EPA vs DHA comes down to structure and job. Both are long-chain omega-3 fats found in fish and fish oil, but DHA is a major building block of the brain and the retina, while EPA is better known as a starting material for signaling molecules that help regulate the body's responses. Most fish oil supplements contain both, in different amounts. Here is how the two differ, what head-to-head research shows, and how to read both numbers on a supplement label.
Key takeaways
- EPA has a 20-carbon chain with five double bonds; DHA has a 22-carbon chain with six.
- DHA is especially concentrated in the brain and the retina, where it is part of cell membranes.
- The body converts very little plant-based ALA into EPA and DHA, so food and supplements are the practical sources.
- On a label, look for EPA and DHA listed separately in milligrams per serving, not only the total fish oil.
What are EPA and DHA?
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two long-chain omega-3 fatty acids that most research focuses on. A third omega-3, ALA (alpha-linolenic acid), comes from plant foods such as flaxseed, chia and walnuts. ALA is essential, meaning the body cannot make it, but it can be converted into EPA and then DHA.
That conversion is the catch. According to the NIH Office of Dietary Supplements, the conversion is very limited, with reported rates of less than 15 percent. The body converts very little plant-based ALA into EPA and DHA, so food and supplements are the practical sources. Oily fish such as salmon, mackerel, sardines and anchovies are the richest foods.
Interestingly, fish do not make EPA and DHA themselves. Both are first made by microalgae at the base of the marine food chain and build up in fish as they eat. That is why algae oil is also a source, which we cover in our guide to fish oil vs. algae oil.
How do EPA and DHA differ?
The two fats are close relatives, but small differences in shape change where the body puts them and what they are used for.
Structure
EPA has a 20-carbon chain with five double bonds; DHA has a 22-carbon chain with six. Those extra carbons and the extra bend give DHA a more flexible shape, which suits it to tightly packed membranes that need to stay fluid.
Where the body uses them
DHA is especially concentrated in the brain and the retina, where it is part of cell membranes. The Office of Dietary Supplements notes that DHA is particularly high in the retina, brain and sperm, and that it builds up rapidly in the brain and retina before birth. EPA is present in membranes throughout the body at lower levels and is not stored in the brain to the same degree.
Signaling vs. structure
Omega-3s are also used to make eicosanoids, signaling molecules involved in the cardiovascular, immune and other systems. EPA is a direct starting material for these omega-3 eicosanoids and competes with the omega-6 fat arachidonic acid for the same enzymes. In simple terms, DHA is thought of mainly as a structural fat and EPA mainly as a signaling fat, though in reality the roles overlap.
| EPA | DHA | |
|---|---|---|
| Full name | Eicosapentaenoic acid | Docosahexaenoic acid |
| Carbon chain | 20 carbons, 5 double bonds | 22 carbons, 6 double bonds |
| Where it concentrates | Spread through cell membranes at lower levels | Brain, retina and sperm |
| Best-known role | Starting material for signaling molecules | Structural fat in membranes |
| Main sources | Oily fish, fish oil, some algae oils | Oily fish, fish oil, algae oil |
What does head-to-head research show?
Most omega-3 studies give people a mix of EPA and DHA, so it is hard to separate their effects. A smaller set of trials gives each one on its own, usually as highly purified concentrates at high doses.
A 2018 systematic review by Innes and Calder looked only at trials using at least 2 g a day of 90 percent pure EPA or DHA. Both lowered blood triglycerides, with DHA having the larger effect. DHA also raised HDL cholesterol, along with LDL cholesterol and LDL particle size, and both reduced platelet activity. The authors concluded that EPA and DHA appear to have different effects, but that larger studies are needed to confirm them.
The ComparED study, a 2016 crossover trial, gave 154 adults with abdominal obesity 2.7 g a day of either EPA or DHA for ten weeks each. DHA produced larger changes than EPA in some blood markers of inflammation and in blood lipids, including larger rises in both HDL and LDL cholesterol.
Two cautions apply. These trials used purified, single-fat products at doses far higher than an ordinary fish oil serving, and they measured blood markers in specific groups of people. They help explain how EPA and DHA differ biologically. They do not predict what a typical fish oil supplement will do for any one person.
Do you need more EPA or more DHA?
For most people the honest answer is that you do not need to pick. Fish and standard fish oil naturally provide both, and the total amount of EPA plus DHA you get regularly matters more than the exact split. The U.S. National Academy of Medicine has not set specific intake recommendations for EPA or DHA.
