I quite like the chatGPT critique here (at the end).
chatGPT:
Below is a cleaned-up version of the transcript you provided, followed by a summary and critique. I have also checked the main external claims the video relies on, especially the direct-comparison human trial, the gut-microbiome conversion work, the muscle-function meta-analysis, and the long-COVID trial. (YouTube)
Tidy transcript
Video: They’re Trying to Fool You About NMN vs NR Again
Topic: NR vs NMN, NAD boosting, gut conversion to nicotinic acid, and whether any of this produces meaningful clinical benefits.
Charles Brenner is not a scammer. He is a genuine biochemist and the scientist credited with discovering nicotinamide riboside, or NR, back in 2004. He has published hundreds of papers, and when a new study came out last month showing that his supplement, NR, boosted NAD levels 2.3 times more than its main rival, NMN, he was quick to share it on X.
What he did not share, and what I want to show you today, is something buried in that same study: evidence suggesting that the whole NR-versus-NMN debate may be beside the point. That is exactly the kind of thing supplement manufacturers on both sides would rather you did not notice.
Back in 2004, Brenner was studying an obscure enzyme called NAD synthetase. He noticed something strange: when you knock out this enzyme in yeast, the yeast should die, because they should no longer be able to make NAD. But they survived. That implied there had to be an unknown pathway that nobody had discovered yet.
He soon identified that pathway: nicotinamide riboside, a molecule naturally present in milk, could be converted directly to NAD through a set of enzymes called nicotinamide riboside kinases. It was an elegant discovery, and it launched an entire industry, because NAD is essential to a wide range of cellular functions and NAD deficiency has been linked to age-related decline.
By 2007, Brenner’s lab had shown that yeast given NR divided more than 23 times instead of the usual 13. That result got the longevity field interested.
Then, in 2016, a landmark mouse study pushed the field further. It investigated an NAD precursor and reported a host of apparent age-related benefits, including enhanced energy metabolism, increased physical activity, and improved insulin sensitivity.
But that study did not use NR. It used NMN, nicotinamide mononucleotide, and one of the scientists associated with that work was David Sinclair, who also co-founded a company developing NMN-related therapeutics.
So now there were two camps:
NR, associated with Brenner and Chromadex, and
NMN, associated with Sinclair and companies developing NMN.
Both sides argued that their molecule was the better NAD precursor. Both sides had financial interests in the outcome. And for years they have fought over which form is superior.
Brenner has been blunt. In his words, “NMN doesn’t get into cells as NMN. It gets in as NR. And there’s a safe source of NR. So why are we still talking about NMN?”
Remember that statement, because what comes next changes its meaning.
The new study Brenner shared on X comes from a group in Bergen, Norway. The researchers were independent and reportedly had no ties to supplement manufacturers. They gave six healthy adults 1,200 mg per day of both NR and NMN in a crossover design, meaning each participant took both supplements at different times.
The result: NR produced a stronger rise in blood NAD, about 2.3-fold greater than NMN.
That sounds persuasive until you remember that the study only included six people.
And there is another problem: consistency. The researchers looked at how reproducible the NAD changes were from one measurement to the next in the same individuals. The responses were not very consistent, which makes it harder to be confident about the exact size of the effect.
More importantly, just two months earlier, a much larger study was published in Nature Metabolism, one of the top journals in the field. That study included 65 participants, who were randomized into one of four groups: NR, NMN, nicotinamide, or placebo.
What did that larger study find?
It found that NR and NMN both approximately doubled circulating NAD after 14 days, with no significant difference between them.
So the headline result from the small Bergen study, the one Brenner promoted, is contradicted by a larger study with more than ten times as many participants, published in a higher-impact journal.
But the really interesting part is not who “won” the NR-versus-NMN debate. The more important point is hidden elsewhere in the data.
In the Bergen study, the researchers did not only measure NAD. They also tracked a panel of NAD-related metabolites over time. One of those metabolites was nicotinic acid (NA).
After two weeks of daily supplementation, baseline levels of NA were significantly elevated in the people taking NR and NMN.
Why does that matter?
Think of NAD synthesis as a city with multiple roads leading into it. One of those roads starts from nicotinic acid, the inexpensive form of vitamin B3. NA is a marker specific to that route. If NR were being absorbed intact, entering cells directly, and then being converted straight into NAD, you would not expect to see a strong NA signal, because NA is not on that route.
