For an expectant parent, keeping up with the list of recommended dos and don’ts of pregnancy can be overwhelming. Take multivitamins. Get plenty of sleep. Even…stop cleaning the cat box. (If you hadn’t heard that last one, Google the terrifying terms “cat litter toxoplasmosis.” You may need a stiff drink afterward, but don’t do that, either.)
When it comes to nutrition, the advice gets even more insistent, and often confusing. But it does boil down to the simple truth that growing bodies depend on a number of vital nutrients to develop properly. And when you’re pregnant, your body needs more of certain nutrients, including iron, folic acid, calcium, and iodine (ODPHP, 2020). The fetus needs to suck up nutrient-rich foods packed with healthy fats, lean proteins, and vitamins.
There are some obvious sources to turn to for these nutrients. Dairy provides calcium and protein. Broccoli and leafy greens like kale and spinach are rich in iron, potassium, fiber, and a number of vitamins. Legumes are packed with folate. And sweet potatoes are loaded with beta carotene that your body can turn into vitamin A (OWH 2020).
But there’s one dietary recommendation that’s drawn more public attention and academic research over the years than almost any other. Should pregnant mothers eat fish, or is mercury too great a concern?
For over a decade, scientific research has found the answer to be a consistent “yes” to fish, even if the level of public knowledge on the issue hasn’t caught up. The omega-3 fatty acids found in seafood are essential for healthy pregnancies, babies, and children (Innis, 2008). These vital nutrients are important for a baby’s eyes, brains, and immune system. On that basis, the Food and Drug Administration recommends pregnant mothers eat fish a couple times each week (FDA, 2020).
While mercury can be a concern for certain kinds of large predators, such as shark and swordfish (which are relatively rarely eaten in the U.S.), other species contain little mercury. And in general, the benefits of eating seafood far outweigh the risks.
Moms Should Eat More Seafood
Back in 2007, a study from the U.K. found that mothers who ate more seafood when pregnant had children who performed better on intelligence tests and had better social and speaking skills — even improved physical dexterity (Hibbeln, 2007). Notably, the mothers examined in the study, dubbed "Children of the 90s,” had actually eaten more seafood than the weekly 12 ounces — the equivalent of eating seafood two or three times in a given week — that U.S. officials recommend. In exceeding 12 ounces, these mothers had gotten a true abundance of omega-3 fatty acids.
Interestingly, the team also found no evidence to support warnings for pregnant mothers about mercury (Hibbeln, 2007). On the contrary, the researchers concluded that advising pregnant mothers to avoid seafood could be detrimental to their child’s long-term health.
“We've assessed the advisory, and we've concluded that the advisory causes the harm it intended to prevent,” Capt. Joseph Hibbeln of the National Institutes of Health’s Laboratory of Membrane Biochemistry and Biophysics told Newsweek at the time.
The human body can’t make omega-3 on its own, we have to get these nutrients from our food. And plants and even land animals don’t have the most beneficial kinds of omega-3 fatty acids. Only seafood, such as wild-caught salmon, can provide EPA and DHA, two omega-3s that are vital for brain and body development (McNamara et al., 2006.) So, if you’re not eating enough seafood, or you’re not taking an omega-3 supplement, you’re not getting ample omega-3. (Ryan et al., 2010).
And in 2014, the FDA revised its guidelines to increase the recommended amount of fish Americans should eat (FDA 2014). That change was based on years of scientific study showing that moms and kids who eat more fish see health benefits.
In the latest dietary guidelines published in December 2020, the U.S. Food and Drug Administration recommends that pregnant mothers eat eight to 12 ounces of fish each week. Further, the FDA breaks fish down into three different categories based on their mercury levels with specific recommended weekly servings for each.
Choose the Best
The FDA recommends eating two or three weekly servings of fish from its “best choices” category, which includes salmon, cod, sardines, scallops, shrimp, mackerel, and more. These mostly short-lived fish accumulate very little mercury in their bodies. They also say that it’s OK to eat one serving per week from the "good choices" category, like halibut, Chilean sea bass, and a number of kinds of fresh tuna. Meanwhile, the FDA suggests avoiding marlin, shark, swordfish, and several other very long-lived fish, like orange roughy, which can live for centuries. These kinds of fish typically have the highest levels of mercury
And their advice also emphasizes the importance of eating fish. “Fish and other protein-rich foods have nutrients that can help your child's growth and development,” the FDA says. “As part of a healthy eating pattern, eating fish may also offer heart health benefits and lower the risk of obesity.”