Products built around one fat do exist, such as DHA-focused algae oils or EPA-heavy concentrates. If someone has a specific reason to favor one, such as a recommendation from their doctor, that is a decision to make with a clinician rather than from a label alone. For the bigger picture on amounts, see our guide to how much omega-3 per day.
Two regulatory guardrails are useful to know. The FDA has concluded that dietary supplements providing no more than 5 g a day of EPA and DHA combined are safe when used as recommended, and it specifies that supplement labels should not recommend more than 2 g a day.
How to read EPA and DHA on a supplement label
On a label, look for EPA and DHA listed separately in milligrams per serving, not only the total fish oil. Here is a simple routine:
- Find the serving size. Many fish oils use two softgels per serving. Every number on the panel refers to that serving.
- Find the EPA and DHA lines. They should be listed in milligrams. If a label shows only "fish oil 1,000 mg", you cannot tell how much omega-3 you are getting.
- Add them together. EPA plus DHA is the figure most research and guidance refers to.
- Compare with the fish oil total. The gap between total oil and EPA plus DHA tells you how concentrated the oil is.
- Check the ratio. Dividing EPA by DHA shows the balance, which varies between products.
A worked example: Pure Omega+™
The Pure Omega+™ panel shows a two-softgel serving. Per serving it lists 2,400 mg of fish oil, 1,440 mg of omega-3, 864 mg of EPA and 576 mg of DHA. The EPA and DHA add up to exactly the 1,440 mg omega-3 figure, and the split is roughly three parts EPA to two parts DHA. Our article Inside Pure Omega+ walks through the rest of that panel line by line.
Where Pure Omega+ fits
Pure Omega+ is a lemon-flavored fish oil from anchovy, in a gelatin softgel. The suggested use is two softgels daily with meals, and the 60-softgel bottle is a 30-day supply. It is formulated to contribute to a healthy heart, support joint flexibility, promote brain and nerve function, support vision health and aid in memory care.*
Every batch is third-party tested for purity and potency, and it is bottled in an NSF-certified, GMP-certified, FDA-registered U.S. facility. See our standards for what that testing covers.
Safety notes
The label states: Contains: Fish (Anchovy). May contain porcine. Do not exceed recommended dose. Pregnant or nursing mothers, children under the age of 18, and individuals with a known medical condition should consult a physician before using this or any dietary supplement.
The Office of Dietary Supplements notes that fish oil can have antiplatelet effects at high doses and may affect clotting time in people taking warfarin. If you take a blood thinner or any prescription medicine, check with your healthcare provider first. Common side effects of omega-3 supplements are usually mild, such as an unpleasant taste, heartburn or an upset stomach.
Frequently asked questions about EPA vs DHA
Is EPA or DHA better?
Neither is better across the board. They have different structures and roles, and most fish oils supply both. The total amount of EPA plus DHA you take regularly matters more for most people than the exact ratio.
What is the main difference between EPA and DHA?
DHA is a structural fat that is especially concentrated in the brain and the retina. EPA is better known as a starting material for signaling molecules. DHA is also slightly larger, with 22 carbons to EPA's 20.
Can I get EPA and DHA from plant foods?
Plant foods supply ALA, which the body converts into EPA and DHA only in small amounts. Algae oil is the main plant-based source that provides DHA directly, and some algae oils also contain EPA.
Should the omega-3 total equal EPA plus DHA?
Not always. Some labels count other omega-3 fats in the total, so it can be higher than EPA plus DHA. On the Pure Omega+ panel, EPA and DHA together make up the full omega-3 figure.
Is it safe to take EPA and DHA every day?
For most healthy adults, taking a fish oil supplement daily as directed on the label is the usual approach. If you take a blood thinner, are pregnant or nursing, or have a medical condition, talk with your healthcare provider first.
Related reading from our Wellness Hub
- How Much Omega-3 Per Day? EPA and DHA Amounts Explained
- How to Choose a Fish Oil Supplement: Five Label Details That Matter
- Fish Oil vs. Algae Oil: Which Omega-3 Source Fits You?
Sources
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids, Fact Sheet for Health Professionals
- Innes JK, Calder PC. The differential effects of EPA and DHA on cardiometabolic risk factors: a systematic review. Int J Mol Sci, 2018
- Allaire J, et al. A randomized, crossover, head-to-head comparison of EPA and DHA supplementation (ComparED Study). Am J Clin Nutr, 2016
- National Center for Complementary and Integrative Health: Omega-3 Supplements, What You Need To Know
Individual results vary.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
