NAD+ in preclinical models [4]. Together with the Rajman review, these two papers form a useful starting point for anyone new to the NAD+ precursor literature.
NAD+ vs precursor molecules
| Compound | Role | Research use |
|---|---|---|
| NAD+ | The coenzyme itself | Direct NAD+ supplementation studies |
| NMN | NAD+ precursor | Raising NAD+ in cell and animal models |
| NR | NAD+ precursor | Raising NAD+ through a different uptake route |
Labs choose between them based on the question being asked: whether the experiment needs the coenzyme directly or a precursor pathway [4]. The precursor molecules are studied because NAD+ itself is large and highly polar, which has implications for how it behaves in biological systems.
The precursor debate
One of the most discussed questions in the field is whether precursors like NMN and NR meaningfully raise NAD+ in living systems and how they differ from each other. The Yoshino review lays out the biology of both molecules - their uptake routes, their metabolic fates and the enzymes that convert them into NAD+ - and notes that their behavior depends on tissue distribution and the expression of NAD+ biosynthetic enzymes [4]. This is a genuinely active area of research, with ongoing debate about which precursor is more effective in which tissue and model.
For a laboratory, the practical lesson is that NAD+, NMN and NR are different materials with different chemistries, and the choice should follow the experimental question rather than the marketing around them. A study that wants the coenzyme directly will work with NAD+ material; a study testing whether a precursor raises NAD+ will work with the precursor. The two designs answer different questions, and each has its own literature.
Reading the evidence critically
The NAD+ field illustrates how quickly an exciting idea can outpace the data. The observation that NAD+ declines with age is widely reproduced [1][3], and the case that boosting NAD+ improves outcomes in animal models is substantial. But the evidence in humans is far more limited, and reviews in the field are careful to distinguish what has been shown in preclinical models from what remains open [3][4]. The 2025 Nature Aging review on clinical strategies explicitly discusses the challenges of translating NAD+ research beyond the bench [2].
For researchers, this means reading the primary literature and noting the model for each claim. Cell and animal findings are directly relevant to a lab working with research-grade NAD+; broader claims about human health outcomes are a different subject and are not supported by the same strength of evidence.
NAD+ in the wider research landscape
NAD+ sits at the intersection of several research traditions, which is both its strength and its complication. For the metabolism community, it is a redox coenzyme at the center of energy production. For the sirtuin community, it is a co-substrate that directly influences enzyme activity [3]. For the DNA-repair community, it is a substrate for PARPs. A single molecule touching so many processes makes it an attractive research target, but it also means that an experiment must be precise about which role of NAD+ it is actually testing.
For researchers in the longevity research category, the interest is usually in the enzyme-substrate side of the story - how NAD+ availability shapes sirtuin and PARP activity as a function of age. That framing is different from a pure bioenergetics study, and choosing the right framing determines the assay, the controls and the interpretation.
Buying NAD+ for research
If your protocol needs NAD+ material, check:
Storage and handling
NAD+ is more moisture-sensitive than many peptides, so storage discipline is important:
Experimental considerations
Because NAD+ research spans redox chemistry, enzyme activity and whole-tissue outcomes, the assay drives the design. If the question is about sirtuin activity, an in-vitro sirtuin assay with NAD+ as the co-substrate is a direct readout [3]. If the question is about whether a precursor raises NAD+, the measurement is typically NAD+ content in cells or tissues before and after exposure, using enzymatic cycling assays or mass spectrometry [4]. These are different experiments with different end-points, and choosing the right one up front saves time.
Two practical cautions apply to working with NAD+ material itself. It is moisture sensitive, so storage discipline matters more than for many other materials. And because it is a coenzyme rather than a signaling peptide, the relevant quality checks - purity by HPLC, identity by mass spectrometry or enzymatic assay, and a batch-specific COA - should be confirmed before the experiment begins, alongside research-use labeling.
FAQ
FAQ
What is NAD+?
A coenzyme found in every cell, essential for energy metabolism and signaling.
Why do NAD+ levels decline with age?
Production slows and consumption by enzymes rises, so levels fall over time.
Is NAD+ for human use?
No, it is a lyophilized research powder for laboratory use only.
What is the difference between NAD+ and NMN/NR?
NMN and NR are precursors studied for raising NAD+; NAD+ is the coenzyme itself.