What are omega-3 EPA and DHA?

Omega-3 fatty acids are a family of essential polyunsaturated fats important for human health. 

The three main omega-3s are:

• ALA (alpha-linolenic acid),
• EPA (eicosapentaenoic acid), and
• DHA (docosahexaenoic acid)

ALA is found in plant oils (flaxseed, soybean, canola) and must be obtained from food, but our bodies convert only a small fraction of ALA into EPA and DHA.

In contrast, EPA and DHA come mostly from marine sources (cold-water fish and algae). Because the conversion from ALA to EPA/DHA is inefficient, the best way to raise blood levels of EPA and DHA is to eat them directly – in oily fish or supplements.

EPA and DHA are critical building blocks for cell membranes and play roles in many body systems (heart, vessels, brain, eyes, immune, hormones). Notably, DHA is highly concentrated in the brain and retina, making these omega-3s essential for neurological and visual development.

Cardiovascular health benefits

Omega-3 EPA and DHA have the strongest evidence of benefit for heart health. Clinical studies show that these fats can help the heart beat more steadily and reduce dangerous arrhythmias. They also help lower blood pressure and heart rate, improve blood vessel function, and (at higher doses) reduce triglyceride levels and systemic inflammation.

For example, EPA and DHA supplements consistently cut triglycerides by about 15% on average. In practice, the American Heart Association (AHA) recommends eating oily fish rich in EPA/DHA (like salmon, mackerel, tuna or sardines) one to two times per week to protect the heart.

For people with documented heart disease, the AHA advises about 1 gram per day of EPA + DHA (preferably from fish, or under medical supervision as a supplement). These guidelines echo government advice that eating more fish (about 3.5–5 ounces) weekly is linked to lower risk of heart attack and stroke. Recent analyses even suggest that higher intakes (around 2–3 grams per day) of combined EPA+DHA can modestly reduce blood pressure. In summary, EPA and DHA contribute to heart health by stabilizing heart rhythms, lowering triglycerides, and modestly lowering blood pressure.

Brain and eye health

DHA and EPA are major structural fats in the brain and eyes.

DHA, in particular, is the most abundant omega-3 in the brain and the retina. During fetal development and early life, DHA supports brain and nervous-system formation. Indeed, experts note that from the third trimester through the second year, a growing child needs a steady supply of DHA to build brain tissue (DHA is the predominant fatty acid in brain cell membranes). Pregnant and nursing women are therefore encouraged to include DHA-rich foods or supplements.

In adults, some studies suggest that higher omega-3 intake is linked to better cognitive health. For example, people who regularly eat fatty fish tend to have a lower risk of Alzheimer’s disease, dementia, and age-related memory decline. Similarly, DHA is vital for eye health: the retina has one of the highest concentrations of DHA in the body, which helps maintain normal visual function. Observational data hint that diets rich in omega-3s (from fish) may reduce the risk of age-related macular degeneration. (However, once macular degeneration is established, trials show that taking omega-3 supplements does not slow its progression.)

In short, EPA and DHA support brain and eye function – DHA is literally built into neural and retinal tissue – and higher dietary intake may correlate with preserved cognition and vision as people age.

Mental health and mood

Omega-3s may also influence mental well-being and mood. Some research has found that people with depression or other mood disorders often have lower blood levels of EPA/DHA. Although studies are mixed, a few meta-analyses suggest modest benefits of omega-3s (especially EPA-rich formulations) in reducing depressive symptoms.

For instance, a review noted that if omega-3s help with depression, the effect size is small and evidence is low quality; many researchers recommend more data. There is some indication that high EPA (relative to DHA) might be more beneficial for mood, and that omega-3s could be used alongside antidepressants, but not as a replacement.

Omega-3s have also been studied in anxiety and ADHD. There’s some evidence (but still uncertain) that low omega-3 intake is associated with ADHD and that supplements could help, though results are inconsistent.

In pregnancy, a review found that women with higher DHA intakes tended to have slightly fewer depression/anxiety symptoms during pregnancy, but not after birth. Overall, omega-3s may play a supportive role in mental health, but the data are mixed and more research is needed.

