This article is an excerpt from the Shortform summary of "Expecting Better" by Emily Oster. Shortform has the world's best summaries of books you should be reading.
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You’ve heard that fish is good during pregnancy. But are all fish created equal? Which are the best fish for pregnancy? Is tuna good, or is it harmful?
Learn all about eating fish while pregnancy here.
What Makes for Good Fish During Pregnancy?
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 While Pregnant
Here’s a nifty fish chart from Expecting Better, showing fish on a graph with the two criteria we just talked about: omega-3’s, and mercury level.
The best fish to eat are: salmon, herring, sardines, pollock, and mackerel. These have high omega-3’s, while containing low mercury.
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.
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Here's what you'll find in our full Expecting Better summary :
- Why much parenting advice you hear is confusing or nonsense
- The most reliable way to conceive successfully
- How much alcohol research shows you can drink safely while pregnant (it's more than zero)
- The best foods to eat, and what foods you really should avoid
