Which fish are best for you to eat during pregnancy? In Expecting Better, Emily Oster covers the best fish while pregnant, from best to worst.
First, let’s review. Fish have two competing effects on the fetus:
- High mercury lowers IQ.
- A 1 ug/g increase in mercury sampling causes a decrease of 0.7 IQ points. In other words, the average American woman and the highest mercury-exposed woman produces a 3.5 IQ point difference in kids.
- Predator fish and long-living fish (listed below) have the highest levels of mercury. The former eats other fish harboring mercury, and the latter accumulates mercury over a long lifetime.
- Omega-3 fatty acids increase IQ.
- Increasing DHA fatty acids by 1 g/day would increase IQ by 1.3 points.
The solution is to eat high omega-3 fish with low mercury. The best fish to eat are: salmon, herring, sardines, pollock, and mackerel.
Here’s a nifty fish chart from Expecting Better:
The worst fish to absolutely AVOID are: orange roughy, canned tuna, king mackerel, grouper, shark, swordfish. These contain low omega-3 but have high mercury.
The fish you should avoid for reasons of high mercury are: swordfish, shark, sushi-grade tuna, halibut, tilefish. Even though these contain more omega-3s than the fish in the last list, they contain more mercury than they’re worth.
Finally, these fish are somewhere in the middle: tilefish, halibut, sushi-grade tuna, flounder snapper, catfish, cod. They have acceptable levels of omega-3 and mercury, but there are better fish out there to focus on, like salmon and sardines.