At minimum, ensuring adequate EPA/DHA (through diet or supplements) is a low-risk step people take for mood support, though it should complement standard treatments when needed.

Natural dietary sources of EPA and DHA

Obtaining EPA and DHA from foods is ideal. The best sources are cold-water fatty fish and seafood, because fish accumulate EPA/DHA by eating microalgae. Top omega-3 foods include:

• Fatty fish: Salmon, mackerel, herring, sardines, anchovies, trout, tuna and similar oily fish provide large amounts of EPA and DHA.
• Shellfish: Oysters, mussels, and shrimp also contain some EPA/DHA (though in smaller amounts than fatty fish).
• Algal sources: Microalgae (used in some supplements) are the original producers of EPA/DHA. Vegetarian versions of DHA/EPA come from algal oil or whole algae-based foods. (In fact, fish get their omega-3s from eating algae.)
• Fortified foods: Certain products are enriched with omega-3s. For example, some eggs, milk, yogurt, juices and margarines are fortified with DHA/EPA. Since 2002, infant formulas in the U.S. have added DHA (and arachidonic acid) because of their importance for brain and eye development.
• Plant sources (ALA): Flaxseed, chia seeds, walnuts and flax/canola oils provide ALA, which can convert (inefficiently) to EPA/DHA. While ALA is beneficial on its own, relying on ALA alone to meet EPA/DHA needs may not be sufficient for optimal levels.

Including at least two servings (170 g or more) of fatty fish per week is an easy way to boost EPA/DHA intake. This amount roughly provides 250–500 mg/day on average. Vegan diets can focus on algal oil supplements or fortified foods to get their EPA/DHA.

Omega-3 supplements: fish oil, krill oil, and algal oil

For those who do not eat enough seafood, omega-3 supplements are a convenient alternative. Common supplement types include fish oil, krill oil, and algal oil. Each has pros and cons:

• Fish oil supplements: These capsules (often softgels) contain concentrated EPA and DHA, typically derived from fish like anchovy or salmon. Fish oil is inexpensive and widely available, with high levels of EPA/DHA per serving. Most fish oil supplements provide around 300 mg of EPA/DHA per 1-gram capsule.
  Pros: well-studied, cost-effective.
  Cons: It can have a “fishy” taste or cause burping, and if not purified, low-quality products might contain trace contaminants. Always choose purified, high-quality brands.
• Krill oil supplements: Krill (tiny shrimp-like crustaceans) are another marine source of EPA/DHA. The omega-3s in krill oil are bound to phospholipids, which some studies suggest is better absorbed than fish oil’s triglycerides. Krill oil naturally contains the antioxidant astaxanthin, making it more resistant to oxidation. Also, because krill are small with short lifespans, they tend to accumulate fewer toxins (like mercury) than large fish.
  Pros: better bioavailability, includes astaxanthin; less contamination.
  Cons: often more expensive, yields smaller total EPA/DHA dose per capsule, and sustainability of krill harvesting is a consideration.
• Algal oil supplements: Derived from marine microalgae, algal oil is pure EPA/DHA (mostly DHA) and is a true vegetarian/vegan source. Since algae are the original producers of EPA and DHA, algal oil directly supplies these fats without needing fish. Algal supplements are guaranteed free of mercury or PCBs (no ocean contamination) and are considered sustainable.
  Pros: plant-based, contaminant-free DHA/EPA (some also contain EPA); great for vegans and those avoiding fish.
  Cons: typically more costly, and some algal products contain mostly DHA with little EPA (check labels). Research shows that algal oils effectively raise blood DHA levels, similar to fish oil.

When choosing a supplement, look at the EPA/DHA content on the label (see tips below). Remember that “1,000 mg fish oil” per capsule may only yield ~300 mg of actual EPA+DHA, so read the fine print on EPA and DHA amounts per dose.

Also note: Cod liver oil is a special fish oil with natural vitamins A and D, but because of its high vitamin A content it should be used cautiously (excess vitamin A can be toxic) and isn’t necessary if you get enough dairy/fortified foods.

