discussvegan.

Don't you need fish for brain DHA, especially in pregnancy?

Short answer: You need DHA, not fish. Algae oil (where fish get theirs) raises blood DHA as effectively, without the mercury. A sensible choice in pregnancy.

Exhibit A
Fish vs the actual source

Geppert et al. (2006); Craddock et al. (2017)

The objection

“DHA is critical for the developing brain. Vegans skip fish, so their babies miss out, this one really matters.”

The answer

This deserves to be taken seriously, so here goes. DHA is genuinely critical, a structural fat in the brain and retina, laid down fastest in the third trimester and infancy. And the conversion route plants offer is weak: the body turns the plant omega-3 ALA (flax, chia, walnuts) into DHA at only a few percent, often near-zero in men. “Just eat flaxseed and you’re fine” would be overclaiming, so we won’t say it.

Where the objection goes wrong is the equation DHA = fish. Fish don’t make DHA. Algae do. Fish are simply the tank that concentrates it, along with the mercury, PCBs and microplastics that come with eating up the food chain. Skip the fish and go straight to the source with algae-oil supplements. Controlled trials show algal DHA raises plasma and red-cell DHA in vegetarians comparably to fish oil. It’s the same molecule.

For pregnancy and breastfeeding the practical answer is simple: take a direct algae-derived DHA supplement (commonly ~200–300 mg/day), exactly as non-fish-eating omnivores are often advised to. That sidesteps the contaminant load fish carry, which is a real consideration when oily-fish intake in pregnancy is capped precisely because of mercury.

DHA matters too much to leave to chance on any diet, vegan or not. The sensible move is to supplement it directly from the organism fish got it from in the first place, and skip the fish.

Sources

  1. Craddock et al., Algal supplementation of vegetarian eating patterns improves plasma and serum DHA, J Hum Nutr Diet (2017)
  2. Geppert et al., Microalgal docosahexaenoic acid decreases plasma triacylglycerol in vegetarians, Br J Nutr (2006)
  3. Cao et al., Vegetarian/vegan diet and omega-3 status, review of algal oil as a DHA source, Front Nutr (2024)