Peptides & GLP-1 · Explainer
NAD+, NMN and NR: What the Human Evidence Actually Shows
The mechanism is real and genuinely interesting. The human outcome data is thinner than the marketing, and one of these was pulled from the US supplement market.
By Julien Malet, · Updated 2026-09-06
NAD+ is one of the most compelling stories in longevity science and one of the least settled. It is worth understanding precisely, because the gap between "this molecule matters" and "this supplement will help you" is where all the money is being made.
What NAD+ does
Nicotinamide adenine dinucleotide is a coenzyme present in every cell of your body. It is essential to energy metabolism — it shuttles electrons in the reactions that turn food into ATP — and it is a required substrate for enzymes involved in DNA repair and cellular signalling, including the sirtuins and PARPs.
NAD+ levels decline with age. That observation is well replicated across tissues, and it is the entire foundation of the category. If a molecule central to energy metabolism and DNA repair falls as you get older, raising it back sounds obviously worth doing.
Why you cannot just take NAD+
Swallowed NAD+ is broken down in the gut before it does anything useful. So the supplements are precursors — molecules your body converts into NAD+ further along the pathway:
- NR (nicotinamide riboside), sold as Niagen
- NMN (nicotinamide mononucleotide)
- Niacin and nicotinamide, the plain, cheap B3 vitamers
What human trials have established
Here the picture narrows sharply.
Raising blood NAD+ works. Multiple placebo-controlled human trials show that oral NR and NMN reliably increase NAD+ levels in blood. This part is not in dispute.
Translating that into outcomes has not. Trials have been mostly small, short, and focused on biomarkers rather than things you would notice. Results on insulin sensitivity, muscle function, aerobic capacity and inflammation have been mixed to null. A well-conducted trial in older men found NR raised NAD+ substantially without improving muscle function or metabolic health. Some trials find something; the pattern across them does not yet support the claims on the bottles.
Safety in trials to date has generally been good at the doses studied, which is a real point in the category's favour.
The honest summary: these supplements do the pharmacological thing they claim to do, and nobody has yet shown that doing it makes you healthier.
The NMN regulatory problem
In 2022 the FDA concluded NMN cannot lawfully be sold as a dietary supplement in the US, because it had been investigated as a new drug. Enforcement has been uneven and NMN is still widely available, but its legal status as a supplement is not settled — which is worth knowing before you build a long-term regimen on it.
NR does not have this problem and is sold as a supplement with FDA notification.
What about IV NAD+ and injections
IV NAD+ drips are sold at clinics for several hundred dollars a session. They bypass the digestive problem, and there is essentially no controlled outcome evidence supporting them for healthy people. Reported flushing, nausea and chest tightness during infusion are common. Injectable NAD+ sold through grey-market channels carries the sterility and identity problems described in peptide safety and sourcing.
If you want to try it anyway
That is a defensible position — the safety data looks reasonable and the mechanism is real. If you do:
- Use NR rather than NMN, for the regulatory reason above.
- Doses in trials mostly run 250–1,000 mg daily.
- Apply the usual label checks — this category has expensive proprietary blends where the NR is a minor ingredient.
- Measure something. If you cannot name what you expect to change, you will not be able to tell whether it did. Start with the basics.
And know what you are buying: a plausible mechanism, confirmed pharmacology, and unproven outcomes. That is a bet, not a treatment.