“Biological age: 38 – even though you are 52.” Results like these are promised by commercial tests that read so-called epigenetic clocks from blood samples. But how reliably do these clocks respond to diet, exercise, medicines or supplements? An analysis published in Nature Medicine in August 2026 provides a sobering but revealing answer.
What are epigenetic clocks?
Over the course of life, chemical marks on our DNA change, above all so-called methylations. Age estimates can be calculated from these patterns using mathematical models. The first generation (such as the Horvath or Hannum clock) was trained to predict chronological age. Newer clocks such as DunedinPACE or GrimAge, by contrast, are intended to reflect the pace of ageing or the risk of death.
The study
Researchers at Yale University and other institutions re-analysed 51 intervention studies in humans with a total of 3,128 blood samples – using a uniform method and 16 different epigenetic clocks as well as 94 other biomarkers. Several authors are affiliated with the test provider TruDiagnostic, which supplied data.
The results
- 19 of 51 measures significantly reduced epigenetic age (13 after strict statistical correction).
- 5 measures increased it.
- 26 showed no measurable effect.
- Senolytics – agents intended to eliminate aged “zombie cells” – produced contradictory results in five studies, sometimes in opposite directions.
- Consistent changes were shown, among others, by anti-TNF therapies (anti-inflammatory medicines) and two Mediterranean diet protocols in healthy people.
- Overall, medicines produced larger effects than lifestyle changes or dietary supplements.
- In people with existing diseases, the clocks responded more strongly than in healthy people.
The newer second-generation clocks proved considerably more reliable than the early models, which tended to respond erratically.
What the results do not mean
The authors explicitly warn against misinterpretation: the fact that a clock responds to a measure is only a prerequisite for using it in future as an outcome measure in studies – not proof that someone actually lives longer or healthier. The measured effects were also rather small (in the order of about one year), and there is as yet no defined threshold above which a change is clinically meaningful. Some clocks include inflammatory markers such as C-reactive protein and might therefore reflect inflammation rather than ageing.
Conclusion for consumers
A lower value on a commercial “biological age” test does not mean that you have become biologically younger. The study is primarily intended to help plan future ageing studies better – not as a basis for decisions about buying supplements. For healthy ageing, the well-known fundamentals remain decisive: exercise, a balanced diet, not smoking and the treatment of chronic diseases.
Note: This article is for general information only and does not replace medical advice.
