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Seafood and Health

Questions and Answers

In this section

Consumption Advice and Health Benefits of Seafood

Health Concerns of Seafood Consumption

The Fish Market in Canada




Consumption Advice and Health Benefits of Seafood Consumption



Q. What advice does Canada's Food Guide give about fish consumption?

DungenesscrabA. Canada's Food Guide encourages people to "eat at least two Food Guide Servings of fish each week." That's at least 150 grams each week. This statement was included because there is convincing evidence to support the association between the consumption of fish and a reduced risk of cardiovascular disease.

The Food Guide further advises people to "choose fish such as char, herring, mackerel, salmon, sardines and trout" as these fish contain very high amounts of the beneficial long-chain omega-3 fats.

The Food Guide also directs people to refer to Health Canada's latest advice for limiting exposure to mercury from certain types of fish.

Canada's Food Guide encourages a healthy eating pattern that includes a variety of foods from the four food groups. Following Canada's Food Guide will help Canadians obtain the vitamins, minerals and other nutrients they need for good health and will reduce the risk of obesity, type 2 diabetes, heart disease, certain types of cancer, and osteoporosis.

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Q. Should I stop eating fish because of the contaminants?

A. No. Health Canada and other expert groups around the world agree that seafood is an important part of a healthy diet. Fish and other seafood is an excellent source of high quality protein that is rich in vitamins and minerals, and most types are also low in saturated fat. Seafood also contains the long-chain omega-3 fats, which people should get from food because very little is produced by the body. These omega-3 fatty acids are considered important to heart health, and to the development of the brain, eyes and nerves. Eliminating an entire type of food or food group from the diet is generally unwise from a nutritional standpoint.

Most Canadians don't need to be concerned about mercury exposure as a result of fish consumption. In general, the types of fish that are most popular in Canada have levels of mercury far below the standards set by Health Canada. The risks of exposure to mercury from predatory fish (which eat a lot of other fish for food and thus have higher levels of mercury) are managed through Health Canada's standards and consumption advice. People who are at greater risk from the effects of mercury - pregnant and breastfeeding women, women who may become pregnant, and young children - can make informed choices about what types of fish they consume and how often, by following Canada's Food Guide and the consumption advice of Health Canada (and of regional authorities in the case of sport fish). That way, people can minimize their mercury exposure while they continue to gain the health benefits associated with eating fish.

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Q. What are the nutritional benefits of seafood?

A. Seafood is high in protein, vitamins and minerals, and most types are low in saturated fat. Fish is the most significant source of naturally occurring vitamin D in the Canadian diet. Seafood also contributes B-vitamins and valuable mineral nutrients to the diet such as selenium, iron, zinc, magnesium, potassium, copper and iodine.

halibut filetAlmost all types of seafood contain the long-chain omega-3 fats, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Evidence suggests that fish consumption and the associated intake of EPA and DHA from fish can contribute to heart health. DHA is known to support the normal development of the brain, eyes and nerves. There is evidence that regular consumption of seafood by pregnant and/or breastfeeding women can improve pregnancy outcomes, including duration of gestation and developmental outcomes (such as visual acuity and cognitive development) in the infants and young children of these mothers.

Some types of seafood have higher levels of the beneficial omega-3 fats than others. Types of seafood that contain higher levels of these fats and are also low in mercury include: anchovy, capelin, char, flatfish, Greenland turbot, hake, herring, lake whitefish, mackerel, monkfish, pollock, rainbow trout, salmon, sardines, smelt, mussels, oysters, crab and shrimp.

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Q. Nutritionally, how does seafood compare with meat?

A. As part of the Meat and Alternatives food group, seafood contributes protein, B-vitamins, and minerals such as selenium, iron, zinc, magnesium, potassium, copper and iodine. Compared to other meats in the Meat and Alternatives group, seafood is generally lower in saturated fat, higher in the omega-3 fatty acids EPA and DHA, and higher in the antioxidant selenium, all of which are important for health. Many North Americans consume greater than recommended amounts of saturated fat. Because many seafood choices are low in saturated fat, eating seafood more often in place of other animal foods can help people decrease their overall intake of total and saturated fats.



Q. What are the potential health benefits of consuming seafood?

perchA. The current evidence consistently suggests that eating seafood supports cardiovascular health in adults and normal growth and development in infants and young children.