Specifically, the FDA calls out seafood for its protein and healthy omega-3 fats, as well as minerals such as selenium, zinc, and iodine. They also say that seafood boasts more vitamin B12 and vitamin D than any other type of food. These vitamins are important for a developing baby’s brain and spine, according to the American Pregnancy Association. Finally, the FDA suggests pregnant mothers should eat fish because it’s an excellent source of iron. Like omega-3 fatty acids, iron is important for pregnant moms and women who could become pregnant. A woman’s body needs that iron as it makes blood to supply oxygen to a fetus.
Why Is There Mercury in Fish?
So, if there are so many strong reasons for expectant mothers to eat fish, why did mercury warnings work their way into seafood recommendations in the first place?
Mercury exists naturally in the ocean, making its way into the water in small amounts from volcanic vents on the ocean floor and other geological processes. Industrial waste and coal burning can also add mercury pollution to the ocean. Most fish aren’t ever exposed to enough mercury to harm humans. However, large predatory ocean fish — like some deep-dwelling tuna species — spend years eating smaller fish, which means mercury can “bioaccumulate” in their bodies.
Where omega-3 is a brain-booster, mercury can stop neurons from finding their proper places in the developing brains of babies and young children. That’s why medical officials recommend eating chunk light tuna, which comes from skipjack, a smaller species. Learn more about the unique ways in which Vital Choice sources its premium tuna.
In general, small, wild-caught fish have the lowest levels of mercury, which makes them a great choice for expectant mothers. That means that adding fish like sardines, anchovies or even mackerel is a great way to get in necessary nutrients. And the FDA guidelines include dozens of other “best choice” fish to choose from, including salmon.
So, even after accounting for larger fish with mercury concerns, you’re still left with a significant seafood menu to choose from and add an omega-3 boost to your meal. Now you can move on to worrying about deli meat, how much caffeine is really too much, and why the rest of the family is ignoring Fluffy’s overflowing litter box.
U.S. Department of Health and Human Services. Office of Disease Prevention and Health Promotion. Eat Healthy During Pregnancy: Quick tips. Updated October 2020. https://health.gov/myhealthfinder/topics/pregnancy/nutrition-and-physical-activity/eat-healthy-during-pregnancy-quick-tips
U.S. Department of Health and Human Services. Office on Women's Health. You’re Pregnant, Now What? Staying Healthy and Safe. March 2019. https://www.womenshealth.gov/pregnancy/youre-pregnant-now-what/staying-healthy-and-safe?_ga=2.246471500.953293817.1610678653-355494257.1610678653
Innis SM. Dietary omega 3 fatty acids and the developing brain. Brain Res. 2008 Oct 27;1237:35-43. doi: 10.1016/j.brainres.2008.08.078. Epub 2008 Sep 9. Review.
U.S. Food and Drug Administration (FDA). Advice About Eating Fish For Women Who Are or Might Become Pregnant, Breastfeeding Mothers, and Young Children December 2020. https://www.fda.gov/food/consumers/advice-about-eating-fish
Hibbeln JR, Davis JM, Steer C, Emmett P, Rogers I, Williams C, Golding J. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. Lancet. 2007 Feb 17;369(9561):578-85.
U.S. Food and Drug Administration (FDA). New Advice: Pregnant Women and Young Children Should Eat More Fish. 2014. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm397443.htm
U.S. Food and Drug Administration (FDA). Fish: What Pregnant Women and Parents Should Know: Draft Updated Advice by FDA and EPA. http://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm
U.S. Food and Drug Administration (FDA). Report of Quantitative Risk and Benefit Assessment of Consumption of Commercial Fish, Focusing on Fetal Neurodevelopment Effects (Measured by Verbal Development in Children) and on Coronary Heart Disease and Stroke in the General Population http://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm088794.htm
McNamara RK, Carlson SE. Role of omega-3 fatty acids in brain development and function: potential implications for the pathogenesis and prevention of psychopathology. Prostaglandins Leukot Essent Fatty Acids. 2006 Oct-Nov;75(4-5):329-49. Epub 2006 Sep 1. Review.
Ryan AS, Astwood JD, Gautier S, Kuratko CN, Nelson EB, Salem N Jr. Effects of long-chain polyunsaturated fatty acid supplementation on neurodevelopment in childhood: a review of human studies. Prostaglandins Leukot Essent Fatty Acids. 2010 Apr-Jun;82(4-6):305-14. doi: 10.1016/j.plefa.2010.02.007.