Omega-3: EPA vs DHA vs ALA, How Much You Need, and Which Fish Oil Form to Buy

Omega-3 fatty acids are polyunsaturated fats your body needs but cannot make enough of. The three that matter are ALA from plants, and EPA and DHA from fish, algae and fish oil. Adults need 1.1–1.6 g of ALA daily, but the body converts less than 15% of it to EPA and DHA, so eating fish or taking fish or algal oil is the practical way to raise them.

EPA vs DHA vs ALA, and Triglyceride vs Ethyl Ester Fish Oil

Bioavailability figures are relative increases in serum EPA+DHA in 72 volunteers taking about 3.3 g/day EPA+DHA for 2 weeks (Dyerberg et al., 2010). NIH ODS adds that all forms significantly raise plasma EPA and DHA. Other figures: NIH ODS omega-3 fact sheet.

What are omega-3 fatty acids?

Omega-3s are polyunsaturated fats with their first double bond three carbons from the end of the chain. The body cannot insert a double bond in that position, which is why ALA is essential: it must come from food. EPA and DHA are the long-chain omega-3s. They are originally made by microalgae and build up in fish through the food chain, which is why algal oil is a direct vegan source. Omega-3s form part of every cell membrane and are the raw material for signalling molecules that affect the heart, blood vessels, lungs and immune system (NIH ODS).

How much omega-3 do you need per day?

The only official US intake values are for ALA: an Adequate Intake of 1.6 g/day for men and 1.1 g/day for women (1.4 g in pregnancy, 1.3 g breastfeeding). The Institute of Medicine set no target for EPA or DHA. The European Food Safety Authority recommends 250 mg/day of EPA plus DHA for adults, plus an extra 100–200 mg/day of DHA in pregnancy. For people with existing coronary heart disease, the American Heart Association suggests about 1 g/day of EPA plus DHA, preferably from oily fish. Treating high triglycerides uses 4 g/day prescription omega-3s under a doctor.

EPA vs DHA: which do you need?

Most people do not need to choose; fish and most fish oils contain both. A typical 1,000 mg fish oil capsule provides about 180 mg EPA and 120 mg DHA, per NIH ODS, so read the label for EPA + DHA, not “fish oil”. DHA is the priority in pregnancy because it builds the fetal brain and retina, and DHA supplements reduce preterm birth. The strongest heart-outcome trial, REDUCE-IT, used pure EPA as a prescription drug, so EPA-only results should not be assumed for DHA.

Is plant omega-3 (ALA) enough?

For the essential requirement, yes: most Americans meet the ALA AI from food, averaging about 1.59 g/day for women and 2.06 g/day for men. For EPA and DHA, no. NIH ODS reports ALA-to-EPA/DHA conversion of less than 15%, and EPA plus DHA from food averages only about 90 mg/day in US adults. Vegans who want EPA and DHA should use algal oil, which NIH says provides DHA as bioavailable as cooked salmon in a small study.

Triglyceride vs ethyl ester fish oil

Concentrated fish oils are made by converting the natural triglycerides to ethyl esters, and sometimes back again to re-esterified triglycerides. In a head-to-head trial, re-esterified triglycerides gave 124% of the EPA+DHA uptake of natural fish oil, while ethyl esters gave 73% (Dyerberg 2010). The practical gap narrows when ethyl esters are taken with a fatty meal, and NIH notes every form raises blood levels significantly. Cost per mg of EPA+DHA usually matters more than form.

Best omega-3 by need

A form ranking, not a paid brand ranking.

• Best overall: one to two servings of seafood a week, as the American Heart Association recommends.
• Best supplement for most people: a fish oil listing at least 250 mg EPA + DHA per serving (the EFSA reference), triglyceride or ethyl ester taken with food.
• Best for vegans and pregnancy if you avoid fish: algal oil, typically 100–300 mg DHA per serving. See fish oil vs algae oil.
• Krill oil: phospholipid form; NIH says bioavailability studies are mixed, and doses per capsule are lower. See fish oil vs krill oil.
• High triglycerides or high heart risk: prescription omega-3s from your doctor, not supplements.

Does omega-3 protect your heart?

