Seafood Recommendations During Pregnancy - October 4, 2007

The contemporary challenge for maternal nutrition is to achieve optimal fetal growth and development, while minimizing complications and maintaining maternal health. This challenge continues after delivery, with the dietary need to ensure an optimal supply of vital nutrients in breast milk, while helping the mother regain her pre-pregnancy weight.

Fostering healthy fetal metabolism and in utero development, along with appropriate maternal weight gain, are fundamental goals in pregnancy. An optimal diet limits over-nutrition for the mother and under-nutrition for the fetus, thereby benefiting the overall health of the mother and her child in the following ways:

• Maintaining normal blood glucose concentrations and blood pressure levels throughout pregnancy, promoting a healthy metabolism and preventing pregnancy complications;
• Promoting development of the immune system and ability to combat infections;
• Optimal development of the fetal central nervous system, other organ systems and long-term health benefits of the child into adulthood;
• Optimal nutritional content of breast milk, thereby maximizing infant brain development;
• Prevention and/or more effective management of depression during and after pregnancy;
• Potential reduction of the risk of preterm labor and delivery;
• More rapid return to pre-conception weight after delivery.

General Guidance for an Optimal Diet During Pregnancy
An optimal pregnancy diet includes a balance of healthy meals and snacks, including frequent choices from among the following:

• Lean nutrient-dense protein sources, such as fish, eggs, beef, poultry, and dried legumes paired with brown rice.
• Complex carbohydrates that are sources of Vitamin A, C and B-complex (including folic acid), such as fruit, vegetables and whole grains (cereals and breads).
• Low-fat dairy products that are sources of protein, calcium, magnesium, phosphorus, and Vitamins B-12 and D, such as milk, yogurt and cheese.
• Long-chain omega-3 essential fatty acids, such as fish.

Conversely, pregnant women should limit high glycemic foods that can cause wide fluctuations in blood sugar and insulin levels. These include white bleached flour, quick-cooking rice, oatmeal or other instant grains, and refined carbohydrates such as sugar, soda, white bread, cookies, cakes and pies.

Fish Consumption During Pregnancy Is One of the Most Debated Dietary Controversies

There are many debates about optimal weight gain during pregnancy. While there is general agreement among medical professionals with the above dietary recommendations for optimal diet during pregnancy, fish consumption remains a heated topic of discussion. Fish is the dietary source with the highest levels of long-chain omega-3 essential fatty acids. However, there is concern about trace levels of methyl mercury that are present in fish.

Why Ocean Fish Consumption is Critical During Pregnancy

A critical concern regarding the typical American diet that has a great impact on maternal nutrition is the suboptimal intake of long-chain omega-3 essential fatty acids. Long-chain omega-3 fats cannot be synthesized in adequate amounts during periods of rapid fetal growth and development. Therefore, optimal levels must be maintained through consumption of dietary sources, such as fish, that are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). DHA is concentrated in nerve cell membranes and is essential for development of the fetal nervous system. The majority of DHA accumulates in the fetal brain during late prenatal and early postnatal development. Research studies have concluded that potential benefits from DHA in pregnancy for the developing fetus include improved visual, cognitive, motor and behavioral skills in the newborn that have been shown to last into childhood and may impact lifelong health and mental capacity.

Ocean fish is the richest dietary source of EPA and DHA; thus, it is a highly beneficial food during pregnancy and postpartum. Breast milk is the richest source of DHA for the infant and its adequacy is dependent on maternal levels of DHA. As in pregnancy, long-chain omega-3 fats are not synthesized in adequate amounts during the post-partum and breastfeeding period, so a diet rich in DHA is highly desirable. Furthermore, higher DHA intake has been linked to a reduction in preterm birth, as well as the prevention and management of postpartum depression.

Not All Polyunsaturated Fatty Acids Have the Same Benefits

Under dietary conditions with insufficient availability of DHA, a compensatory substitution of omega-6 fatty acid (FA), docosapentaenoic acid (DPA), occurs, resulting in an altered composition of cell membranes. Omega-6 essential fatty acids are the predominant fatty acid source in the typical American diet because oils, such as corn and soy, are rich dietary sources of omega-6 essential fatty acids and are found in most food and beverage sources. These oils, while promoting cardiovascular health, do not have the same beneficial impact on fetal nervous system development as do long-chain omega-3 fats.

Also, shorter-chain omega-3 fats from flax and walnuts do not efficiently convert to active DHA and should not be seen as a substitute for long-chain omega-3 essential fats from ocean fish. Small amounts of plant omega-3 fatty acids are converted to EPA, and very little is converted to DHA. To derive optimal benefit, it is important to ensure that the omega-3 fatty acids consumed during pregnancy are the long-chain fatty acids from seafood and not the shorter-chain fatty acids from plant sources.

