Fish Oil vs Omega-3: What's the Difference (and Does It Matter?)

People use "fish oil" and "omega-3" interchangeably all the time. Walk into a supplement store and you'll hear it: "I need some omega-3s" while pointing at a bottle of fish oil. And honestly, it's understandable. But they're not the same thing, and the confusion costs people money.

Omega-3 is a nutrient. Fish oil is one way to get it. That distinction sounds small, but it affects everything from what you buy to how much you actually need to take.

Omega-3: The Nutrient You're After

Omega-3 fatty acids are a family of polyunsaturated fats. Three members matter for human health:

• EPA (eicosapentaenoic acid) — primarily anti-inflammatory. Most cardiovascular and mood research focuses on EPA.
• DHA (docosahexaenoic acid) — structural. Makes up about 40% of the polyunsaturated fat in your brain and 60% in the retina of your eye. Critical during pregnancy and early development.
• ALA (alpha-linolenic acid) — plant-based. Found in flaxseed, chia seeds, walnuts. Your body converts ALA to EPA and DHA, but the conversion rate is terrible: roughly 5-10% for EPA and under 5% for DHA.

When researchers study omega-3 benefits — reduced triglycerides, lower inflammation, brain health — they're almost always talking about EPA and DHA specifically. ALA has its own modest benefits, but it's not a reliable replacement.

Fish Oil: Just One Vehicle

Fish oil is extracted from fatty fish like anchovies, sardines, mackerel, and salmon. It contains EPA and DHA, but here's the thing most people miss: standard fish oil is only about 30% omega-3 by weight.

So a "1000 mg fish oil" capsule? It typically delivers just 300 mg of combined EPA and DHA. The remaining 700 mg is other fats — saturated fat, monounsaturated fat, and other fatty acids that aren't doing much for you.

This is the single biggest source of confusion in the omega-3 market, and some brands exploit it deliberately.

The Label Trick You Need to Know

Flip over any fish oil bottle. There are two numbers to look at:

1. Total fish oil per serving (often in large print on the front)
2. EPA + DHA per serving (in the Supplement Facts panel, sometimes in smaller print)

A product screaming "1200 mg Fish Oil!" on the front might only contain 360 mg of EPA+DHA. Meanwhile a concentrated product labeled "720 mg" could deliver exactly 720 mg of EPA+DHA. The second product is actually twice as potent for half the headline number.

Always do the math: price per milligram of EPA+DHA combined. That's the only honest way to compare products.

EPA vs DHA: Which One Matters More?

They do different things, and the ratio in your supplement might matter depending on your goals.

EPA: The Anti-Inflammatory

EPA competes with arachidonic acid (an omega-6 fat) for enzymes that produce inflammatory signals. Higher EPA intake shifts the balance toward less inflammation. Studies on cardiovascular risk reduction — including the large REDUCE-IT trial with 8,179 patients — used high-dose EPA (4 grams/day of icosapent ethyl) and saw a 25% reduction in major cardiovascular events.

EPA also shows up consistently in mood research. A 2019 meta-analysis in Translational Psychiatry found that supplements with 60%+ EPA were effective for depression as an adjunct to medication.

DHA: The Structural Fat

DHA is what your brain is literally made of. Pregnant women need at least 200-300 mg DHA daily for fetal brain and eye development. It's also important for children's cognitive development.

In adults, DHA tends to lower triglycerides more effectively than EPA milligram-for-milligram. It also may slightly raise LDL cholesterol (by a tiny amount), which is something your doctor might mention if your LDL is already high.

For general health, a balanced EPA+DHA supplement works fine. If you're targeting inflammation or mood, lean toward higher EPA. If you're pregnant or focused on brain health, prioritize DHA. — Suppi Research Team

Not Just Fish: Other Omega-3 Sources

Algae Oil

Here's something worth knowing: fish don't actually produce EPA and DHA. They accumulate it by eating algae (or eating smaller fish that ate algae). Algae oil cuts out the middlefish and goes straight to the source.

Algae-derived omega-3 supplements provide meaningful DHA — typically 400-500 mg per serving — and newer formulations include EPA too. Studies confirm that algae-sourced DHA raises blood DHA levels just as effectively as fish oil. It's the only viable option for vegans who want preformed EPA and DHA.

Bonus: no ocean contaminant concerns and no fishy aftertaste.

Krill Oil

Krill oil delivers EPA and DHA bound to phospholipids rather than triglycerides. Some research suggests this form may be absorbed slightly better, but the total amount of omega-3 per capsule is lower — usually 100-150 mg EPA+DHA. You'd need 6-10 krill oil capsules to match what two concentrated fish oil capsules deliver. It also contains astaxanthin, an antioxidant that gives it a red color.

Krill oil is fine if you prefer it, but it's significantly more expensive per milligram of EPA+DHA.

