If you take NAD+ boosters, follow rapamycin chatter, or have read about senolytics, this may sting. A new systematic review in Frontiers in Genetics looked at which interventions actually moved next-generation epigenetic aging clocks in human trials. Nicotinamide riboside (NR), rapamycin, and senolytics showed no detectable effect. Exercise, a plant-rich diet, and a cholesterol drug did move them. So did a handful of stranger candidates.
The paper, "Turning back time," was written by Alan Johnson of Tally Health and David Sinclair of Harvard Medical School. It pulls together 41 human studies. Here is what the authors found, what it means, and what it doesn't.
What the review actually did
Epigenetic clocks estimate biological age from DNA methylation patterns. Older "first-generation" clocks were built mainly to predict chronological age. Next-generation clocks were designed to capture how lifestyle, health, and disease make biological age diverge from the calendar. According to the authors, these newer models are more strongly associated with all-cause mortality risk.
The authors ran a series of systematic searches and found 41 human studies reporting the effect of an intervention on at least one next-generation clock. They also summarized effect sizes and compared the clocks by how often each is used and how responsive each is to intervention.
The authors still describe epigenetic clocks as investigational biomarkers. A clock going down is not the same as living longer.
The interventions that lowered epigenetic age
According to the abstract, these were linked to decreased epigenetic age:
- Exercise
- A plant-rich diet
- Semaglutide, a GLP-1 receptor agonist
- Caloric restriction
- Omega-3 fatty acids
- A multivitamin-multimineral supplement
- Ketamine
- Umbilical cord plasma
- Pitavastatin, a cholesterol-lowering drug
The list is a mix of ordinary lifestyle habits, prescription drugs, supplements, and experimental clinical procedures. The review also covers psychosocial interventions in its wider scope.
The surprise: NR, rapamycin, and senolytics did nothing
This is the headline finding. Nicotinamide riboside, rapamycin, senolytics, and several other interventions showed no detectable effect on these clocks.
All three get heavy attention in longevity circles. NR is a popular NAD+ precursor supplement. Rapamycin is a frequent subject of anti-aging discussion. Senolytics aim to clear senescent cells. Much of the excitement behind them comes from animal and cell-based work, and this review concerns human trials only.
Two caveats matter here:
- "No detectable effect" is not "no benefit." A compound could affect health through pathways these clocks don't track. Trials may also be too short, too small, or too narrowly designed to move a methylation score. The abstract doesn't settle which explanation applies.
- Clocks are imperfect yardsticks. Their responsiveness varies, which is why the authors compared clocks for sensitivity to intervention.
The warning label: some things accelerated aging
The review also reports that plasmapheresis and other therapeutics accelerated epigenetic aging. Plasmapheresis is a procedure that filters or exchanges blood plasma. That sits awkwardly beside the finding that umbilical cord plasma lowered epigenetic age. Whether the result reflects what is removed, what is added, or the measurement itself, the abstract doesn't say. It is a reminder that "blood-based rejuvenation" is not one idea.
Practical takeaways
The abstract does not give doses, timing, or durations. Those details vary by trial and sit in the full paper's tables, so check them before acting. Here is a cautious reading of who each finding is relevant to.
Low-barrier, broadly applicable
- Exercise and a plant-rich diet: The lowest-risk items on the list. Anyone cleared to be active can start. People with medical conditions should adjust with their clinician.
- Omega-3s and a multivitamin-multimineral: Accessible supplements, but check the specific formulation and dose used in the trials. Those on blood thinners should ask a clinician before adding high-dose omega-3.
- Caloric restriction: Not appropriate for everyone. Anyone who is underweight, pregnant, older and frail, or has a history of disordered eating should skip it.
Prescription-only, medical context required
- Semaglutide: A prescription drug for approved medical indications. The review doesn't support using it solely to turn back an epigenetic clock.
- Pitavastatin: A statin used for cholesterol. It belongs in a conversation about cardiovascular risk, not clock-chasing.
- Ketamine: A controlled substance given under medical supervision. It is not a longevity supplement, and this finding is no basis for self-experimentation.
Experimental
- Umbilical cord plasma and plasmapheresis: These are clinical-research territory. Given that plasmapheresis was linked to accelerated epigenetic aging, avoid commercial offerings that promise rejuvenation.
Who should reconsider their stack: People spending heavily on NR specifically to reduce epigenetic age should know the human evidence reviewed here didn't show an effect on these clocks. That doesn't mean NR is harmful or useless for other purposes.
The conflict-of-interest context
Readers should weigh the authors' interests. Johnson is employed by Tally Health, a company that sells epigenetic age testing. David Sinclair discloses roles as founder, equity owner, advisor, director, board member, consultant, or investor in several longevity firms: EdenRoc Sciences, Life Biosciences, NucleicAI, Paradigm88, and Tally Health. A company that sells epigenetic testing has a commercial interest in clocks being seen as meaningful, so the framing deserves scrutiny. It is also worth noting that the review reports null findings for popular longevity compounds. That doesn't erase the conflicts, but it cuts against a simple "sell-the-supplement" reading.
Bottom line
The most defensible reading of this review is modest. Several interventions, led by everyday behaviors, are associated with lower next-generation epigenetic age in human studies. Some highly publicized longevity compounds did not show an effect on these clocks. Epigenetic clocks are still investigational, and a better score is not proof of a longer life. Before reorganizing your routine around one, read the full paper's effect sizes and study designs.