But if NA rises after NR or NMN supplementation, that suggests these compounds are first being broken down and then re-entering NAD metabolism through the Preiss–Handler pathway, the pathway that uses nicotinic acid.
And this is not just one group’s finding.
In 2022, researchers at Princeton used isotope-labeled NR so they could track exactly where orally administered NR went. They found that the main route from oral NR to increased host NAD was via conversion to nicotinic acid by gut bacteria. When they gave antibiotics to deplete the gut microbiota, the NR-derived nicotinic acid signal was effectively abolished.
Back in 2023, that evidence was mostly from mice, and many people pushed back.
But since then, additional studies have supported the same basic mechanism in animals and in humans.
A 2025 study from Japan went further. It reported that even when NR or NMN was given intravenously, bypassing the gut at first, much of it was still handled through enterohepatic circulation, returning to the intestine, where gut microbes could convert it to nicotinic acid.
And the larger Nature Metabolism human study supported the same interpretation. The investigators incubated human fecal samples with NR ex vivo and observed rapid microbial conversion of NR to nicotinic acid.
So here is the core claim: when you take an expensive bottle of NMN or NR, your gut microbes may first convert much of it into nicotinic acid, a much cheaper form of vitamin B3, and then your body rebuilds NAD from there through the Preiss–Handler pathway.
That means Brenner may be right that NMN does not really reach cells as NMN. But the same logic may also apply to supplemental NR: it may not be acting primarily as a direct intact precursor either.
So the whole fight over which premium NAD precursor is “better absorbed” could be missing the point. They may both converge on much the same downstream route.
And maybe even that does not matter, because there is a more important question:
Does raising NAD actually help people in a way they can notice?
A 2025 meta-analysis pooled randomized controlled trials of NMN and NR in adults over 60. These are the people who should benefit most if age-related NAD decline is an important driver of functional decline. But the results were disappointing: there were no significant improvements in skeletal muscle index, handgrip strength, gait speed, or chair-stand performance.
Another meta-analysis found no significant improvements in fasting glucose, insulin, HbA1c, cholesterol, or triglycerides, despite confirmed increases in NAD.
You might still argue that maybe the right target population has not been studied yet. If NAD metabolism is particularly strained in disease, perhaps boosting NAD would matter there.
That idea was tested in long COVID, where fatigue, brain fog, and immune dysfunction could plausibly involve impaired energy metabolism. Researchers gave NR to about 60 patients for 20 weeks. Blood NAD rose by around 2.6- to 3.1-fold. But there was no difference from placebo in fatigue, sleep quality, anxiety, or depression.
So yes, NR and NMN reliably raise blood NAD. That part is real. But after years of trials, there is still limited evidence that these increases translate into noticeable clinical benefits in muscle, metabolism, cognition, or long-COVID symptoms.
And it is also worth remembering that NAD decline with age is not necessarily universal or inevitable. A 2022 human study found that exercise-trained older adults had muscle NAD levels similar to those seen in younger adults.
So Brenner may have been right that some of the NMN marketing is misleading. But the same more recent research suggests that gut microbes also process NR in a way that undermines the premium-marketing story around NR itself.
That is why I chose to include nicotinamide, a simple and inexpensive form of vitamin B3, in MicroVitamin. The current human evidence does not support paying large premiums to force NAD pathways upward when that does not clearly translate into functional benefits.
The bigger picture is this: the supplement industry wants people arguing over a premium form of vitamin B3 that may cost around $60 a month, while one of the strongest known ways to support NAD metabolism is regular exercise. And exercise is also one of the most powerful interventions we have for healthy aging overall.
Summary
The video makes three main arguments.
First, it says the NR vs NMN rivalry is overhyped. A small Bergen crossover study in six people reportedly found NR raised blood NAD more than NMN, but a much larger Nature Metabolism trial in 65 healthy adults found NR and NMN produced similar increases in circulating NAD, not a clear winner. (Nature)
Second, it argues that both NR and NMN may largely work indirectly through gut-microbial conversion to nicotinic acid (NA) rather than by straightforward intact uptake into tissues. That claim is broadly consistent with the Princeton/Cell Metabolism work on oral NR, the 2025 mouse work on oral and intravenous NR/NMN fate, and the ex vivo human microbiota experiments reported in the Nature Metabolism paper. (PMC)
Third, it argues that raising blood NAD has not yet translated into convincing clinical benefits in most human trials. The 2025 meta-analysis on muscle-related outcomes in older adults concluded current evidence does not support NMN/NR for preserving muscle mass or function, and a 2025 long-COVID randomized trial reported large NAD increases without clear symptom benefit over placebo. (PubMed)
What is novel in the video
The most original and effective part is not the historical recap. It is the reframing:
The speaker shifts the question from “Is NR better than NMN?” to “Are both premium precursors mostly converging on the same cheaper nicotinic-acid route anyway, and does that matter clinically?”
