Fish Might Be Good For Expecting Mothers

Many pregnant women avoid fish for fear of the mercury content, but a recent study shows that increased fish consumption did not increase mercury levels and does provide for benefits for the baby.

An important part of pregnancy nutrition is ensuring adequate omega-3 fatty acid intake. These types of fats are essential to the development of the brain and nervous system of unborn children, and in turn can improve the outcomes of pregnancy. The best source for omega-3s in the diet is fish, and many nutritionists recommend it for this very reason.

Some people, especially pregnant women, avoid eating fish for fear of mercury. Mercury is a heavy metal that is toxic to human beings, and can be found in particularly high quantities in fatty, long-living fish, exactly the sort you’d want to eat to get enough omega-3s. In fact, as much as ten percent of women of child-bearing age in the United States may have elevated mercury. Because of the conflicting reasons for and against fish consumption a recent study was published in the Nutrition Journal to examine the real risk.

In the study, researchers took pregnant women from the Boston area who didn’t eat much fish already and split them into three groups. One group, as usual, was a control group. Another was a group told to increase their fish consumption, focusing on low-mercury fish that was still high in omega-3s. The third group was the same as the second, but they also received $120 in gift cards and were told to use them to buy fish. Twelve weeks later researchers examined how much fish each group ate, how much omega-3s were consumed, and tested their blood for omega-3s and mercury.

At the outset of the study, none of the women were consuming the recommended amount of omega-3s for pregnancy, which is 200mg per day. At the end of the study, 33% of the women in the advice only group and 53% of the women who received gift cards were meeting the requirement. For both groups that weren’t the control, omega-3 consumption increased quite a bit – almost double for the gift card group.

Ultimately what we learn here is that when someone gives you free money to eat healthy, chances are fifty-fifty you’ll actually do it versus laughing your way to the bank. Just kidding.

On a serious note, the groups had no difference in the mercury content of their blood at the end of the study. The same goes for mercury in the hair, which might be detectable for longer. Interestingly, the omega-3 content of the blood also didn’t change for the groups increasing fish intake. This could be due to a few factors, including a reporting bias, which is a nice way to say the women lied about how much fish they ate, but could have more to do with a general reduction of omega-3s during pregnancy.

It seems that with a focus on healthy fish, concerns over mercury are limited, and the benefits to eating fish are big for all of us, especially pregnant women. Researchers noted that the benefit from eating fish was greater than taking omega-3 supplements. The fish recommend in the study was 6 ounces weekly of salmon, walleye, herring, anchovies and trout, or 12 ounces of Atlantic mackerel, sardines, trout, mussels, Pollock, and salt cod.


1. Emily Oken, et. al., “A pilot randomized controlled trial to promote healthful fish consumption during pregnancy: The Food for Thought Study,” Nutrition Journal 2013, 12:33

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