  • Seafood consumption is associated with an overall benefit to the general population for decreased risk of cardiovascular deaths and cardiovascular events (such as myocardial infarction).
  • Consumption of seafood or fish-oil supplements during pregnancy and/or breastfeeding is associated with improved pregnancy outcomes, including increased duration of gestation as well as improved developmental outcomes (such as visual acuity and cognitive development) in the infants and young children of those mothers.

By themselves, the long-chain omega-3 fats EPA and DHA do not account for all of the health benefits associated with regularly eating seafood. For example, it is likely that these omega-3 fats, the other nutrients found in seafood, and eating seafood instead of choices that are higher in saturated fat, all contribute to the cardiovascular benefits.

Areas where the evidence is inconsistent or limited include the effects of seafood consumption on blood pressure, stroke, cancer, asthma, type 2 diabetes, Alzheimer's disease, depression, and behavioural disorders.

In many other areas, the research is still at the exploratory stage.

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lake whitefishQ. Are there benefits of fish consumption to an unborn baby?

A. Yes. Studies suggest that regular consumption of fish during pregnancy benefits the development of infants and young children, including visual acuity and cognitive development. The benefits are increased by limiting exposure to mercury. Therefore, pregnant women should consume types of seafood that are low in mercury in order to obtain the greatest benefit. Some examples of seafood that tend to contain very low levels of mercury include shellfish (for example oysters, clams, scallops, mussels), canned light tuna, salmon, crab, shrimp, trout, herring, haddock, Atlantic pollock (Boston bluefish), sole, flounder, lobster, Atlantic mackerel and lake whitefish.

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Q. Can eating seafood fight depression, Alzheimer's disease, ADHD, cancer, type 2 diabetes and other diseases and disorders?

salmonA. Although the evidence is evolving, it is currently not adequate to support benefits of seafood consumption in these areas. According to an expert review by the Institute of Medicine, evidence for a benefit associated with seafood consumption or fish-oil supplements on blood pressure, stroke, cancer, asthma, type 2 diabetes, or Alzheimer's disease is inconclusive. Whereas observational studies have suggested a protective role of the long-chain omega-3 fatty acids EPA/DHA for each of these diseases, supportive evidence from randomized clinical trials is either nonexistent or inconclusive. Similarly, at present there is no convincing evidence that Attention Deficit Hyperactivity Disorder (ADHD), other behavioural disorders, or asthma in children can be prevented or treated with seafood or EPA/DHA consumption.

For some other health benefits, though, the evidence is stronger. Seafood has been associated with developmental benefits (such as visual acuity and cognitive development) to infants or young children when their mothers consume seafood or fish-oil supplements during pregnancy and/or lactation. Also documented is an overall heart health benefit to the general population.

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Q. Should people be taking fish-oil supplements?

mackerelA. Eating fish rather than taking fish-oil supplements is the best public health approach to increasing intake of EPA and DHA. Whole fish provides a lean protein source and other nutrients whose benefits are not completely understood. For example, some evidence suggests that selenium may play a role in mitigating the negative effects of mercury exposure.

The American Dietetic Association and Dietitians of Canada (2007) indicate that:

  • "The risks and benefits of fish-oil supplementation during pregnancy and lactation, or in infants as a means to increase infant DHA [docosahexaenoic acid] are…unclear... Current evidence does not support a recommendation to increase EPA [eicosapentaenoic acid] and DHA to reduce risk of preterm delivery or pregnancy-associated complications." (page 1606)
  • "For vegans who do not consume any preformed sources of EPA and DHA, additional research is needed before recommendations can be made for these fatty acids, including supplements." (page 1602)

There is inconsistent evidence whether consumption of EPA/DHA-containing seafood or fish-oil supplements in individuals with a history of myocardial infarction will protect them from further cardiovascular events.

Here is the advice from the American Heart Association (2006) (page 89):

  • "On the basis of the available data, the AHA recommends that patients without documented CHD [coronary heart disease] eat a variety of fish, preferably oily fish, at least twice a week.
  • "Patients with documented CHD are advised to consume ~1 g of EPA+DHA per day, preferably from oily fish, although EPA+DHA supplements could be considered in consultation with their physician."