That is a useful framing because it combines two strands of evidence:
- comparative human NAD-raising studies, and
- mechanistic microbiome studies on precursor fate. (Nature)
The other novel move is rhetorical rather than scientific: the video uses the newer microbiome/enterohepatic-circulation literature to turn Brenner’s own anti-NMN argument back onto NR.
Critique
What the video gets right
The broad direction is reasonable.
It is fair to say that:
- NR and NMN both raise circulating NAD in humans. (Nature)
- The best current evidence does suggest that gut microbiota are an important route by which oral NR, and probably much oral NMN, contributes to host NAD metabolism via nicotinic acid. (PMC)
- Human clinical outcomes have generally been less impressive than preclinical hype, especially for muscle and metabolic endpoints. (PubMed)
Where the video overstates the case
The biggest weakness is that it moves too quickly from “an important route involves conversion to nicotinic acid” to “therefore NR and NMN are basically just expensive nicotinic acid.”
That is too strong.
The Princeton paper says the main route from oral NR to host NAD is via gut-microbiome conversion to NA, but “main route” is not the same as “only route.” The 2025 mouse work also reported that only a small portion of oral NMN/NR was directly absorbed intact, not zero. (PMC)
So the more careful conclusion is:
much of oral NR/NMN may be processed indirectly through NA, but it has not been proven that these supplements are metabolically identical to taking plain niacin in every tissue, dose, timing pattern, or clinical context.
It relies heavily on surrogate endpoints when attacking the surrogate endpoint
The speaker criticizes the industry for focusing on blood NAD, and that criticism is fair. But then the video itself leans heavily on metabolite fingerprints as proof of mechanism. That is still indirect evidence. Strong, interesting indirect evidence, but still indirect.
A stronger argument would distinguish:
- whole-blood NAD,
- plasma precursor kinetics,
- tissue NAD pools,
- and clinical outcomes.
The video compresses those layers too much.
The clinical-benefit argument is mostly fair, but too sweeping
The statement that after “20 years and dozens of trials” there is still no noticeable benefit is rhetorically strong, but it flattens a mixed literature into a near-null verdict.
That null verdict is directionally supported for many endpoints, especially broad anti-aging claims. But there are still pockets of uncertainty:
- different tissues may respond differently,
- older, frailer, metabolically stressed, or deficiency-prone populations may not behave like healthy adults,
- and some trials report biochemical or secondary effects even when primary functional endpoints are neutral. (Nature)
So the right conclusion is probably:
the current human evidence does not justify strong consumer claims for NMN/NR as general-purpose anti-aging supplements,
not
we can now conclude the entire strategy is clinically pointless in all contexts.
It underplays nicotinamide’s own trade-offs
The video implicitly suggests that cheap vitamin B3 may be all you need. But that depends on which B3 form and at what dose. Nicotinic acid can cause flushing and has dose-dependent tolerability issues. Nicotinamide avoids flushing but has different metabolic effects. So “just buy the cheap vitamin” is too simplistic as practical advice.
Possible commercial bias is present here too
The video criticizes the NR and NMN commercial camps, which is reasonable, but then uses that critique to support the inclusion of nicotinamide in the speaker’s own supplement product. That does not invalidate the argument, but it means the speaker is not a neutral observer either.
Bottom line
This is a strong, persuasive video with a solid central thesis:
The premium NR-versus-NMN debate is probably less important than marketers suggest, because both compounds may substantially converge through gut-microbial conversion to nicotinic acid, and human evidence for meaningful functional benefit remains weak.
That said, the video overstates three things:
- that NA conversion is effectively the whole story,
- that null clinical evidence is already definitive in every context,
- and that cheap B3 is therefore a fully interchangeable substitute for all practical purposes.
So I would rate it as:
Good on framing: yes
Good on mechanistic direction: mostly yes
Good on clinical skepticism: yes
Too absolute in conclusion: also yes
If you want, I can next turn this into a claim-by-claim table with columns for claim, evidence cited, accuracy, and critique.