What did @doctorjarrett actually say?
The video makes three distinct claims worth separating. First, that Bryan Johnson tested NMN and NR over 90 days and found his intracellular NAD+ levels were "comparable to a 16-year-old." Second, that NMN and NR are just precursors your body has to convert. Third, and most aggressively, that NAD+ injections deliver "100% bioavailability" and "bypass digestion," which is why people feel effects "almost immediately." That last part is where the video stops reporting and starts selling.
The Bryan Johnson reference is real, broadly speaking. Johnson has publicly shared biometric data including NAD+ measurements through his Blueprint protocol and has discussed precursor supplementation. But the framing of "teenage" NAD+ levels and what that actually means for human health is where things get complicated fast.
Does the science back this up?
The precursor biology is correct. NMN and NR are not NAD+ itself. They are substrates that cells convert through enzymatic pathways, primarily via the salvage pathway. This is established biochemistry, not controversy. The question is whether that conversion is a meaningful limitation in healthy adults.
On the "teenage levels" claim: NAD+ does decline with age. That part is well-documented. Zhu et al. (2015, Cell Metabolism) showed age-related NAD+ decline in tissues. Yoshino et al. (2021, Science) demonstrated that NMN supplementation raised skeletal muscle NAD+ levels in postmenopausal women. But "comparable to a 16-year-old" is a specific, extraordinary claim. Bryan Johnson's self-reported data is n=1 biohacking, not a controlled trial. Intracellular NAD+ measurements also vary significantly by tissue, methodology, and time of day. Treating one man's lab result as generalizable evidence is a stretch.
On injection bioavailability: intravenous NAD+ does raise blood NAD+ levels rapidly. But "100% bioavailability" for any injection route requires clarification. Intramuscular and subcutaneous injections are not 100% bioavailable by definition. Only intravenous administration achieves that, and even then, how much reaches intracellular compartments where it actually functions is a separate question the video completely ignores.
What did they get wrong (or right)?
Credit where it is due: the point that NMN and NR require conversion is accurate and genuinely useful context most supplement marketing skips entirely. That is a fair and honest disclosure.
What they got wrong is the bioavailability claim. Saying NAD+ shots deliver "100% bioavailability" is imprecise at best and misleading at worst. A 2023 review by Airhart et al. (Nutrients) noted that oral NR actually achieves meaningful systemic NAD+ elevation despite the conversion step, and the clinical gap between oral and injectable routes is not as dramatic as the video implies. The claim that injections cause effects "almost immediately" is anecdotal framing dressed as pharmacokinetics.
The Bryan Johnson angle is also being used as a credibility shortcut. Johnson is a self-experimenter with significant resources, not a clinical researcher. His data is interesting but it is not evidence that a supplement will replicate the same results in a different person with different baseline NAD+ levels, genetics, or health status.
What should you actually know?
NAD+ precursor supplementation has real, peer-reviewed support for raising NAD+ levels in humans. Martens et al. (2018, Nature Communications) showed NR supplementation increased whole-blood NAD+ by roughly 60% in older adults. That is meaningful. But raising a biomarker is not the same as reversing aging or achieving "teenage" cellular function. No study has demonstrated that outcome in humans.
If you are considering any NAD+ supplementation, including injectable forms, the route of administration, dosing, and whether you are a good candidate is a clinical conversation, not something to decide based on a 60-second Instagram video referencing one person's biohacking results. Injectable NAD+ is used in clinical settings and has a real pharmacological profile, but the "bypass digestion for instant results" framing is marketing language, not a clinical recommendation.
The video ends with a call to comment for more information, which is a lead-generation tactic. That does not make the information wrong, but it is worth knowing the context in which the claims are being made.