Omega-3s from food vs. supplements: what actually matters

"Omega-3" is a marketing umbrella that hides an important distinction: there are three relevant omega-3 fatty acids, and your body uses them differently.

The three omega-3s

EPA (eicosapentaenoic acid). Found in fatty fish and fish oil. Anti-inflammatory effects, cardiovascular benefits.

DHA (docosahexaenoic acid). Found in fatty fish, fish oil, algae oil. Critical for brain and eye health, especially in pregnancy and infancy.

ALA (alpha-linolenic acid). Found in flax, chia, walnuts, hemp. The plant-source omega-3.

The catch: ALA has to be converted to EPA and DHA in the body to do most of the things "omega-3s are good for" implies. The conversion rate is poor — about 5–10% to EPA and 0.5% to DHA in healthy adults.

This is the central nutrition fact most "omega-3s are good for you" advice glosses over.

What this means in practice

If you eat fatty fish 2x a week, you're probably getting adequate EPA + DHA from food. The American Heart Association recommends ~250–500mg EPA + DHA daily; one 6oz serving of salmon is ~2,000mg. Two servings a week is more than enough.

If you don't eat fatty fish, your dietary EPA + DHA is essentially zero. Walnuts and flax give you ALA, but the conversion is too inefficient to count on. You either need to start eating fatty fish or supplement.

Supplement basics

Fish oil supplements come in two main forms:

• Triglyceride form. Closer to natural fish oil, better absorption, slightly more expensive.
• Ethyl ester form. Cheaper, requires food (especially fat) for good absorption, often the cheaper drugstore brands.

For dose: aim for 1,000mg combined EPA + DHA per day if you're a non-fish-eater. Look for "EPA + DHA per serving" — not "fish oil per serving" — on the label. A 1,000mg fish oil capsule often contains only 300mg of EPA + DHA.

Algae oil for vegans

Algae oil is the only vegan source of pre-formed EPA + DHA. Brands: Nordic Naturals Algae, Ovega-3, Testa. Doses run 300–500mg per softgel. Slightly more expensive per gram than fish oil but identical biological activity.

The fish oil rancidity problem

Fish oil oxidizes easily. Rancid fish oil is at best useless and at worst pro-inflammatory. Signs of rancidity: strong fishy smell when you crack a capsule, fishy burps for hours after taking, a darkened oil color in the bottle.

Buy fish oil from a brand with third-party testing (IFOS certification is the gold standard). Refrigerate after opening. Don't buy bulk Costco-size bottles unless you'll finish them in 60 days.

Who actually needs this

• People who don't eat fatty fish 2x a week
• Pregnant or breastfeeding women (DHA for fetal brain development)
• People with elevated triglycerides (high-dose EPA has prescription evidence)
• Vegans / vegetarians (almost certainly low; algae oil is the fix)
• Anyone with diagnosed inflammatory conditions where their physician has recommended it

Who probably doesn't

• Mediterranean-style eaters
• People who eat sardines / anchovies / salmon regularly
• People taking blood thinners without medical guidance (high-dose fish oil can interact)

The bottom line

The "omega-3s are healthy" headline is true. The fix isn't ALA-rich foods unless you're eating massive quantities. For most non-fish-eaters, a 1,000mg EPA+DHA supplement is the cheapest, most evidence-backed thing you can do for your cardiovascular and cognitive health.

ALA is fine. EPA and DHA are the ones the trials are about.