What did @biohackedhealth actually say?
The creator made three main claims: NAD levels drop to roughly half by age 50, fasting raises NAD levels in both yeast and humans, and that boost makes sirtuins "young again" which then preserves the epigenome and improves DNA repair. He also acknowledged that drinking NAD directly doesn't work well, which is actually the most accurate thing he said.
These are real scientific concepts, not invented ones. NAD+ decline with age is well-documented, and sirtuins are a legitimate area of longevity research. The problem isn't that he made things up. The problem is that he compressed a genuinely complicated, still-unresolved field into a tidy cause-and-effect story that the data doesn't fully support yet. The jump from "fasting raises NAD in yeast" to "fasting makes your sirtuins young again" is doing a lot of heavy lifting over some very thin human evidence.
Does the science back this up?
Partially, but not as cleanly as the video implies. The NAD+ decline with age is real and reasonably well-established. The fasting-to-NAD connection has animal support, but human data is thinner than his confident framing suggests.
Yoshino et al. (2018, Cell Metabolism) showed that NAD+ levels decline significantly in skeletal muscle and other tissues with age. That part checks out. On fasting, Cantó et al. (2010, Cell) demonstrated that fasting activates AMPK, which increases NAD+ biosynthesis and SIRT1 activity in mice. Translating that to humans is where it gets murkier. A 2020 paper by de Guia et al. in Science Advances showed short-term fasting increased NAD+ metabolism markers in human skeletal muscle, which is supportive but not the same as saying "NAD levels go up again" to youthful levels. The sirtuin story is even more complicated. Sirtuins require NAD+ as a cofactor, so higher NAD+ does activate them, but whether that actually preserves the epigenome or meaningfully repairs DNA in aging humans at a clinically relevant scale remains an open question. Haigis and Guarente (2006, Genes and Development) laid out the mechanistic framework, but mechanism is not the same as proven human outcome.
What did they get wrong (or right)?
He got the general direction right but overstated certainty. The claim that fasting "makes the sirtuins young again, essentially" is a significant leap. Sirtuin activity is not a single switch, and restoring NAD+ doesn't simply reverse sirtuin aging biology.
He deserves credit for flagging that "you can drink NAD and not much" happens, meaning oral NAD+ has poor bioavailability. That's accurate. NAD+ is largely degraded before absorption, which is why precursors like NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) get more research attention as delivery strategies. Yoshino et al. (2021, Science) showed oral NMN supplementation did raise NAD+ levels in skeletal muscle in postmenopausal women with prediabetes, so precursor supplementation has more traction than direct oral NAD+. What he got wrong is the yeast-to-human extrapolation. He says "we fast the yeast or we fast the human" as if those are equivalent data points. They are not. Yeast studies, including foundational work by Guarente's lab, are where a lot of this framework originated, but yeast don't have the same metabolic complexity as aging humans. Presenting them as parallel evidence is misleading without qualification.
What should you actually know?
NAD+ biology and its connection to fasting is a legitimate area of aging research, but it is nowhere near a proven anti-aging intervention in humans. Here's what the current evidence actually supports.
- NAD+ does decline with age, and this is likely meaningful for cellular energy metabolism and DNA repair enzyme function.
- Fasting activates metabolic pathways, including AMPK, that can increase NAD+ biosynthesis. This is shown in animals and has some early human support.
- Sirtuins are NAD+-dependent and play roles in DNA repair and gene regulation, but calling them "young again" after a fast is not a claim the science currently supports.
- Oral NAD+ supplementation has poor bioavailability. NAD+ precursors like NR and NMN are better studied delivery routes, though long-term human outcome data is still limited.
- If you're interested in NAD+ optimization or fasting protocols for longevity, this is exactly the kind of thing worth discussing with a clinician who can look at your actual metabolic picture, not a TikTok video.
The creator is engaging with real science and doing better than most biohacking content. But confidence level and evidence level are not the same thing, and in this video they are not matched.