Consumption of seafood during pregnancy is a controversial issue.
Prenatal care providers and parents are equally challenged by weighing the cons of toxic buildup in fish and shellfish (herein referred to as “fish” or “seafood”) with the pros of essential fatty acids needed for fetal development.
While fish contain a variety of nutrients that support fetal development, concern for toxic buildup of heavy metals in fish has led policy makers, prenatal care providers, and parents to evaluate the risk-benefit ratio more closely.1,2
RISKS OF CONSUMING SEAFOOD DURING PREGNANCY
There are a variety of potential persistent organic pollutants (POPs) such as methylmercury, dioxins, and polychlorinated biphenyls (PCBs) that may bioaccumulate in fish. Much public focus is on methylmercury exposure originating from fish.3,4
Large, predatory species have longer lives and consume other fish—for example, tuna, king mackerel, and swordfish—are repeatedly found to have the highest levels of methylmercury.5,6 Such predatory fish do not eliminate methylmercury well, causing it to be stored predominantly in their lean muscle tissue.7
Notably, contaminants in fish can cross the placenta and blood-brain barrier to reach the fetus. Since these contaminants are not well metabolized by the developing fetus, they tend to accrue in the fetus.6,8 This increases the risk for impaired neural development, low birth weight, altered newborn reflexes,8,9 and childhood behavioral disorders.10
BENEFITS OF CONSUMING SEAFOOD DURING PREGNANCY
On the other hand, fish are among the best sources of long-chain omega-3 fatty acids. And there is ample evidence demonstrating the benefit of omega-3 fatty acids for the developing fetus. In particular, omega-3 fatty acids are shown to support fetal neural development and normal birth weight, while minimizing the risk for miscarriage.1,11
Eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) are both necessary for healthy fetal growth and development. Moreover, sufficient DHA is particularly pertinent for optimal brain, cognitive, and visual function because it is a major constituent of cell membranes in the brain and retina.12,13
One study assessed brain maturity in relation to maternal blood levels of DHA by measuring sleep patterns in newborns. In contrast to mothers who had lower blood levels of DHA, mothers who had higher concentrations of DHA in their blood gave birth to newborns with more robust sleep patterns. This classification involved less active sleep and a smaller ratio of active sleep to quiet sleep in the initial 48-hour postpartum period.14 Thus, it is evident that the DHA plays an essential role in healthy brain development.
Furthermore, research indicates that the benefits of pregnant women consuming fish offset the risks of limiting such rich sources of omega-3 fatty acids.1,15 This is contingent on pregnant women consuming fish in accordance with safe dietary intake guidelines to maximize healthy neurodevelopment.
Current advice from the U.S. Environmental Protection Agency and Food and Drug Administration16 encourages pregnant and lactating women to consume 8-12 ounces of fish—focusing on a variety of low-mercury types as opposed to a single species or select few—per week. This translates to two to three 4-ounce servings each week.
RECOMMENDATIONS FOR CONSUMING SEAFOOD DURING PREGNANCY
Best Practices for safe intake of fish during pregnancy include:
- Choosing low-mercury fish such as sardine, haddock, and salmon.
- Avoiding fish such as Marlin, orange roughy, and swordfish with the highest level of mercury.
- Using the Environmental Working Group’s (EWG) Seafood Calculator to maximize your selection of fish highest in omega-3 fatty acids and lowest in mercury.
- Cooking all fish—including avoiding raw (e.g. sushi, ceviche), smoked, and lightly seared fish—until an internal temperature of at least 145° F is reached before consuming.8
- Monitoring fish contamination advisories for your locale.
SOURCING FISH & AVOIDING FISH FRAUD
Know how to source the best fish. This is an important topic when looking to minimize exposure to contaminants, while also being mindful of the richest sources of omega-3 fatty acids and environmental sustainability.
Unfortunately, most individuals are not provided with sufficient sourcing information about the fish they are consuming. Of great concern is the illegal mislabeling of fish, which involves fish species being substituted for other fish species. As the demand for fish increases and the worldwide trade of fish expands, an increased number in the market names of fish makes it more difficult to identify and label fish species.17
Such fraud has prompted eco-labeling18,19 such as the Marine Stewardship Council for wild fish and Aquaculture Stewardship Council for farmed fish. Even though eco-labels are intended to help consumers source high-quality and sustainable fish, there is often confusion about what the labels mean; thereby, providing evidence that public education about how to interpret eco-labeling is needed for consumers to make informed decisions.20
The international Oceana group—whose mission is to protect and restore the world’s oceans—has pioneered uncovering fish fraud. From 2010 to 2012, investigators used DNA testing (i.e. DNA barcoding) and found that sushi venues, restaurants, and grocery stores all participated in the mislabeling of fish. Substitutions involved fish species that were cheaper, more likely to have higher levels of contaminants (i.e. health advisory), and overfished species being marketed as healthier, wild, and sustainable species. For example, king mackerel was labeled as grouper, tilapia was sold as red snapper, and Atlantic halibut was labeled as Pacific halibut.21
More research is being conducted to implement DNA mini-barcoding to verify fish species in an effort to minimize fish mislabeling.17,22
Steps to minimize consumption of mislabeled fish23:
- Know what country the fish is from (use country-of-origin labeling).