It depends who you are and the dose. In VITAL, 25,871 healthy older adults taking 1 g/day (460 mg EPA, 380 mg DHA) for a median 5.3 years had no significant drop in major cardiovascular events or cancer versus placebo (Manson 2019), though heart attacks were 28% lower in a secondary outcome. In REDUCE-IT, 4 g/day of prescription icosapent ethyl cut cardiovascular events by 25% in statin-treated patients with high triglycerides. The STRENGTH trial of 4 g/day EPA+DHA in a different form found no benefit. NIH concludes fish oil lowers triglycerides and evidence of protection is stronger for people with existing coronary heart disease.

Omega-3 in pregnancy

A 2018 Cochrane Review of 70 trials found long-chain omega-3s during pregnancy reduced preterm birth (before 37 weeks) by 11% and early preterm birth (before 34 weeks) by 42%. ACOG and FDA advise 8–12 ounces a week of lower-mercury seafood such as salmon, sardines and trout. NIH ODS notes omega-3 supplements have not been found to contain methylmercury because it is removed in processing.

Omega-3 side effects, safety and interactions

No Tolerable Upper Intake Level has been set. EFSA judged long-term EPA+DHA up to about 5 g/day safe, and FDA has concluded supplements supplying no more than 5 g/day are safe as recommended. Two large trials of 4 g/day slightly raised atrial fibrillation risk in people with or at high risk of heart disease. Common side effects are mild: fishy taste, burps, heartburn, nausea and loose stools. Fish oil can have antiplatelet effects at high doses; most research shows 3–6 g/day does not significantly change warfarin control, but people on anticoagulants should have their INR monitored.

Omega-3 FAQ

What is the difference between omega-3 and fish oil?

Omega-3 is the family of fatty acids (ALA, EPA and DHA). Fish oil is one source of omega-3s, mainly EPA and DHA. A typical 1,000 mg fish oil capsule contains about 180 mg EPA and 120 mg DHA, so check the EPA plus DHA total on the label.

How much omega-3 should I take daily?

US guidance sets ALA needs at 1.6 g a day for men and 1.1 g a day for women. There is no US target for EPA and DHA; EFSA recommends 250 mg a day of EPA plus DHA for adults, with an extra 100 to 200 mg of DHA in pregnancy.

Is EPA or DHA more important?

Both matter. DHA is a structural fat in the brain and retina and is the priority in pregnancy. EPA is the omega-3 used in the REDUCE-IT prescription trial that reduced cardiovascular events. Most fish oils provide both.

Can I get enough omega-3 from flaxseed or chia?

You can meet your ALA needs, but not your EPA and DHA. The body converts less than 15 percent of ALA into EPA and DHA, so vegans who want EPA and DHA should consider algal oil.

Is triglyceride fish oil better than ethyl ester?

It is absorbed somewhat better. In a 2010 trial, re-esterified triglyceride fish oil gave 124 percent of the EPA and DHA uptake of natural fish oil, while ethyl esters gave 73 percent. All forms raise blood levels, especially when taken with a meal.

Is krill oil better than fish oil?

Not clearly. Krill oil provides omega-3s as phospholipids, and NIH says some studies suggest higher bioavailability while others do not. Krill capsules usually contain less EPA and DHA per serving.

Does omega-3 reduce heart attack risk?

In healthy people, 1 g a day did not reduce major cardiovascular events overall in the VITAL trial. High-dose prescription EPA reduced events by 25 percent in high-risk statin users in REDUCE-IT. Evidence is strongest for people who already have heart disease.

What is the maximum safe dose of omega-3?

No official upper limit exists. EFSA and FDA consider up to about 5 g a day of EPA plus DHA from supplements safe. Doses of 4 g a day slightly increased atrial fibrillation risk in high-risk patients.

Should I take omega-3 if I am on blood thinners?

Ask your prescriber first. Most research shows 3 to 6 g a day of fish oil does not significantly affect warfarin, but FDA labels for prescription omega-3s advise periodic INR monitoring when combined with anticoagulants.

Sources

1. NIH Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals
2. Dyerberg J, et al. Bioavailability of marine n-3 fatty acid formulations. Prostaglandins Leukot Essent Fatty Acids. 2010;83(3):137-41
3. Manson JE, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer (VITAL). N Engl J Med. 2019;380(1):23-32
4. Bhatt DL, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia (REDUCE-IT). N Engl J Med. 2019;380(1):11-22