Omega-3 Food Sources: Milligrams Per Serving

Two numbers on the tables below look similar and mean different things. A tablespoon of ground flaxseed carries about 1,600 mg of omega-3; a 3.5-ounce portion of sardines carries about 980 mg. The sardines win, because the flaxseed number is all ALA and the sardine number is all EPA and DHA.

Seafood, EPA plus DHA per 3.5-ounce (100 g) cooked portion

Values from USDA nutrient data as compiled in the National Academies seafood report. Actual content swings with species, feed and preparation, so read these as the middle of a range.

Food	EPA + DHA
Atlantic salmon, farmed, cooked	2,150 mg
Atlantic sardines, canned in oil, drained, with bone	980 mg
White (albacore) tuna, canned in water, drained	860 mg
Alaska pollock, cooked	510 mg
Shrimp, cooked	280 mg
Atlantic cod, cooked	160 mg
Tilapia, cooked	135 mg

The spread across that column is roughly sixteenfold, which is the single most useful fact on this page. “Eat fish” and “eat oily fish” are different instructions: tilapia and cod are excellent protein and near-irrelevant as omega-3 sources, while one salmon fillet covers a week.

Salmon carries a second bonus the table does not show. The same report names it the fish with the highest vitamin D concentration, above 13 micrograms per 100 grams — relevant if you are also weighing vitamin D from sun against vitamin D from food.

Plants, ALA per usual serving

Values from USDA FoodData Central, per the serving weights the database itself lists.

Food	Serving	ALA
Chia seeds, dried	1 oz (28 g)	5,000 mg
English walnuts	1 oz, 14 halves (28 g)	2,570 mg
Ground flaxseed	1 tbsp (7 g)	1,600 mg

Every figure in that table is larger than most of the seafood figures above, and that is exactly the trap. ALA has to be elongated and desaturated before the body can use it as EPA or DHA, and the National Academies put that conversion at under 10 percent — the DHA step lower still. The 5,000 mg from an ounce of chia does not arrive as 5,000 mg of usable marine omega-3, and no serving size fixes that.

What plants do give you is real: ALA is the one omega-3 with a US reference value, an Adequate Intake of 1.6 g a day for men and 1.1 g for women, and a single tablespoon of flaxseed covers most of it. The difference between covering ALA and covering EPA and DHA is the whole subject of EPA versus DHA.

Building a week instead of a day

Nothing here needs to happen daily. Two 3.5-ounce servings of oily fish across a week — the American Heart Association’s advice as MedlinePlus states it — average out well past any published EPA and DHA target, which is why daily omega-3 recommendations are best treated as weekly arithmetic.

A workable pattern: sardines or canned salmon on a weekday, a salmon or trout fillet at the weekend, and seeds or nuts wherever they fit. If fish is off the menu entirely, the plant column alone will not close the gap and vegan omega-3 sources covers what does.

This content is informational and does not replace individual dietetic advice.