Recommended intake and safe dosage

While no official “Recommended Dietary Allowance” (RDA) exists for EPA/DHA specifically, various health organizations give guidance:

• General adult intake: Many experts suggest a minimum of 250–500 mg per day of combined EPA+DHA for overall health. The European Food Safety Authority (EFSA) advises that 250 mg/day is sufficient for maintaining general cardiovascular health. (That’s roughly what you’d get from eating one serving of fatty fish per week.)
• Heart health: The AHA recommends that people without heart disease eat about two fish meals a week. For those with heart disease, the AHA specifically advises ~1 gram per day of EPA+DHA (preferably from fish).
• High triglycerides: To lower very high triglycerides, much higher doses are used. Prescription fish oil drugs typically supply 2–4 grams of EPA/DHA per day under medical supervision, which can significantly cut triglycerides. Over-the-counter supplements at such high doses should only be taken with a doctor’s guidance.
• Pregnancy and infants: Most guidelines recommend pregnant/nursing women eat 8–12 ounces of seafood per week (lower-mercury choices) to support fetal brain and eye development, which provides roughly 200–300 mg DHA daily. Some experts suggest an extra 200–300 mg DHA per day during pregnancy/lactation.

Upper limits and safety: The U.S. FDA considers up to 3,000 mg (3 g) per day of combined EPA+DHA to be safe for the general population. In fact, the FDA’s guideline is to not exceed 3 grams total, of which no more than 2 grams should come from supplements.

Similarly, the EFSA has concluded that intakes up to 5 grams per day do not raise safety concerns for adults. Going beyond these amounts has not been shown to offer extra benefits but can increase risks (see below).

In practice, most people aim for 1–3 grams of EPA+DHA per day via diet and/or supplements, depending on health goals.

Potential risks and side effects

Omega-3s are generally safe, but excessive intake or poor-quality supplements can cause problems. Key points:

• Blood thinning: EPA and DHA have mild blood-thinning effects. At high doses (above ~3 g/day), they can increase bleeding risk. This is why doctors often advise people to stop taking omega-3 supplements 1–2 weeks before surgery. If you are on anticoagulant or antiplatelet medications (e.g. warfarin, aspirin), check with your doctor, as omega-3s can add to the blood-thinning effect. Always consult a healthcare professional before using high-dose omega-3s – especially if you’re considering them for off-label purposes, such as a hangover remedy.
• Vitamin A toxicity: High levels of vitamin A can be dangerous. Some omega-3 supplements like cod liver oil contain a lot of vitamin A, so they should be used cautiously (especially by pregnant women). Regular fish oil or algal oil supplements typically have little or no vitamin A.
• Digestive issues: The most common side effects of fish oil supplements are mild gastrointestinal issues – fishy burps, indigestion, nausea, or diarrhea. Taking supplements with meals or using enteric-coated capsules can minimize these symptoms.
• Rancidity and oxidation: Omega-3 fats are prone to oxidation (going rancid), which can make them not only less effective but potentially harmful. In one study of 171 U.S. supplements, half exceeded voluntary oxidation limits. Rancid fish oil can have a foul smell. To reduce risk, buy reputable brands with antioxidants (like vitamin E) in the oil, and store capsules in a cool, dark place. Discard any supplement that smells off.
• Quality and contaminants: Poor-quality supplements may not contain the EPA/DHA amounts claimed on the label. Independent testing has found that about 30% of products failed to meet label claims. Additionally, very large predatory fish (like swordfish or shark) can contain mercury and other toxins; however, most fish oil supplements are purified and tested for contaminants. Still, it’s safest to choose brands that provide third-party purity testing.

Other interactions: Omega-3s can interact with some medications (e.g. blood thinners, diabetes drugs). If you have a medical condition, discuss omega-3 supplements with your healthcare provider.

