Between the changing body, wacky hormones and mommy brain, being pregnant is stressful enough. Pregnancy nutrition is important, but we don’t want it to be confusing. Fresh fruits and veggies are obvious picks. Seafood, on the other hand, is a trickier subject.
Is it okay to eat seafood when you’re growing a babe? Guest blogger, Dr. Nicholas Ralston, helps us answer this age-old question.
Ocean fish are rich in omega-3 fatty acids, selenium, vitamin D, vitamin E and iodine. For this reason, the FDA recommends pregnant women eat up to 12 ounces of low-mercury seafood per week, an amount equal to two portions that are about the size of a woman’s palm.
Studies have found that children whose mothers ate more ocean fish did better on intelligence tests and have greater social and scholastic aptitudes than children whose mothers ate less than two fish meals per week. Children whose mothers ate no fish did the poorest.
What about the mercury?
Current warnings regarding mercury risks arose after negative effects reported in a Faroe Islands study. The Faroe Islands lie between Iceland and Scotland. Because their mercury exposures are among the highest worldwide, this population was one of the first studied. However, only a fraction of their mercury exposure comes from eating fish. The majority of their mercury exposure comes from eating pilot whale meat.
Pilot whales are slightly smaller than their killer whale cousins. Mercury exposures from pilot whales and large sharks can be harmful, but beneficial effects are observed in children whose mothers eat more commonly consumed ocean fish. The difference depends on how much mercury is in relation to the amount of selenium.
Selenium’s role in preventing mercury toxicity was first shown in 1967 and has been under continual study since. In fact, to understand any aspect of the seafood mercury issue, you must first understand selenium’s role in the body and the interactions between mercury and selenium.
What is selenium?
Selenium is an essential trace element that we need in our diets for numerous processes, including brain development and protection from oxidative damage. A pregnant mother needs to supply selenium to her baby in order to meet the needs of her child’s growing brain.
Under normal conditions, selenium is effectively delivered from the mother to her baby. However, high mercury exposure directly interferes with this process. We now know the way mercury causes harm is by binding selenium and preventing it from performing its necessary functions.
The Basic Chemistry
Since one atom of mercury binds one atom of selenium, it is important to eat foods that contain more selenium than mercury. Virtually all foods (including almost all seafoods) contain much more selenium than mercury. The only seafoods that contain significantly more mercury are pilot whale and shark meats. (These are the mercury-containing foods that were the basis for the fish consumption advisories.)
In the Faroes study, the more ocean fish that mothers ate during pregnancy, the better protected their children were from the bad effects of eating whale meat. This is because ocean fish are rich in selenium.
So, our best advice? Eat up to two 6 ounce servings of low-mercury fish per week. You’ll be providing essential nutrients for yourself and your baby, and possibly boosting your baby’s cognitive development. In other words, go fish.
What is your favorite fish dish? Let us know.
Dr. Nicholas Ralston worked in nutrition research for many years and was trained in biomedical research at the Mayo Graduate School, Rochester, Minn. For the past 12 years, he has led dozens of research studies of mercury–selenium interactions that have been primarily funded by the National Oceanic and Atmospheric Administration and the U.S. Environmental Protection Agency.