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Seafood Can Boost Children’s IQ, Despite Possible Mercury Exposure

Seafood Can Boost Children’s IQ, Despite Possible Mercury Exposure


Women who eat seafood while pregnant may be boosting their children’s IQ in the process, according to new research published Friday in The Lancet.

The study relied on mothers’ observations of their children’s development and their reports of their food intake while pregnant. The study, led by Dr. Joseph Hibbeln of the United States’ National Institutes of Health, tracked the eating habits of 11,875 pregnant women in Bristol, Britain.

Smarter kids?
At 32 weeks into their pregnancy, the women were asked to fill in a seafood consumption questionnaire. They were subsequently sent questionnaires four times during their pregnancy, and then up to eight years after the birth of their child. Researchers examined issues including the children’s social and communication skills, their hand-eye coordination, and their IQ levels. As with any study based on self-reporting methods, however, the results cannot be considered entirely definitive.

Women who ate more than 340 grams per week of fish or seafood, the equivalent of two or three servings a week, had smarter children with better developmental skills. Children whose mothers ate no seafood were 48% more likely to have a low verbal IQ scores, compared to children whose mothers ate high amounts of seafood.

“These results highlight the importance of including fish in the maternal diet and lend support to the popular opinion that fish is brain food,” wrote Dr. Gary Myers and Dr. Philip Davidson of the University of Rochester Medical Center, in an accompanying commentary. Myers and Davidson were not connected to the study.

Pollution worries
The Environmental Working Group, which calls the U.S. recommendations too lenient, said the study highlighted the need for governments to take actions to keep pollutants out of seafood, like cracking down on coal-burning power plants.

“The study reinforces the importance of keeping our seafood supply clean, making sure it’s not overly contaminated with mercury and other chemicals that could actually harm brain development,” said Jane Houlihan, the group’s vice president for research.

Mercury can build up in fish living in waters contaminated with it due to industrial pollution. Mercury can be particularly bad for fetuses and children because it can cause neurological and developmental problems.

In 2004, the U.S. Environmental Protection Agency and Food and Drug Administration advised pregnant women and young children to eat no more than 12 ounces per week of light tuna and other seafood lower in mercury.

The agencies recommended they eating fish with high mercury levels – shark, swordfish, king mackerel and tilefish – and no more than 6 ounces (170 grams) a week of albacore tuna because of mercury.


Fish is a very important part of a Nutrient Dense Fertility Diet. If you are not eating fish because of fear of mercury poisoning, you are throwing the baby out with the bath water. There are certain fish that are known to be high in mercury.

What about mercury?
Mercury is definitely a concern, but there are fish you can eat that are lower in mercury due to their location and what they eat. I would be more concerned about the mercury poisoning from dental fillings. They are constantly leaking mercury in to your system every time you chew, eat hot foods, etc. So fish is good, just be smart about which ones you eat. Canned tuna is out. Here is the Consumer’s Guide to Mercury in Fish provided by the Natural Resources Defense Council.

You can download a printable fish safety card to put in your wallet for access when at restaurants or shopping.

Consumer Guide to Mercury in Fish

The list below shows the amount of various types of fish that a woman who is pregnant or planning to become pregnant can safely eat, according to the Environmental Protection Agency. People with small children who want to use the list as a guide should reduce portion sizes. Adult men and women who are not planning to become pregnant are less at risk from mercury exposure but may wish to refer to the list for low-mercury choices.

Protecting yourself — and the fish: Certain fish, even some that are low in mercury, make poor choices for other reasons, most often because they have been fished so extensively that their numbers are perilously low. These fish are marked with an asterisk (read more below).

Least Mercury
Enjoy these fish:
Crab (Domestic)
Croaker (Atlantic)
Haddock (Atlantic)*
Mackerel (N. Atlantic, Chub)
Perch (Ocean)
Salmon (Canned)**
Salmon (Fresh)**
Shad (American)
Sole (Pacific)
Squid (Calamari)
Trout (Freshwater)
Moderate Mercury
Eat six servings or less per month:
Bass (Striped, Black)
Cod (Alaskan)*
Croaker (White Pacific)
Halibut (Atlantic)*
Halibut (Pacific)
Mahi Mahi
Perch (Freshwater)
Tuna (Canned
chunk light)
Tuna (Skipjack)*
Weakfish (Sea Trout)
High Mercury
Eat three servings or less per month:
Mackerel (Spanish, Gulf)
Sea Bass (Chilean)*
Tuna (Canned Albacore)
Tuna (Yellowfin)*
Highest Mercury
Avoid eating:
Mackerel (King)
Orange Roughy*
Tuna (Bigeye, Ahi)*

* Fish in Trouble! These fish are perilously low in numbers or are caught using environmentally destructive methods. To learn more, see the Monterey Bay Aquarium and the Blue Ocean Institute, both of which provide guides to fish to enjoy or avoid on the basis of environmental factors.

** Farmed Salmon may contain PCB’s, chemicals with serious long-term health effects.

Sources for NRDC’s guide: The data for this guide to mercury in fish comes from two federal agencies: The Food and Drug Administration, which tests fish for mercury, and the Environmental Protection Agency, which determines mercury levels that it considers safe for women of childbearing age.

About the mercury-level categories: The categories on the list (least mercury to highest mercury) are determined according to the following mercury levels in the flesh of tested fish.

    Least mercury: Less than 0.09 parts per million
    Moderate mercury: From 0.09 to 0.29 parts per million
    High mercury: From 0.3 to 0.49 parts per million
    Highest mercury: More than .5 parts per million

Favorite Fish Recipe

Thai Coconut Salmon
1 can coconut milk
1 lemon
2 strands saffron
1 stalk lemon grass
1t. arrowroot
1T. fish sauce
2-4 fillets of Wild Alaskan Salmon (not farm raised)

    1.Pour coconut milk into a sauce pan
    2.Cut some big pieces of lemon skin (zest). Add to the coconut milk.
    3.Cut lemon grass 5-inch pieces, add with saffron to the coconut milk.
    4.Heat for simmer for 8 min.
    5.Meanwhile juice the lemon and dissolve the arrowroot.
    6.Add the fish sauce (stinky, but will taste awesome ;), simmer another 5 min.
    7.Remove the large lemon peels and lemongrass from coconut milk
    8.Place salmon fillets in the simmering sauce. Cover and cook for 5-10 minutes, until pale pink all the way through
    9.Put salmon onto plates
    10.Whisk the lemon/arrowroot mixture into the coconut milk. It should thicken instantly. Taste sauce, season and add to the top of the salmon.

This meal would go great served with some quinoa and asparagus.
Bon appetit

Dr. Christine Traxler M.D., OB/GYN
Dr. Christine Traxler M.D., OB/GYN

Dr. Traxler is a University-trained obstetrician/gynecologist, working with patients in Minnesota for over 20 years. She is a professional medical writer; having authored multiple books on pregnancy and childbirth; textbooks and coursework for medical students and other healthcare providers; and has written over 1000 articles on medical, health, and wellness topics.  Dr. Traxler attended the University of Minnesota College of Biological Sciences and University of Minnesota Medical School,  earning a degree in biochemistry with summa cum laude honors in 1981,  and receiving her Medical Doctorate degree (MD) in 1986.

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