Omega-3 EPA/DHA
Omega-3 fatty acids have been studied for decades, particularly for heart and brain health. The two that receive the most attention are EPA and DHA, found primarily in fatty fish and fish-oil supplements.
There is little controversy that EPA and DHA are important nutrients. The more difficult question is whether people who already eat reasonably well benefit from taking additional omega-3 supplements.
Eating fish is consistently associated with better health, while clinical trials of omega-3 supplements have produced mixed results. Dose, the amount of EPA and DHA already in the diet, and a person's underlying health may all matter.
For older adults, I think the most interesting questions are: How much EPA and DHA do we need? Is eating fish enough? And is there convincing evidence that supplements protect the heart or brain?
EPA and DHA — What’s the Difference?
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are long-chain omega-3 fatty acids found mainly in fatty fish such as salmon, sardines, mackerel and herring.
EPA is often associated with cardiovascular health and inflammation, while DHA is particularly important in the brain and retina. Both are incorporated into cell membranes and have overlapping roles throughout the body.
The body can make some EPA and DHA from the plant omega-3 ALA, found in foods such as walnuts and flaxseed, but the conversion is limited. That is why fish and marine omega-3 supplements are the primary direct sources of EPA and DHA.
What About Inflammation?
EPA and DHA also have anti-inflammatory effects. They become incorporated into cell membranes and influence the signaling molecules involved in the body's inflammatory response.
Clinical trials suggest that omega-3 supplementation can reduce some markers of inflammation, including CRP, IL-6 and TNF-alpha, particularly in people who already have elevated inflammation or certain chronic health conditions.
The effect is not consistent in everyone, however. In healthy people with low levels of inflammation, omega-3 supplements may produce little measurable change.
This makes reduced inflammation a plausible benefit of omega-3s, but not a reason to assume that everyone needs a high-dose supplement.
What Does the Evidence Show for Heart Health?
Omega-3s have a well-established effect on lowering triglycerides, particularly at higher doses. But whether ordinary fish-oil supplements prevent heart attacks and strokes is less clear.
Large randomized trials of commonly used omega-3 supplements have generally found little or no reduction in major cardiovascular events in people who are not at particularly high risk.
One notable exception is icosapent ethyl (Vascepa), a prescription form of highly purified EPA. In the REDUCE-IT trial, high-risk patients with elevated triglycerides who were already taking statins had significantly fewer cardiovascular events when given high-dose EPA.
That doesn't mean an ordinary fish-oil capsule provides the same benefit. The formulation, dose and person taking it matter.
For most people, the strongest evidence still supports regularly eating fatty fish rather than relying on a supplement to prevent cardiovascular disease.
What About Brain Health?
DHA is an important structural component of the brain and plays a role in maintaining healthy brain-cell membranes. That makes getting enough DHA particularly interesting as we age.
People who regularly eat fish tend to have a lower risk of cognitive decline in observational studies. Randomized trials of omega-3 supplements have produced mixed results, but that doesn't necessarily mean supplementation has no value.
Benefits may depend on how much omega-3 a person already consumes, the dose and duration of supplementation, and when in life supplementation begins. Researchers are also investigating whether genetics—particularly APOE4 status—may influence how the brain responds to DHA.
For people who don't regularly eat fatty fish, an EPA/DHA supplement provides a practical way to increase omega-3 intake. Whether supplementation actually prevents Alzheimer’s disease remains uncertain, but maintaining adequate EPA and DHA seems a reasonable goal for healthy aging.
Fish or Supplements?
Fatty fish provides EPA and DHA along with protein, vitamin D, selenium and other nutrients, so eating fish has advantages that a capsule cannot completely duplicate.
For people who eat fatty fish regularly, additional supplementation may not be necessary. But for people who rarely eat fish—or simply don't like it—an EPA/DHA supplement can be a practical way to maintain omega-3 intake.
When choosing a supplement, look at the amounts of EPA and DHA, not simply the amount of “fish oil” printed on the front of the bottle. A capsule labeled 1,000 mg fish oil may provide only a fraction of that amount as EPA and DHA.
Wild-Caught or Farm-Raised?
I generally prefer wild-caught fish, but the nutritional comparison with farm-raised fish isn't as simple as I once assumed.
Wild salmon is typically leaner and its diet comes from its natural environment. Farm-raised Atlantic salmon generally contains more total fat and can contain as much or more EPA and DHA per serving, although the amount varies with the feed used.
There are also questions about contaminants, sustainability and farming practices that go beyond omega-3 content.
My preference remains wild-caught when it is readily available, but both wild and responsibly farm-raised salmon can be excellent sources of EPA and DHA.
The Omega-3 Index — Are You Getting Enough?
The Omega-3 Index, developed by researchers William Harris and Clemens von Schacky, measures EPA and DHA in red blood cells, reflecting omega-3 status over several months.
Researchers have proposed these ranges:
Below 4%: Low
4–8%: Intermediate
Above 8%: Desirable
Higher levels are associated with lower cardiovascular risk, although it remains uncertain whether raising the index through supplements prevents heart attacks or strokes.
For people taking omega-3 supplements, the test offers a practical way to measure their omega-3 status.
Risks and Cautions
Omega-3 supplements are generally well tolerated, but higher doses aren't necessarily better. Some cardiovascular trials have found an increased risk of atrial fibrillation (AFib), particularly at higher doses of EPA and DHA.
People with a history of AFib or other heart rhythm problems, and those taking anticoagulants or other medications that affect bleeding, should discuss omega-3 supplementation with their healthcare provider.
Learn More
A detailed evidence-based review of EPA, DHA and other omega-3 fatty acids, including food sources, supplements, cardiovascular disease, cognitive health and safety.
Practical guidance on eating fish and the role of omega-3 fatty acids in cardiovascular health.
Videos
Rhonda Patrick, Ph.D. discusses the evidence for omega-3 fatty acids and their potential roles in cardiovascular and brain health.
Nick Norwitz talks with Professor William Harris, a longtime omega-3 researcher and developer of the Omega-3 Index, about the research on EPA and DHA, omega-3 blood levels, supplementation, and cardiovascular health.