EWG’s Consumer Guide to Seafood
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Why Eat Seafood? And How Much?
EWG’s Consumer Guide to Seafood: Why Eat Seafood? And How Much?
In June of this year the federal Food and Drug Administration and Environmental Protection Agency proposed new guidelines that encourage pregnant and nursing women to consume eight to 12 ounces of seafood of a variety of seafood per week, choosing from varieties lower in mercury (FDA 2014a).
The FDA/EPA proposal represented a significant change from the agencies’ 2004 guidelines, which advised pregnant women, those who might become pregnant and nursing mothers to eat no more than 12 ounces of low-mercury seafood.
This time around, the agencies set a floor as well as a ceiling on seafood consumption. They recommend that pregnant women, those who might become pregnant and nursing mothers boost their intake of fish dramatically, from 3.6 ounces per week, the current national average, to eight to 12 ounces weekly (FDA 2014a). They said young children should eat more fish, the amount dependent on their weight and age. This advice echoed the Obama administration’s Dietary Guidelines for Americans, published in January 2011, which said all adults should eat eight to 12 ounces of “a variety of seafood types” (USDA 2010).
The basis for this recommendation is research indicating that “good fats,” particularly polyunsaturated omega-3 fatty acids, offer extraordinary and unique health benefits.
The two most beneficial omega-3 fatty acids -- docosahexaenoic acid, known as DHA, and eicosapentaenoic acid, known as EPA -- have been shown to reduce inflammation and severity of heart and retinal diseases. Children born to mothers who ate low-mercury seafood during pregnancy experienced better functioning brain and nervous systems. They scored two to six points higher on intelligence tests than children whose mothers ate little fish during pregnancy (Oken 2005). A diet rich in omega-3s lowered blood triglycerols, reduced arrhythmias and decreased the risk of sudden death from heart disease (USDA 2010).
Fish and shellfish are low in fat, high in protein and good sources of iodine, vitamin D and selenium, often deficient in the Western diet. But decades of industrial activity, particularly emissions from coal-fired power plants, have released mercury and other pollutants into oceans and waterways. Those contaminants end up in seafood. While most commercial fish and shellfish contain some mercury, concentrations vary depending on the fishes’ ages, diet, region of harvest and other factors. Large predatory fish, including tuna, shark, marlin and swordfish, which eat smaller fish, accumulate considerable mercury over life spans that may run decades.
Omega-3 concentrations vary widely among species but are typically highest in species that dwell in cold water and have oily flesh. Some fish species are high in mercury but low in omega-3s. Others have higher concentrations of omega-3s with very little mercury.
EWG strongly agrees with the administration’s Dietary Guidelines for Americans when it calls for Americans to eat more fruits and vegetables, high-fiber whole grains and seafood, and to eat less sugar, solid fat, refined grains and sodium. However we disagree with the blanket recommendation that all adults aim to eat 8 to 12 ounces of seafood per week. Many people are at low risk for heart disease, including vegetarians and other adults with an otherwise healthy diet. If all Americans followed the federal government’s advice, the amount of seafood consumed in the U.S. could triple, and global fisheries could suffer.
High-risk populations – pregnant women, children and people with heart disease—are likely to benefit from eating more seafood, provided they select varieties with the least mercury and optimum omega-3 content. To do so they need specific and detailed information about omega-3s and mercury content of common varieties.
EWG’s investigation of government and scientific data on seafood contamination and omega-3 content has found that seafood varied widely on both counts. We conclude that the federal government’s approach, advising Americans to “eat more fish and to eat a variety of fish from choices that are lower in mercury,” is inadequate. The reasons: shoppers may not know that some commercial species likely to contain less mercury are also very low in omega-3 fatty acids.
In an analysis released earlier this year, EWG cautioned that not everyone who follows the government’s dietary guidelines and eats two or three meals per week would achieve the intended health benefits. This is a particular concern for pregnant women and young children who eat fish higher in mercury (EWG 2014). Our analysis found that:
- 10 of 35 common commercial species have too much mercury for women of average weight to eat twice weekly during pregnancy.