Who might especially benefit from omega-3s

While omega-3s are good for almost everyone, certain groups often benefit the most:

• Pregnant or nursing women: As noted, DHA is crucial for fetal brain and eye development. Pregnant women who don’t get enough DHA from their diet can consider a supplement (typically 200–300 mg DHA daily) to support pregnancy outcomes. Low omega-3 status in pregnancy has been linked to higher risk of preterm birth and other complications. Breast milk naturally contains DHA to nourish infants as well.
• Infants and young children: Babies need DHA for brain growth. Many baby formulas include added DHA for this reason. Older children and teens also benefit from omega-3s for cognitive development.
• People with heart disease or high triglycerides: If you have coronary heart disease, heart failure, or very high triglycerides, omega-3 supplements (often prescription-strength) are often recommended alongside medications. Even for those with risk factors (hypertension, obesity), adding omega-3s can help improve lipid profiles.
• Older adults: Age-related cognitive decline and vision loss can be mitigated by healthy diets. Some evidence links higher fish intake with lower dementia risk and higher omega-3 intake with lower risk of macular degeneration. Older people who consume little fish might consider supplements for overall brain and eye support.
• People with mental health concerns: Individuals dealing with depression, anxiety, ADHD or cognitive complaints may try omega-3 supplements (especially higher-EPA formulas) as part of their overall treatment plan, after consulting a doctor.
• Those who eat little or no fish: Vegans, vegetarians or people allergic to fish can use algal oil to get necessary DHA/EPA.
• Overweight or obese individuals: Recent analyses suggest that overweight people may gain more benefit from omega-3 supplements, possibly improving inflammation and metabolic parameters.
• Anyone on a low-ALA diet: If someone’s diet is very low in plant omega-3s (e.g. avoiding nuts/seeds), they might consider ensuring some EPA/DHA intake to make up for it.

Tips for choosing high-quality omega-3 supplements

When shopping for omega-3 supplements, consider these guidelines to ensure safety and potency:

• Consider formulation: Omega-3s come in several chemical forms. Triglyceride (TG), re-esterified TG, and phospholipid forms are well absorbed; ethyl ester (EE) forms are less bioavailable.
  Summarising:
  - Ethyl Ester [EE] – lowest bioavailability
  - Triglyceride [TG] – natural bioavailability
  - re-esterified Triglyceride [rTG] – natural bioavailability
  - Phospholipid [PL] – best bioavailability
• Check EPA/DHA content: The label should clearly list how many milligrams of EPA and DHA each capsule (or teaspoon of liquid) contains. Don’t just look at “fish oil” total. For example, a 1,000 mg fish oil capsule might only provide 300 mg of EPA+DHA combined. Compare products by the actual EPA+DHA dose.
• Look for third-party testing: Choose brands that have been independently tested for purity and potency. Seals from organizations like USP, NSF, or IFOS indicate the product contains what it claims and is free of significant contaminants. Without such testing, one study found only ~70% of omega-3 supplements met label claims.
• Verify freshness: Omega-3 oils easily oxidize. Always check the expiration date and buy products with clear, recent best-by dates. Open a capsule (if possible) to ensure it doesn’t have a strong rancid or fishy odor. Some brands add vitamin E or use nitrogen-flushed packaging to keep oils fresh. Avoid large bulk bottles that may go stale before you finish them. Premium brands provide Certificate of Analysis for specific batches – consider enquiring if the freshness is questionable.
• Check for added ingredients: Some supplements add extra vitamins or other oils. If it’s cod liver oil, be mindful of vitamin A content. If it has other additives, make sure they’re ones you want. A clean list (omega-3s + vitamin E) is often best.
• Sustainability: To minimize environmental impact, look for certifications (like the Marine Stewardship Council – MSC) that the fish were harvested responsibly. Wild-caught small fish (anchovy, sardine) are generally more sustainable than large predators.
• Pick the right type for you: If you prefer capsules, choose softgels with enteric coating to reduce “fish burps.” If you use liquid oil, store it in the fridge and keep it sealed. Vegans/vegetarians should choose algal oil (DHA/EPA) or fermented algal/chia/linseed options rich in ALA.

Always follow the manufacturer’s dosage instructions. Start with the lowest effective dose and adjust as needed (under guidance) for your health goals. And as always, consult your doctor or a registered dietitian if you have specific health conditions or are taking other medications.