Cod Liver Oil

An old-school option that also provides vitamins A and D. Decent omega-3 content (roughly 900 mg EPA+DHA per tablespoon), but you need to watch the vitamin A — it accumulates, and excessive intake is harmful, especially during pregnancy.

How Much Do You Need?

The American Heart Association recommends:

• General population: Eat fatty fish twice a week (roughly equivalent to 500 mg EPA+DHA daily)
• People with documented heart disease: About 1,000 mg EPA+DHA daily
• People with high triglycerides: 2,000-4,000 mg EPA+DHA daily under medical supervision

Most researchers in the field have settled on 1,000-2,000 mg combined EPA+DHA daily as a reasonable general target. That's not the total fish oil — that's the actual omega-3 content.

With a standard 30% concentration fish oil, you'd need 3-6 capsules per day to hit 1,000-2,000 mg. Concentrated formulas bring that down to 1-2 capsules. The math matters for compliance — nobody enjoys swallowing six horse pills.

The Oxidation Problem

Omega-3 fats are polyunsaturated, which means they oxidize (go rancid) easily when exposed to heat, light, and air. Rancid fish oil doesn't just taste bad — there's growing concern that oxidized omega-3s may be pro-inflammatory rather than anti-inflammatory, potentially negating the whole point of supplementation.

A 2015 study in Scientific Reports tested 32 over-the-counter fish oil products from New Zealand and found that most exceeded recommended oxidation limits. Similar analyses in the US and Europe found comparable problems.

The Burp Test

Cut or bite open a capsule. Fresh fish oil has a mild, slightly oceanic scent. If it smells strongly fishy, metallic, or like old paint, it's oxidized. Persistent fishy burps after taking a capsule are another red flag — fresh fish oil rarely causes them.

Storage Tips

• Keep fish oil in the fridge after opening (even if the label doesn't say to)
• Buy smaller bottles you'll finish within 2-3 months
• Avoid products in clear bottles — light accelerates oxidation
• Check the manufacture or expiration date. Don't buy fish oil that's been sitting on a shelf for a year

Forms of Omega-3: Triglyceride vs Ethyl Ester

Quick note on chemistry, because it affects absorption. Fish oil omega-3s come in two main forms:

• Triglyceride (TG) form: The natural form found in fish. Better absorbed, especially without food.
• Ethyl ester (EE) form: A semi-synthetic form created during concentration/purification. Cheaper to produce, but about 27% less bioavailable than TG form according to a 2011 study in Prostaglandins, Leukotrienes and Essential Fatty Acids.

Most budget fish oil capsules are ethyl esters. Higher-end products reconvert back to triglyceride form after purification — look for "rTG" or "triglyceride form" on the label. If the label doesn't mention the form at all, it's almost certainly ethyl ester.

Safety and Interactions

Fish oil is generally well tolerated up to about 3,000 mg EPA+DHA daily without medical supervision. Above that, you should check with your doctor because:

• Blood thinning: High-dose omega-3 has mild anticoagulant effects. If you're on warfarin, aspirin, or other blood thinners, this interaction matters.
• Surgery: Some surgeons recommend stopping fish oil 1-2 weeks before procedures to reduce bleeding risk.
• Immune suppression: Very high doses may reduce immune function, though this is mostly theoretical at supplemental doses.

Mercury concerns? Reputable fish oil supplements are actually very low in mercury. The distillation process used in manufacturing removes heavy metals effectively. Whole fish (especially large predators like tuna and swordfish) are a much bigger mercury concern than refined fish oil.

What to Actually Buy

Here's a quick decision framework:

• Best value: Concentrated fish oil in triglyceride form, 500+ mg EPA+DHA per capsule
• Best for vegans: Algae oil with both DHA and EPA
• Best for people who hate pills: Liquid fish oil (lemon-flavored options taste surprisingly decent) or small-capsule krill oil
• What to skip: Anything that only lists total fish oil and hides the EPA+DHA numbers

Look for third-party testing from IFOS (International Fish Oil Standards), NSF, or USP. These verify both omega-3 content and oxidation levels.

1. Bhatt DL, et al. "Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia." REDUCE-IT Trial. N Engl J Med. 2019;380(1):11-22.
2. Liao Y, et al. "Efficacy of omega-3 PUFAs in depression: A meta-analysis." Translational Psychiatry. 2019;9:190.
3. Albert BB, et al. "Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA." Scientific Reports. 2015;5:7928.
4. Dyerberg J, et al. "Bioavailability of marine n-3 fatty acid formulations." Prostaglandins Leukot Essent Fatty Acids. 2010;83(3):137-141.
5. American Heart Association. "Fish and Omega-3 Fatty Acids." Recommendations for Fish Consumption. Updated 2024.
6. Arterburn LM, et al. "Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid." J Am Diet Assoc. 2008;108(7):1204-9.