- 19 of the 35 have too much mercury for children.
The proposed FDA/EPA advisory urges pregnant women and children to avoid four species -- swordfish, tilefish, king mackerel and shark. EWG goes further, recommending that people also limit their consumption of a larger number of moderate-mercury species.
Not all fish are equally nutritious. Twenty-one of the 35 common fish and shellfish we investigated would not provide an adequate amount of omega-3s when eaten twice weekly. This includes most fish and shellfish species often found in the American diet.
Dangerous substances besides mercury can build up in fish and shellfish. Among them are dioxin and other persistent pollutants. While these pollutants are generally less harmful than mercury, their presence is a reminder that people who eat lots of fish or shellfish should pay attention to local seafood advisories and select only low-mercury species.
EWG recommends that people restrict their seafood consumption to two or three meals per week. Beyond that amount, the beneficial effects of omega-3s subside and the risks posed by contaminants add up.
How do you know you’re eating enough seafood and the right seafood?
It all depends on who you are, your age, your pregnancy status and your health.
If you are considering getting pregnant, are pregnant or nursing
Federal nutrition guidelines recommend that you consume an average of 250 milligrams daily of DHA and EPA, the two omega-3 fatty acids found primarily in seafood (USDA 2010). The most critical period is the last 10 weeks of pregnancy.
Not all seafood species are equal. One to two servings of a high-omega-3 species like salmon, sardines or Pacific or Atlantic mackerel can meet the weekly recommendation for omega-3s. But a pregnant woman would need to eat five or more servings of tilapia, shrimp or catfish to get the optimum amount of omega-3s.
Because mercury from seafood can linger in your body, you should limit your mercury consumption before you conceive, or soon in pregnancy. Mercury can pass through breast milk. It is wise to continue avoiding higher-mercury fish while breastfeeding.
If you are feeding children
Children benefit from eating seafood but should consume smaller portions. Always serve low-mercury seafood. Children should eat no more than one serving of canned light tuna per week. Children should never eat canned albacore tuna, also known as white tuna.
If you have been diagnosed with heart disease
The Obama administration’s Dietary Guidelines for Americans report “moderate evidence” that consumption of two servings of seafood weekly can reduce the number of deaths from heart attacks and strokes. But eating more than two meals a week does not appear to offer additional benefits (USDA 2010).
On the other hand, eating high-mercury fish can erode some cardiac benefits of seafood (Burger 2013 citing Gullar 2002, Stern and Korn 2011). For this reason, people with heart disease should make an effort to limit their exposure to mercury.
If you are at low risk for heart disease and not pregnant
For most adults, seafood is beneficial but not essential.
Adults who eat fish frequently, particularly those who eat sushi, recreationally-caught fish or high-mercury fish, are at risk for mercury toxicity. Some studies of people who ate large quantities of fish or species high in mercury have reported neurological and other health problems.
If you eat fish or shellfish caught from local waterways
Many streams and rivers are contaminated with mercury and other pollutants from industrial pollution. Locally-caught fish can sometimes be more polluted than those purchased in stores. State and local governments have issued dozens of location-specific warnings and guidelines for taking fish and shellfish from polluted lakes and streams. Check the U.S. Environmental Protection Agency’s searchable webpage for fish advisories by state, or check your state’s website for information about local waterways. When a local waterway is not the subject of a specific advisory, the FDA/EPA advisory recommends that adults eat no more than six ounces and children, one to three ounces, of any non-commercial fish and seafood per week (FDA 2014a).
If you love sushi and eat it frequently
People who eat sushi weekly, particularly high-mercury types such as tuna, are at risk for excessive mercury, according to a survey of more than 1,000 New Yorkers and New Jerseyans by scientists at Rutgers University (Burger 2013). Tuna in sushi had three to 10 times more mercury than eel, crab, salmon and kelp rolls. Tuna served at upscale sushi restaurants and prepared as sashimi and nigiri had the highest mercury concentrations of all. Tuna in maki rolls sold at supermarkets and less expensive restaurants had lower mercury levels. The Rutgers study calculated that the 10 percent of respondents who ate the most sushi would ingest roughly triple the recommended daily intake for mercury (Burger 2013).
