Omega-3 and biological age clocks: what a 3-year trial measured
A later look at a large European trial measured DNA methylation "clocks" after three years of omega-3, vitamin D and a simple home exercise programme. The clocks moved a little. The trial's clinical results barely did.
Short answer
- 777 adults aged 70 and over, from the DO-HEALTH trial, with blood samples at the start and at 3 years.
- 1 g omega-3 a day slowed several clocks by about 2.9 to 3.8 months over those three years.
- On one clock, omega-3, vitamin D and exercise added up. On the others, they did not.
- The main trial found little difference on its clinical outcomes. This was a later analysis, and the effect is small.
A clock is a marker, not the outcome
A DNA methylation clock is a lab score built from chemical marks on DNA. The score is trained to track age or the pace of aging in earlier datasets. It is a marker. It is not a diagnosis, a birthday, or proof that someone will stay well.
Bischoff-Ferrari and colleagues reported the clock analysis in Nature Aging (2025). It used 777 of the 2,157 people in DO-HEALTH, the ones with methylation data at baseline and year 3.
What the trial actually gave people
DO-HEALTH was a three-year trial in generally healthy, active adults aged 70 and over, in five European countries. The factorial design tested vitamin D (2,000 IU a day), omega-3 (1 g a day) and a simple home strength programme, alone and combined. People were not told to buy a product from this page. The doses are what the trial used, not a suggestion.
What moved, and what did not
Omega-3 alone slowed three of four next-generation clocks (PhenoAge, GrimAge2 and DunedinPACE). Across the clocks that moved, the paper puts the size at about 0.16 to 0.32 units, or 2.9 to 3.8 months, from baseline to year 3. Vitamin D alone and exercise alone did not shift the clocks. On PhenoAge, the three together added up. They did not add up on the other clocks.
The main DO-HEALTH paper in JAMA (2020) found little difference on the trial's clinical outcomes. A later marker analysis does not overwrite that. A clock that reads a few months "younger" on a lab score is not the same thing as fewer falls, a stronger body or a clearer memory. Those clinical questions were the original trial. This blog does not re-try them.
Limits
This was a secondary, post hoc look at a subset. The effect is small. Clocks disagree with each other. Three years in healthy older volunteers is not a map for every age or every product on a shelf.
This post is general information, not medical or dietary advice.
Sources
- Bischoff-Ferrari H. A. et al. (2025), omega-3, vitamin D and exercise and DNA methylation clocks in DO-HEALTH, Nature Aging. PubMed
- Bischoff-Ferrari H. A. et al. (2020), DO-HEALTH factorial trial of vitamin D, omega-3 and a strength-exercise programme, JAMA. PubMed
Video transcript
One gram of omega-3 a day for three years. What happened to biological age clocks?
This trial followed seven hundred and seventy-seven adults over seventy in Europe. Researchers later looked at DNA aging clocks.
Omega-3 slowed several clocks by about three months over three years. On one clock, omega-3, vitamin D and exercise added up.
It's a later analysis, the effect is small, and aging clocks are markers, not established health outcomes.
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This blog does not give medical advice. Health disclaimer.