What EPA and DHA Do: The Evidence and What Labels May Say

EPA and DHA are the long-chain omega-3 fats found in seafood, fish oil and algal oil. This guide explains what public health bodies say about them, what research reviews have found and which health-related wording FDA has said it will tolerate on labels. It is general information for healthy adults, not medical advice, and nothing here promises a result. For the buying checks, see our guide to choosing an omega-3 supplement.

Three omega-3s, two that matter for supplements

NCCIH names the three. ALA (alpha-linolenic acid) is found in plant oils such as flaxseed, soybean and canola, and in chia seeds and walnuts. EPA and DHA are found in seafood, especially cold-water fish, and in fish oil supplements. The Linus Pauling Institute (LPI) says omega-3 fats are structural components of cell membranes, and that the body can make EPA and DHA from ALA but inefficiently: in the studies it summarizes, about 8% of dietary ALA became EPA and 0% to 4% became DHA in young men, and about 21% and 9% in young women. LPI therefore advises getting EPA and DHA from additional sources. The scientific report behind the 2025-2030 Dietary Guidelines for Americans says EPA and DHA are built into cell membranes throughout the body, and that DHA may be particularly important for neurodevelopment.

How much people get and what is suggested

The same report puts average American intake at about 110 mg of EPA and DHA a day. The National Academies set Adequate Intakes for ALA, 1.6 g a day for men and 1.1 g for women, but LPI's table gives no separate figure for EPA and DHA in adults. LPI cites expert panels suggesting about 250 mg a day of EPA and DHA for adults in general and at least 200 mg of DHA a day in pregnancy and breastfeeding; those are expert recommendations, not label requirements. The AHA recommends two 3-ounce servings of fish a week, particularly fatty fish, and NCCIH reports that the 2020-2025 Dietary Guidelines advise 8 ounces or more of seafood a week.

What the research reviews found

NCCIH's omega-3 page, updated in November 2024, summarizes reviews in plain terms. We repeat them as research findings, not as promises:

• Heart and stroke. A 2020 review of 86 studies with 162,796 people found that increasing EPA and DHA slightly reduced coronary events and coronary death, while a 2020 review of 31 trials found omega-3 supplements had little or no effect on strokes. NCCIH adds that a 2021 analysis saw a lower stroke risk only at high doses, from just two studies, so no firm conclusion can be drawn. NCCIH says there is some evidence that people with heart disease or high triglycerides may benefit.
• Triglycerides. A 2020 review of 23 studies found EPA and DHA lowered triglycerides by about 15%, with no effect on body fat or other blood fats.
• Mood and attention. NCCIH calls it uncertain whether supplements help with depression, and a 2023 review found no evidence that ADHD symptoms are likely to improve in children and adolescents.
• Pregnancy. A 2020 review for the Dietary Guidelines advisory committee found limited evidence that supplements in pregnancy affect children's cognitive development.

NCCIH also notes that other nutrients in seafood, and what people eat instead of less healthful foods, may contribute to seafood's benefits, so seafood results do not automatically carry over to capsules.

What FDA has said about health claims

In the US, a statement that a food component reduces the risk of a disease is a health claim. For EPA and DHA, FDA's 2019 announcement says the evidence did not meet the "significant scientific agreement" standard required for an authorized claim but did meet the "credible evidence" standard for a qualified one. A qualified claim carries wording about how limited the evidence is, and FDA used enforcement discretion: it does not intend to object to the claim if it is used consistent with the factors in its letter. That is not approval.

FDA says that since 2004 it has exercised enforcement discretion, under certain circumstances, for this wording: "Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease".

In June 2019 it listed five more wordings about blood pressure, hypertension and coronary heart disease. The first reads: "Consuming EPA and DHA combined may help lower blood pressure in the general population and reduce the risk of hypertension. However, FDA has concluded that the evidence is inconsistent and inconclusive. One serving of [name of the food or dietary supplement] provides [ ] gram(s) of EPA and DHA." All five carry the same "However" sentence. These are FDA's words, not claims we make.

The conditions matter as much as the words. For the 2019 wordings, FDA said a product should provide at least 0.8 g of EPA and DHA combined per serving, that a supplement bearing the claim should provide no more than 5 g a day when used as labeled, and that the amount per serving should be stated in the claim or, for supplements, in the Supplement Facts panel. FDA's letter lists further factors too; for supplements they include no more than 1 g of saturated fat per reference amount customarily consumed (the amount FDA sets for one eating occasion) and, for forms other than liquids, such as softgels and gummies, no more than 20 mg of cholesterol per reference amount. A product with a few hundred milligrams per serving falls below the 0.8 g line. A label that drops the "However" sentence, or promises more than these wordings, is not using what FDA described.

Structure and function statements

Most supplement labels use a different route. FDA says a structure/function claim may describe the role of a nutrient in the body's normal structure or function, such as "calcium builds strong bones." These claims are not approved beforehand: the manufacturer must have substantiation, must notify FDA within 30 days of marketing, and the label must carry a disclaimer that FDA has not evaluated the claim and that the product is not intended to diagnose, treat, cure or prevent any disease. A supplement represented as treating or preventing a disease is regulated as a drug. So a label may say something general about EPA or DHA in the body, but a disease promise on a supplement is a warning sign.

Using this when you shop

Look for the EPA and DHA lines in grams or milligrams per serving, check the serving size, and compare any health wording with the quotations above. A label with no claim at all is not a bad sign, since the amounts on the panel are what you compare. Searches such as fish oil softgels with EPA and DHA on Amazon (opens in a new tab) and algal oil with DHA on Amazon (opens in a new tab) list many options, and the label on the pack, not the listing, is what counts.

For sources and forms, see fish oil vs algae oil. For freshness, mercury and label reading, see omega-3 oxidation, mercury and labels.

Who should ask first

Talk to a doctor or pharmacist before you start if you are pregnant or breastfeeding, take medicine that affects blood clotting, are allergic to fish or shellfish, have a heart rhythm condition, or are thinking of giving a child a supplement. NCCIH lists all of these except the heart rhythm condition, which comes from the Lovaza and Vascepa labels, and FDA advises everyone to check with a health care professional before using a supplement, since some interact with medicines. The label is the authority on your product's dose and warnings, and a doctor or pharmacist is the right person to ask about your own health.