Many common sushi varieties are made from overharvested fish species. Check Monterey Bay Aquarium’s Sushi Guide for sustainability ratings.
If you eat canned tuna
Americans eat more than 400 million pounds of canned imported tuna because it is affordable and can be stored for a long time. Albacore tuna, also called “white” tuna, contains significant amounts of omega-3s but also significant mercury contamination (USDA 2013, Karimi 2012, Consumer Reports 2011, Mercury Policy Project 2012). “Light” tuna is usually skipjack tuna but can also be yellowfin or tongol tuna. These varieties have lower mercury levels than albacore but fewer omega-3s (USDA 2013).
The June FDA/EPA advisory recommended that pregnant women limit their consumption of albacore tuna to six ounces weekly (FDA 2014a). EWG is more cautious: we recommend that children, pregnant women and nursing mothers eat no more than two servings of albacore tuna per month, with the exact quantity depending on age and weight. [See EWG’s Seafood Calculator]
The June FDA/EPA advisory said canned light tuna was relatively lower in mercury (FDA 2014a). We disagree. EWG recommends no more than one serving per week of light tuna for children and two servings for pregnant or nursing women.
If you don’t eat seafood
Omega-3s are important during pregnant and early childhood. But these fats are not as necessary for other adults, provided they eat an otherwise healthy diet. Pregnant women who don’t eat fish can find omega-3 fatty acids in fish oils, fortified foods and omega-3 supplements.
Oils containing the important omega-3 fatty acids DHA and EPA can be made from a variety of seafood species or extracted from algae. In general, dietary supplements are poorly regulated, so consumers cannot determine the supplements’ true omega-3 content. Nor can they be sure mercury or other contaminants are not present. Few data are available on this problem. Concentrations of mercury and other contaminants in supplements appear to be low and vary depending on the species of fish that serve as the basis for the particular supplement (Consumer Lab 2013, Covaci 2010, Foran 2003, Levine 2005). Consumer Labs tests of fish oils sold in the U.S. found none with more than 0.01 parts per million mercury; in other words, a dose of a supplement contained less mercury than a single serving of most fish (Consumer Labs 2013).
Some milk, eggs and margarines are fortified with DHA. Others foods, including canola oil, soybean oil, flax seeds, chia seeds and walnuts contain a third type of omega-3 fat known as alpha-lineoic acid or ALA, which the body can convert to DHA and EPA. However, people generally convert less than 10 percent of the ALA in their diet to EPA, which is then converted to DHA. This makes ALA consumption a less effective source of good fats, and less reliable option during pregnancy.
If you buy foods that claim to be fortified with omega-3s, check the product labels for DHA and ALA. (No foods are supplemented with EPA.) Nutritional guidelines suggest that women consume 250 milligrams of DHA and EPA daily during pregnancy. Many foods contain far less.
The U.S. government’s Medline database rates fish oil supplements as “effective” for people with high triglycerides and “likely effective” for people with heart disease. But fish oil supplements are rated only as “possibly effective” treatments for many other health conditions, including arthritis, stroke, osteoporosis, age-related eye disease and attention deficit-hyperactivity disorder (MedlinePlus 2014).
There is no reliable scientific evidence that pregnant women and nursing mothers who take omega-3 supplements have infants who enjoy benefits in growth, neurodevelopment and vision comparable to women who ate seafood during pregnancy (Campoy 2012).
Fish oil supplements appear to be slightly less beneficial for cardiac patients than a seafood-rich diet (Rizos 2012), perhaps because seafood has important trace nutrients like iodine, vitamin D, vitamin B12 and selenium. As well, people who eat seafood are probably less inclined to eat unhealthy proteins like fatty or highly processed meats.
EWG recommends that women who are pregnant and anyone at risk for cardiac disease consult their physicians if they do not eat seafood frequently to discuss other ways to add omega-3s to their diets.