The coenzyme and its reputation
NAD+ deserves an examination
An essential coenzyme. An enormous reputation. The interesting part is where those two stop agreeing.
NAD+ function and human clinical findings
NAD+ is necessary for the chemistry that turns food into usable cellular energy. That is an extraordinary fact about a molecule already inside living cells. It is also a poor shortcut to deciding whether taking more of it improves health.
I distrust the jump from essential to beneficial. The 2025 review of human NAD+ precursor trials describes a field with consistent blood-test changes, inconsistent clinical results and sparse measurements inside particular tissues. A raised blood level is a real finding; a longer or healthier life is a different finding, still unproved here.
NAD Dr begins in that uncomfortable space. The heart papers contain a spectacular animal result. The NMN vs NR comparison contains much less of a contest than its name suggests. And the research page has a cancer experiment that runs against the instinct to raise NAD+ everywhere.
Coenzyme NAD+: a helper that also gets spent
NAD stands for nicotinamide adenine dinucleotide. The plus sign identifies its oxidized form; NADH is the other form in the pair that passes electrons through energy metabolism. A coenzyme is a small helper molecule for enzymes, the proteins that carry out chemical work. NAD+ is not a peptide or a protein, and vitamin B3 supplies precursors for this distinct coenzyme.
There is more to it than that reversible exchange. DNA-repair enzymes and sirtuins consume NAD+ as they work, while CD38 breaks it down. Cells must replenish the supply. Niacin and nicotinamide, forms of vitamin B3, are among the materials they can use.
This is why the familiar fuel-tank picture feels inadequate to me. NAD+ carries energy-related chemistry, gets consumed in other jobs and is rebuilt. Its importance does not establish a universal shortage, or a universal reason to add more.
An NAD supplement usually brings a precursor
An NAD+ precursor is material the body can turn into NAD+. Nicotinamide riboside, NR, becomes NMN; nicotinamide mononucleotide, NMN, then becomes NAD+ in the precursor pathways described by Covarrubias and colleagues. Intact NAD+ is poorly absorbed orally and most cells do not freely take it up whole. That is why so much of the oral research concerns NMN and NR instead.
The cleanest-looking result in this collection is the NR trial in healthy overweight adults: 100, 300 and 1000 mg/day for eight weeks raised whole-blood NAD+ by 22%, 51% and 142%, respectively. No flushing was reported, and adverse events did not differ significantly from placebo. Those amounts describe the trial groups.
That tidy rise explains the enthusiasm. It does not answer the next question: did a person gain anything that matters outside the blood sample? The comparison follows both precursors beyond that first result.
Human cardiovascular findings
The NR study in heart failure with reduced ejection fraction raised blood NAD+ and reduced some inflammatory signals in blood immune cells. The blood-pressure research in midlife and older adults reports lower systolic pressure and less arterial stiffness, with the clearest signal in those starting with above-normal pressure. Neither establishes fewer heart attacks or longer survival in people.
For a claim about heart health, my threshold is higher than an improved assay. These findings deserve follow-up precisely because heart health matters; they do not yet carry the weight of a treatment claim. The unfinished heart case puts the human results beside the mouse experiment that can so easily overshadow them.