Considerations Related to Methyl Mercury in Seafood

While long-chain omega-3 essential fats are required during pregnancy for optimal outcomes, it is important to understand the risk-benefit equation for women regarding consumption of seafood during this important time.

The detection of trace amounts of methyl mercury in fish has raised concern about the development of possible impairments in cognitive function. However, recent studies indicate that the nutritional benefits of fish consumption during pregnancy greatly outweigh potential risks from trace methyl mercury consumption. Oily ocean fish are high in long-chain omega-3 fats and an important source of the mineral selenium, which is essential for thyroid function and anti-oxidation. There is a growing body of evidence that selenium in ocean fish may also counteract potential negative influence of mercury exposure. While a nutritional deficiency from insufficient seafood consumption (long-chain omega-3 fatty acids) is quite common, the risk of mercury toxicity is exceedingly rare.

Seafood Corrects a Nutritional Deficiency During Pregnancy

Consumption of oily ocean fish, which are the richest fish sources of DHA and EPA, corrects a common nutritional deficiency that exists in pregnancy (based on ALSPAC and other supporting literature). Ocean fish, including salmon, tuna, sardines and mackerel, are natural sources that meet the need for DHA and EPA in pregnancy and provide a lean protein source with important micronutrients like vitamins B, D, zinc, iodine and selenium.

Recommendations for Pregnant Women Regarding Fish Consumption

I. Pregnant, breastfeeding and postpartum women are recommended to consume a minimum of 12 ounces of seafood per week (salmon, tuna, sardines), or DHA-fortified eggs. Six ounces of the recommended fish per week can come from albacore tuna.

This recommendation for women who are pregnant, postpartum or nursing is consistent with the following recommendations:

1) United Kingdom Scientific Council on Nutrition (SCAN) recommends 2-3 portions of oily fish per week. SCAN notes that the mercury content of tuna is lower than that of shark, swordfish or marlin, but higher than that of other commonly consumed fish, and considers that consumption of two 140g portions of fresh tuna, or four 140g portions of canned tuna, per week before or during pregnancy would not be expected to result in adverse effects on the developing fetus. [Scientific Advisory Committee on Nutrition. Advice on fish consumption: benefits and risks. 2004. Accessible at: www.sacn.gov.uk/reports]

2) The Health Council of the Netherlands advises consumption of two portions of fish per week, at least one of which should be oily fish. [Health Council of the Netherlands. Guidelines for a Healthy Diet. 2006. Accessible at: www.gr.nl/samenvatting.php?ID=1481]

3) The Nordic Council of Ministers (Long chain omega-3, 0.5 en%) [Nordic Council of Ministers. Nordic Nutrition Recommendations. 2004. Copenhagen, Denmark. Excerpt accessible at: http://www.norden.org/pub/sk/showpub.asp?pubnr=2004:01]

4) Superior Health Council of Belgium (long chain n-3, 250 mg/d) [Belgian Federal Public Service. Superior Health Council. Advisory Report. Recommendations and claims made on omega-3 fatty acids. 2004. Accessible at: https://portal.health.fgov.be/pls/portal/docs/PAGE/INTERNET_PG/HOMEPAGE_MENU/
ABOUTUS1_MENU/INSTITUTIONSAPPARENTEES1_MENU/HOGEGEZONDHEIDSRAAD1_MENU/
ADVIEZENENAANBEVELINGEN1_MENU/ADVIEZENENAANBEVELINGEN1_DOCS/
OMEGA-3%20ENGLISH.PDF]

5) National Health and Medical Research Council of Australia (Long chain omega-3, 110-145mg/d) [Ministry of Health, Australian Government. Nutrient Reference Values for Australia and New Zealand. Executive Summary. 2005. Accessible at: http://www.nrv.gov.au/Default.aspx.]

6) Institute of Medicine USA, (long chain omega-3, 140 mg/d) [Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2002. National Academy Press, Washington, DC. Accessible at: http://www.iom.edu/?id=12702]

II. Consumption of ocean fish rather than ingestion of fish oil supplements is the best public health approach. Whole fish itself rather than fish oil supplements has been linked to reductions in preterm labor, providing a lean protein and likely other beneficial nutrients that are not completely understood.

If a pregnant woman cannot consume whole fish, a number of public health bodies endorse fish oil supplements instead. The European Commission sponsored a 2007 consensus statement, which recommends a minimum of 200 mg/day of DHA supplements for pregnant and lactating women (Koletzko, 2007), while an earlier workshop sponsored by the National Institutes of Health and the International Society for the Study of Fatty Acids and Lipids (ISSFAL) recommended 300 mg/day of DHA (Simopoulos, 1999). More recently, ISSFAL has recommended 500 mg/day DHA and EPA for all adults to maintain a healthy cardiovascular system, further emphasizing the importance of these vital nutrients.

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