Eating Fish while Pregnant: What We Do and Don’t Know
This article started out trying to put together a chart, similar to the one below by the US’ Food and Drug Administration, to advise women which Indian fish are best for pregnant women and in what quantities. It ended in defeat; we couldn’t create such recommendations because the data doesn’t exist (or isn’t shared). What we can tell you, however, are the pros and cons of eating fish while pregnant, and there are plenty of both.
First, a quick lesson in biology. Fish naturally contain nutrients critical to building fetal neurons and cell membranes. These omega-3 fatty acids, called DHA and EPA, are difficult to find in other foods.
However, fish also absorb mercury from their environment faster than they can cleanse it from their bodies. Therefore, they can build up high levels of mercury simply by eating normally. Bigger fish (which eat the smaller fish) tend to have the highest levels of mercury, but mercury levels in fish also depend on what environment they live and eat in.
Mercury in fish in India
Mercury contamination in fish is a huge problem in India, according to Satish Sinha, associate director of ToxicsLink, an environmental NGO, and the government does not track it or issue recommendations to consumers. In 2010, ToxicsLink co-published a report with DISHA, similar organization, which found nearly half of popular varieties of fish sampled in West Bengal contained methyl mercury levels above Prevention of Food Adulteration standards.
However, Sinha said, the fact that the chlor-alkali sector, a major source of contamination, switched to mercury-free technology several years ago suggests mercury contamination may have decreased, though he stopped short of guessing by how much.
Which leaves pregnant women guessing instead – not fun when a baby’s healthy development is at stake.
Or is it? For years, Western obstetric advice has sought to limit – though not eliminate – fish intake because of the exposure of mercury to the fetus. (Among other things, high levels can stymie brain development.) But the Eastern half of the globe – where fish is a much larger part of diets – has remained relatively unconcerned; pregnant women in Japan, for instance, eat sushi throughout their pregnancies, with no limits advised. And a recent study muddies the waters further.
Should pregnant women eat fish?
Published in the American Journal of Epidemiology, 2,000 pregnant women were asked to report their weekly fish intake via questionnaire. At birth, their umbilical cord blood was tested for mercury levels and DHA levels. Afterward, their children were tested at 14 months for cognitive ability and signs of autism spectrum disorder, and again at age 5.
The study found eating 600 grams (roughly three to four servings) of fish each week of pregnancy was linked to a 2.8 point boost in children’s IQ. But most intriguing was the fact that the children of women who ate large fatty fish (which have the most DHA, but also the most mercury), like tuna, didn’t display neurodevelopmental problems, as expected. Those mothers’ cord blood had higher amounts of both DHA and mercury, but their children didn’t have a higher incidence of developmental issues.
“Overall, the present results suggest no adverse associations of high seafood consumption in pregnancy with offspring neurodevelopment,” the study authors wrote.
However, fish every day doesn’t seem to be a good idea either; the study found the neural benefits for children tapered off when pregnant women ate more than three to four servings of fish a week.
While the study is far from conclusive – it was designed to be observational, not look for a cause – it suggests a happier medium between Eastern and Western diets might be the best guide when it comes to eating fish during pregnancy and ensuring your baby gets the nutrients he needs, with as little toxins as possible. (For now — another recent study has also suggested climate change will increase mercury levels in fish, so watch the site for future updates.)