Omega-3s are healthy fats found mainly in oily fish. In VITAL, a trial of nearly 26,000 healthy adults, daily fish oil didn't significantly reduce heart attacks, strokes or cancer overall. But in 2025, an analysis of the DO-HEALTH trial in adults over 70 found 1 gram a day slowed DNA-based aging clocks by roughly three months over three years, more when combined with vitamin D and exercise. Small effects, real signal. If you rarely eat oily fish, omega-3 is reasonable; if you eat fish twice a week, you may not need it. High doses can raise the risk of an irregular heartbeat in some people.
- SymptomInflamed, faster-aging tissues
- Before thatChronic, low-grade inflammation that never switches off
- Before thatCell membranes and signals built from the "wrong" fats
- RootToo little omega-3 in a modern diet
What omega-3s are
Omega-3s are a family of fats your body can't make in useful amounts, so they have to come from food. The two most important, EPA and DHA, come mainly from oily fish. They become part of the walls around every cell and are used to make signals that help switch inflammation, the body's alarm-and-repair response, back off after it's done its job.
That's the upstream logic: a lot of aging is driven by low-grade inflammation that never fully switches off. More omega-3 might help close that loop.
Round 1: the big disappointment
VITAL followed nearly 26,000 healthy US adults for about five years. Half took 1 gram of fish oil a day, half took a placebo, a dummy pill. The fish oil group did not have significantly fewer major heart events, cancers or deaths.[1] For the idea that everyone should take fish oil as heart insurance, that was a big blow.
Round 2: the aging clock
DO-HEALTH was a three-year trial in Swiss and European adults aged 70 and over, testing vitamin D, omega-3 and a simple home exercise program. In 2025, researchers analyzed blood samples using epigenetic clocks, tests that estimate how fast your body is aging from chemical marks on your DNA.
Omega-3 alone slowed several of these clocks by roughly three months over three years. Combining omega-3, vitamin D and exercise had the biggest effect.[2] Important caveats: it was an analysis done after the trial, the effect is small, and scientists don't yet agree on which aging clock matters most.
Fish oil protects everyone's heart.
In healthy people, no significant heart benefit in a huge trial. But a small slowing of biological aging in older adults. Different outcomes, different answers.
One real risk
In a trial of high-dose omega-3 in people at high heart risk, the omega-3 group had more atrial fibrillation, a common irregular heartbeat, than the comparison group.[3] VITAL, using a normal 1-gram dose in healthy people, didn't find this. The pattern suggests the risk rises with dose, which is a good reason not to megadose.
Who might benefit
You rarely eat oily fish
A · Small effectsA 1-gram supplement fills the gap and may slightly slow biological aging, especially with vitamin D and exercise.
You eat oily fish twice a week
B · Likely enoughFood already gives you a good dose, plus protein and other nutrients.
You have heart rhythm problems or take blood thinners
Talk to a doctorHigher doses may raise atrial fibrillation risk and can add to bleeding risk.
The bottom line
Omega-3 isn't the heart shield it was sold as for healthy people, but it's not useless either: the newest data suggests a small slowing of biological aging in older adults, especially alongside vitamin D and exercise. Eat oily fish if you can; supplement around 1 gram a day if you can't; avoid megadoses. For vitamin D's side of the story, read vitamin D and K2 together.
Frequently asked questions
How much omega-3 should I take?
The aging study used 1 gram a day of omega-3 fats. Many people get enough from two servings of oily fish a week. Higher doses should be discussed with a doctor.
Is fish oil good for the heart?
In healthy people without high risk, the large VITAL trial found no significant reduction in major heart events overall. Some prescription omega-3 treatments are used for specific heart patients under medical care, which is a different situation.
Can omega-3 supplements cause atrial fibrillation?
Some trials of high doses in people at high heart risk found more atrial fibrillation, an irregular heartbeat. At typical doses in healthy people, VITAL didn't find an increase. Discuss with a doctor if you have heart rhythm problems.
What are the best food sources of omega-3?
Oily fish like salmon, sardines, mackerel, herring and anchovies are the richest sources of the most useful forms. Plant sources such as flaxseed and walnuts provide a form the body converts only in small amounts.
Sources
- Manson JE, et al. Marine n−3 fatty acids and prevention of cardiovascular disease and cancer. New England Journal of Medicine, 2019.
- Bischoff-Ferrari HA, et al. Individual and additive effects of vitamin D, omega-3 and exercise on DNA methylation clocks of biological aging in older adults from the DO-HEALTH trial. Nature Aging, 2025.
- Nicholls SJ, et al. Effect of high-dose omega-3 fatty acids vs corn oil on major adverse cardiovascular events in patients at high cardiovascular risk: the STRENGTH randomized clinical trial. JAMA, 2020.