If you have spent any time reading about NAD+ in 2026, you have probably seen a version of this claim: "a new head-to-head human trial proves NR beats NMN." You may also have seen the opposite claim — that the two precursors are interchangeable. Both are being sourced to papers published within weeks of each other this year. Only one of them was actually built to answer the question.

This post is about what those two 2026 papers really measured, why NAD+ research keeps producing confident-sounding rankings from tiny datasets, and how the Australian rules sit against the doses the trials used. For the compound basics, see our NAD+ profile.

What is NAD+, and why does everyone dose precursors instead?

Nicotinamide adenine dinucleotide (NAD+) is a coenzyme — not a peptide — that shuttles electrons in energy metabolism and acts as a substrate for enzymes including sirtuins and PARPs. It is a fragile, charged molecule, so the commercial and clinical strategy has been to feed the body precursors: nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), plain nicotinamide (Nam), or nicotinic acid.

That creates an obvious question — which precursor raises NAD+ most? Nearly a decade of trials later, the honest answer is still "it depends on what you measure, in what tissue, and for how long."

Trial one: 65 adults, and NR and NMN looked the same

In January 2026, Nature Metabolism published a randomised, open-label, placebo-controlled trial in 65 healthy adults comparing NR, NMN and nicotinamide over 14 days. Both NR and NMN increased circulating NAD+ to a comparable degree — roughly a doubling — while nicotinamide did not produce a sustained rise, only a short-lived acute bump after dosing. The authors also reported evidence that gut microbes convert NR and NMN toward nicotinic acid, and that the precursors shifted short-chain fatty acid production.

Two caveats worth stating plainly. First, the trial was open-label, not blinded. Second, several authors are employees of Nestlé Research and Nestlé Health Science, which sells NAD+ precursor products — that does not invalidate the data, but the funding and affiliation statements are worth reading before you treat it as neutral arbitration.

Trial two: six people, an MRI scanner, and no ranking

Twelve days later, iScience published the NAD-brain study from Haukeland University Hospital in Bergen, Norway. This is the paper most often cited as the "head-to-head that settles it." It is not that study.

NAD-brain was a phase I, single-centre, open-label pharmacokinetic trial: six healthy volunteers plus six people with Parkinson's disease, given 1,200 mg/day of oral NR or NMN (600 mg twice daily). In stage 1, the six healthy participants were followed over 19 days — eight days on treatment, then an 11-day washout. Its purpose was to map the kinetics of NAD+ augmentation in blood and brain, the latter using 31-phosphorus magnetic resonance spectroscopy (31P-MRS).

With six participants, no blinding, and no pre-specified superiority comparison, this design cannot rank one precursor above the other. Percentage differences pulled out of a six-person open-label PK study and rendered as "2.3× better" — a framing that has circulated mostly via supplement-brand blogs — are not a powered head-to-head result. State it as what it is: hypothesis-generating.

The finding that actually matters: NAD+ runs on a slow clock

What NAD-brain does contribute is timing. Blood NAD+ rose slowly and plateaued after roughly two weeks of dosing, then declined with similarly slow kinetics after stopping. Cerebral NAD+ showed no significant group-level increase up to day 8 — the point at which blood NAD+ was at its peak — and only became measurably elevated after about four weeks of treatment.

That decoupling is the most practically useful thing in either paper. Blood NAD+ is a pharmacology readout, not a tissue readout. A one- or two-week study that reports a doubling in whole blood has demonstrated absorption and systemic conversion; it has not demonstrated that the tissue you care about got there. It also means crossover trials need long washouts, and short trials may be reading the wrong end of the curve.

Myth vs evidence: what "NAD+ research" has and hasn't shown

  • Reliable: oral NR and NMN raise circulating NAD+. This is replicated across multiple trials and is no longer in dispute.
  • Not established: that raising blood NAD+ translates into clinical benefit. A 2023 Science Advances review of the human NR literature concluded that clinically relevant effects have been few and that the field has tended to overstate the robustness of reported findings.
  • Genuinely positive but unconfirmed: the NICE trial (90 participants, peripheral artery disease) found NR improved six-minute walk distance by 17.6 m versus placebo over six months — a functional endpoint, not a biomarker. The authors themselves called for a larger confirmatory trial.
  • Thin: intravenous NAD+ still has very little published human evidence behind it, despite being the most heavily marketed format in wellness clinics.

Is NAD+ legal in Australia? The 500 mg line, and the dose gap

Australia's position is more specific than most overseas coverage suggests. On 10 December 2025, the TGA added oral nicotinamide mononucleotide to the Permissible Ingredients Determination — meaning it can appear in listed complementary medicines, but with conditions: adults only, a maximum of 500 mg per day, use limited to 12 weeks, and not for pregnant or lactating women. That entry is sponsor-exclusive until December 2027, so the range of compliant Australian NMN products will stay narrow in the near term.

Nicotinamide riboside chloride, nicotinamide and nicotinic acid are already permitted. NAD+, NAD and NADH themselves are not permitted ingredients for listed medicines in Australia, and the TGA has published specific guidance on making NAD/NMN representations — plus a safety alert about NAD-branded products sold locally. Internationally, the FDA reversed its earlier position excluding NMN from the supplement category in September 2025.

Here is where the science and the regulation rub together: both 2026 trials dosed at 1,000–1,200 mg/day, two to two-and-a-half times Australia's permitted daily maximum. Nothing in the TGA cap is a claim about efficacy — it is a low-risk-use threshold — but it does mean the doses most often studied are not the doses a compliant Australian listed product can deliver. And a 12-week ceiling sits awkwardly beside a compound whose brain levels appeared to need about four weeks just to move.

How to read the next NAD+ headline

Three questions cut through most of it. How many participants? Was the outcome a blood biomarker or something a person can feel or do? And was the trial designed to compare precursors, or has a comparison been retro-fitted to a pharmacokinetic study? Applied to 2026's two big papers, the answers are: 65 and blood-only; six and never designed to rank.

Browse the rest of our peptide and compound profiles, or join the free updates list for plain-English summaries of new NAD+ and peptide research as it publishes.

FAQ

Is NMN legal in Australia?

Yes, with conditions. The TGA added oral NMN to the Permissible Ingredients Determination on 10 December 2025 for adults only, at a maximum of 500 mg per day for up to 12 weeks, and that entry is sponsor-exclusive until December 2027.

Is NR better than NMN?

The best-powered 2026 comparison — a 65-person trial in Nature Metabolism — found NR and NMN raised circulating NAD+ comparably over 14 days. Claims that NR clearly beats NMN largely trace to a six-person open-label pharmacokinetic study that was not designed to rank them.

Does oral NMN or NR actually raise NAD+ in the brain?

The 2026 NAD-brain study measured cerebral NAD+ by 31P-MRS and saw no significant group-level rise by day 8, with a measurable increase only after about four weeks of dosing — so blood levels and brain levels move on different timelines. It was a phase I study in 12 people.

Is IV NAD+ supported by evidence?

Not yet in any meaningful way. Intravenous NAD+ has very little published human trial evidence, and NAD+, NAD and NADH are not permitted ingredients in listed medicines in Australia.

Sources

Not medical advice. retatrutide.net.au is independent and has no commercial relationship with any supplier. NAD+ is a coenzyme, not a peptide; oral NMN is a permitted listed-medicine ingredient in Australia under strict conditions, while NAD+, NAD and NADH are not permitted ingredients, and intravenous NAD+ is not an approved therapy here.