Omega-3 without fish

Vegan and vegetarian omega-3 strategies need a different game plan. ALA conversion is poor, and the body can't make meaningful amounts of DHA from plants alone — with one important exception: algae.

The conversion problem

The body can convert the plant omega-3 ALA into EPA and DHA, but the rates are low. Brenna et al. (2009, Prostaglandins, Leukotrienes & Essential Fatty Acids) reviewed the evidence and concluded ALA → EPA conversion sits at roughly 5–10% in healthy adults. ALA → DHA conversion is <1%, and often essentially zero in men.

Women convert slightly better thanks to oestrogen-mediated FADS enzyme activity (Burdge & Wootton, 2002, British Journal of Nutrition). The practical implication: eating lots of flaxseed, chia or walnuts gives you plenty of ALA — but only a small fraction becomes the EPA and DHA your body actually uses.

ALA-rich plant foods (still worth eating)

Food	Serving	ALA
Flaxseed (ground)	1 tbsp · 7 g	~1,600 mg
Chia seeds	1 tbsp · 14 g	~2,500 mg
Walnuts	28 g · handful	~2,600 mg
Hemp seeds	1 tbsp · 10 g	~900 mg

At a 5% conversion rate, 2,500 mg of ALA yields roughly 125 mg EPA. Useful — but you'd need a substantial daily intake of seeds to hit a 1,000+ mg/day EPA+DHA target on plants alone.

Algae-based EPA + DHA (the headline solution)

DHA is made by marine microalgae. Fish only contain DHA because they eat algae — or eat fish that ate algae. Algae oil supplements give you DHA, and increasingly EPA, directly — skipping the fish entirely.

Look for products listing both EPA and DHA. Older algae products were DHA-only; newer strains (Schizochytrium sp., Crypthecodinium cohnii) yield both.
Typical dose per capsule: 250–500 mg DHA, sometimes paired with 100–200 mg EPA. Higher-end products provide 500 mg combined EPA+DHA per capsule.
To hit ~1,000–1,500 mg/day, expect to take 2–3 capsules daily.
Bioequivalent to fish-derived DHA for raising the Omega-3 Index (Arterburn et al. 2008, Journal of the American Dietetic Association).

Krill oil

Not vegan, but worth covering. Krill oil is marine-sourced from krill (small crustaceans). The fatty acids come in phospholipid form, which some studies (Ramprasath 2013; Schuchardt 2011) suggest absorbs slightly better per milligram than triglyceride fish oil. It also includes the antioxidant astaxanthin.

The catch: EPA+DHA content per capsule is typically lower (~120–190 mg total), so you need more capsules to reach the same dose.

Practical vegan strategy

Daily diet base: 1–2 tbsp ground flaxseed plus 1 tbsp chia (roughly 4,000 mg ALA, which translates to a small EPA contribution after conversion).
Plus: an algae oil supplement providing 500–1,000 mg combined EPA+DHA per day.
Total dietary EPA+DHA target: 800–1,500 mg/day.
Retest your Omega-3 Index after 4 months. You may need to adjust the dose based on where you land.

What about seaweed?

Most edible seaweed — nori, wakame, dulse — is very low in EPA and DHA. Algae oil supplements are far more concentrated than any whole seaweed. Don't expect to hit your target from seaweed in the diet alone.