Almost every NAD+ product on the market is sold on a single number: how much it raises NAD+. That number is almost always measured in blood. Two studies published in early 2026 — one from a Norwegian hospital group, one from Nestlé Research — make the same uncomfortable point from different directions: whole-blood NAD+ is a convenient surrogate, not a direct read-out of what is happening in your brain, muscle or liver. This post is a look at that measurement gap, what the newest NAD+ research can and can't tell us, and where the TGA has landed on NMN and NAD+ in Australia.

If you want the compound background first, our NAD+ profile covers the basics — including the fact that NAD+ is a coenzyme, not a peptide, despite where it usually gets shelved.

What is NAD+ and why is blood the default measurement?

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme every cell uses for redox reactions and as a substrate for enzymes like sirtuins and PARPs. Tissue NAD+ declines with age in multiple animal models, which is the entire rationale for supplementing precursors — nicotinamide mononucleotide (NMN), nicotinamide riboside (NR) and plain nicotinamide (Nam).

The problem is practical. You can draw blood repeatedly and cheaply. You cannot biopsy someone's brain nine times in a day. So "NAD+ went up X%" almost always means whole blood or red cells went up X% — and the therapeutic hypothesis was never about red cells.

The NAD-brain study: blood in days, brain in weeks

The most direct attempt to close that gap was published in iScience in January 2026 by the Neuro-SysMed group in Bergen, Norway (Tzoulis, Dölle and colleagues). The NAD-brain study was a phase I, single-centre, open-label pharmacokinetic trial: six healthy participants and six people with Parkinson's disease, given 1,200 mg/day of oral NR or NMN, with blood sampling and ³¹phosphorus magnetic resonance spectroscopy (³¹P-MRS) used to estimate cerebral NAD.

Three findings matter:

  • Blood NAD rose slowly, plateauing after roughly two weeks of dosing — not hours or days — and fell with similarly slow kinetics after stopping.
  • Cerebral NAD did not measurably shift over the first eight days, despite blood NAD already climbing.
  • Cerebral NAD increased measurably only after four weeks of treatment.

So the blood and brain curves are not the same curve. A short trial that measures blood at day 7 and calls it a result is measuring a different thing to a trial that scans the brain at week four.

Why you should not over-read it

Twelve people. Open-label. No placebo arm. Two precursors split across an already tiny sample, meaning roughly three people per arm. Secondary coverage of this study has been used to argue that one precursor beats the other by a specific multiple — some of it published by companies that sell the winning precursor. A three-person arm cannot rank precursors. What this study is genuinely good for is timing: it suggests four weeks is a more realistic minimum for cerebral change than one week, and it gives future trials a dosing schedule to design around.

The Nestlé trial: some of the "NAD+ boost" may be microbial

Published in Nature Metabolism in January 2026, a Nestlé Research–led human study compared NR, NMN and nicotinamide (Nam) head to head in healthy adults. Two results stand out.

First, NR and NMN were comparable at chronically raising baseline whole-blood NAD+, while Nam produced only an acute, transient bump. Note that this directly contradicts the "one precursor is clearly superior" framing — and both studies are small, so the honest position is that the ranking is unsettled.

Second, and more interesting: using ex vivo fermentation with human microbiota, the researchers found that NR and NMN give rise to nicotinic acid (NA) and enhance microbial growth and metabolism, with circulating NAD+ elevated via the Preiss–Handler pathway, while rapidly absorbed Nam acts through the salvage pathway. In plain terms — a meaningful share of what an oral precursor does may happen in the gut, involving your microbiome, before anything resembling "cellular NAD+ repletion" occurs.

That is a mechanism finding from one industry-funded study, not a settled fact. It is unreplicated. But it reframes the marketing story: the molecule you swallow may not be the molecule doing the work.

What this means for interpreting NAD+ research claims

Three filters worth applying to any NAD+ study or product claim:

  1. Which compartment? Whole blood, red cells, PBMCs, muscle biopsy and ³¹P-MRS brain signal are not interchangeable.
  2. At what timepoint? Under the NAD-brain kinetics, blood plateaus around two weeks and brain shifts around four. Anything shorter is likely to miss the effect it is looking for.
  3. Did the outcome move, or just the biomarker? Recent NR trials illustrate the gap — a 2025 randomised controlled trial in long COVID raised NAD+ within five weeks but did not significantly improve cognition, fatigue, sleep or mood versus placebo. Raising the marker is not the same as improving the person.

For a broader view of how surrogate endpoints get over-sold across this category, see our peptides index.

NAD+ and NMN in Australia: the TGA position

Australia's regulator has, in effect, already drawn a line between "we permit the ingredient" and "we accept the claim."

  • NMN became a permitted ingredient in listed medicines on 10 December 2025, via the Therapeutic Goods (Permissible Ingredients) Determination (No. 4) 2025. The conditions are specific: oral route only, maximum 500 mg of NMN per day, and use as an active ingredient, with a TGA compositional guideline covering identity, assay range and impurity limits.
  • Market exclusivity applies until 10 December 2027 — NMN may only be used where SyncoZymes (Shanghai) Co Ltd is the sponsor, or where another sponsor has that company's authorisation. This is why the shelf is thinner than the headlines suggested.
  • NAD+ and NADH remain non-permitted ingredients for Australian listed medicines, while NR is permitted.
  • The TGA has also published guidance specifically on making NAD, NAD+, NADH or NMN representations for listed medicines, alongside a safety alert about products sold in Australia on those grounds.

Two details worth holding together. The permitted 500 mg/day oral NMN ceiling in Australia is well under the 1,200 mg/day used in the NAD-brain phase I study — so the pharmacokinetic timings above do not transfer directly to an Australian retail product. And internationally, the FDA reversed its NMN exclusion in September 2025, which is why the regulatory picture shifted quickly across 2025–26.

Separately, intravenous NAD+ — widely marketed in clinics — still has very little published human evidence behind it, and the compartment problem above applies with even less data to resolve it.

The honest summary

NAD+ precursors reliably raise a blood marker. That much is replicated. Whether that translates to tissue NAD+ repletion depends on the tissue and the timeline, and whether tissue repletion translates to a clinical benefit remains largely unproven in adequately powered trials. The 2026 studies are a step forward precisely because they stopped assuming the surrogate was the outcome.

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FAQ

Does NMN actually raise NAD+ levels in the brain?

In the 2026 NAD-brain phase I study, cerebral NAD measured by ³¹P-MRS did not shift over the first eight days of 1,200 mg/day NR or NMN, but increased measurably by four weeks. It was an open-label study of just 12 people with no placebo arm, so treat it as preliminary timing data rather than proof.

How long does it take for NMN or NR to raise NAD+?

In the same study, blood NAD rose slowly and plateaued after roughly two weeks of daily dosing, then declined slowly after stopping. Measurable brain changes appeared later, at around four weeks.

Is NMN legal in Australia?

Yes, with conditions. NMN became a permitted ingredient for listed medicines on 10 December 2025 — oral only, maximum 500 mg per day — with sponsor exclusivity to SyncoZymes until 10 December 2027. NAD+ and NADH remain non-permitted ingredients, while NR is permitted.

Is NAD+ a peptide?

No. NAD+ is a coenzyme (a dinucleotide), not a peptide. It is commonly grouped with peptides in the longevity and wellness market, but chemically it belongs to a different class entirely.

Sources

This article is independent information only and is not medical advice. NAD+ and NADH are non-permitted ingredients in Australian listed medicines; oral NMN is permitted under specific TGA conditions (500 mg/day, sponsor-exclusive until December 2027) and NR is permitted. Speak with a qualified Australian health professional before acting on anything here.