- Look for eco-labels when purchasing fish and know what they mean.
- If purchasing farm-raised fish, know how it was grown to better assess its exposure to contaminants.
- If purchasing wild fish, know if it was caught using pole lines as opposed to long lines, which can catch contaminated marine species alongside the wanted fish.
- Make sure the price aligns with quality (e.g. is the price too good to be true?).
- Shop for in-season fish.
- Make sure labels match regulations (e.g. Wild Atlantic salmon is unavailable for retail because it is an endangered species).
- Know that certifiers of organic farmed fish may still employ chemicals to deter contaminations from parasites and use non-organic fish feed that contains contaminants.
- Use apps such as the The Seafood Watch App from the Monterey Bay Aquarium and the MCS Good Fish Guide App from the Marine Conservation Society.
- Build rapport with a local fishmonger and ask questions.
There is much to be learned about fish mislabeling and how to minimize the risk of fraudulent claims that could potentially be detrimental to your health and the health of pregnant women’s offspring.
SUPPLEMENTING WITH OMEGA-3 FATTY ACIDS
Some pregnant women who do not consume fish worry that they are not receiving enough EPA/DHA for the healthy growth and development—in particular, DHA for cognitive and neurodevelopment—of their fetuses. This is a valid concern. Although dietary recommendations for EPA/DHA vary throughout the world,24 most leading authorities advocate a minimum of 200 to 300 mg per day of DHA.25
In one study, researchers found that most of the participants did not consume the European Commission’s recommended minimum of 200 mg of DHA per day. A mere 27% of pregnant women and 25% of women three months postpartum had a daily intake of 200 mg of DHA per day,26 which equates to about two servings of fatty fish per week.27
When looking to supplement with EPA/DHA, it is important to understand the purpose of supplementation and research supporting desired outcomes. Nutrients tend to work synergistically when consumed as whole foods. And the nutrients other than omega-3 fatty acids (e.g. vitamin D, selenium, and protein) in whole fish may work to impart benefits different from those offered by supplementation with EPA/DHA alone.25,28
This is particularly relevant when considering the lack of robust evidence for or against the use of omega-3 supplementation during pregnancy for improved cognitive and visual outcomes of offspring.25,29 However, neurodevelopment is impacted by a number of factors (e.g. dietary patterns and home environment) as are cognitive tests (e.g. hunger and fear experienced by children while taking the tests, variations in development depending on age), which make assessing neurodevelopment challenging.1
Aside from the inconclusive reports about the benefit of supplementing DHA on cognitive function, researchers found that taking 900 mg of omega-3 fatty acids (800 mg EPA and 100 mg DHA) from 21 weeks’ gestation through delivery decreased the chance of offspring having an egg allergy during the first year of life30 when compared to the offspring of pregnant women not receiving the supplement. Another study in Denmark found that pregnant women who were administered an omega-3 supplement during their third trimester decreased the risk of offspring experiencing persistent wheeze and asthma.31 Moreover, a systematic review showed evidence of a small increase in the length of gestation with DHA supplementation during pregnancy, but supplementation did not decrease the rate for preterm delivery.32
In light of these findings and what is known about the role of dietary sources of DHA for supporting healthy pregnancy outcomes, supplementing with DHA is recommended for pregnant women who are unable to consume the recommended servings of low-mercury fish.25,27
Things to consider when looking for an EPA/DHA supplement27,33:
- Is it approved by the International Fish Oil Standards Program or does the label have the Global Organization for EPA and DHA Omega-3s (GOED) quality seal on it? These help ensure that the supplement does not contain harmful contaminants such as PCBs and methylmercury.
- Look to make sure the fish oil is in the concentrated triglyceride form—as opposed to the ethyl ester form—for maximum absorption.
- Prescription omega-3 supplements are available for some individuals such as those with hypertriglyceridemia. However, pharmaceutical omega-3 supplements are available in the ethyl ester form. To increase absorption, take them with a meal containing healthy fats.
- Avoid enteric-coated capsules, which may increase the risk of exposure to chemicals and may alter the amount of omega-3 fatty acids absorbed. If fish burps are an issue, storing them in the freezer may help reduce the chance of repeat occurring.
- Make sure the product does not smell rancid.
- A vegetarian algae-based source of DHA may increase EPA/DHA blood levels, but there is not enough research at the time of writing to conclude that this source offers comparable benefits to fish-based supplements of EPA/DHA.
- Talk with your healthcare practitioner to determine the right omega-3 supplement (e.g. EPA, DHA, or a blend of EPA/DHA) that is right for you. Consider having a blood test (e.g. omega-3 index) to monitor your blood levels of EPA/DHA for tailored dosing.
*If you are taking medication such as blood thinners, have a medical condition, or are preparing for surgery, talk to your doctor before taking an omega-3 supplement.
Consuming 8-12 ounces of a variety of cooked, low-mercury fish and being mindful of where the fish is sourced and local advisories for contamination issues will optimize the beneficial effects and minimize the risks of consuming fish during pregnancy.
With this information, parents can feel empowered to nurture their fetuses for healthy growth and neurodevelopment, which will help set their children up for maximal health throughout life.
Did you consume seafood during pregnancy? Share in the comments below!
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