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Health Concerns of Seafood Consumption



Q. What is methylmercury?

A. Methylmercury is an organic form of mercury that can accumulate in the lean tissue of seafood (muscle), particularly in predatory fish species that eat a lot of other fish for food. Methylmercury is a neurotoxin that can adversely affect the brain and nervous system at high exposure levels. Children and the developing fetus are especially vulnerable to its effects.



Q. How does methylmercury get into our food?

A. Mercury finds its way into the aquatic food chain when naturally occurring mercury (such as from underwater volcanoes or rock surrounding bodies of water) or mercury from air pollutants leaches into or is deposited into oceans, lakes, rivers and streams. Once in the water, bacteria transform the mercury into methylmercury. Fish can absorb methylmercury from the water and ingest it when eating plankton or other smaller fish. Predatory species of fish, such as shark and swordfish, can accumulate mercury from eating a lot of other fish.



Q. What's Health Canada's advice for limiting how much mercury people get from seafood?

Prince RupertA. Most people don't need to worry about the level of mercury in seafood. The levels of mercury in most kinds of seafood, including the types eaten most commonly by Canadians, are very low (far below the standards set by Health Canada). However, for the predatory fish that are higher in mercury (fresh or frozen tuna, shark, swordfish, marlin, orange roughy or escolar), Health Canada has issued advice on the amounts to eat. For example, the general population can have up to 150 grams each week of these fish. Women who are pregnant or breastfeeding, or who may become pregnant, could eat up to 150 grams in a month of these fish, and advice is provided for children as well. As a precaution, Health Canada also issued advice for at-risk groups for limiting intakes of mercury from canned albacore (white) tuna, which some Canadians may eat in sufficient amounts to make it an appreciable source of mercury to the diet. (Note that Health Canada has not issued consumption advice for canned 'light' tuna because its mercury levels are lower.)

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Q. Why do advisories differ from country to country?

A. Fish consumption advice varies between countries because the fish consumption habits and the fish species that are consumed may differ between countries. Consumption advisories can also take into account other measures taken to protect consumers, such as the establishment of maximum levels for contaminants and enforcement activities. Health Canada's advice is based on the most up-to-date information related to the Canadian context. It is subject to regular revisions and updates in view of any new information gathered by Health Canada's scientists. However, the general consumption advice from various regulatory agencies remains consistent: people can enjoy the health benefits from eating fish by making informed choices.

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Q. Is farmed salmon safe to eat?

Atlantic SalmonA. Yes. Based on Health Canada's risk assessment, consuming farmed salmon does not pose a health risk to consumers. The levels of mercury in the muscle tissue of salmon are very low. Separate studies have identified other chemicals, such as polychlorinated biphenyls (PCBs), in the fat of both wild-caught and farmed salmon. These chemicals can be found in most fish - and in many other foods - but at levels much below what would be considered unsafe to human health.

Salmon continues to be a safe and healthy food choice as part of a balanced diet that includes a wide variety of healthy foods. Salmon is also an important source of nutrients, particularly omega-3 fats, which have been shown to contribute to a healthy diet.

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Q. Is farmed seafood as nutritious as fish harvested in the wild?

A. Yes, farmed seafood has just as much nutritional value as its wild counterparts. The nutrient content of seafood, wild or farmed, will vary according to the species, source and other factors. There also may be personal preferences in terms of texture or colour that may influence a person's impression of farmed and wild seafood such as salmon.

Farmed and wild seafood carry the same health benefits when they are part of a balanced diet. For example, all salmon is rich in omega-3 fatty acids, which are associated with a reduced risk of heart disease.



Q. Are there drug residues in farmed fish?

RestaurantA. Farmed fish are not fed or injected with growth hormones. Antibiotics, if they are required, are provided by veterinarians. Health Canada has clear rules about drug use on food animals. Maximum residue limits for each veterinary drug are set and must be met through appropriate withdrawal times following treatment before the fish can be harvested. The Canadian Food Inspection Agency monitors fish at federal processing plants as well as imported fish to ensure that only veterinary drugs that have been approved by Health Canada have been used and that the residue levels do not exceed the levels set by Health Canada.

When compared to land-based farmed animal production, salmon farming uses the least amount of antibiotics. In recent years, advances in vaccine development, similar to the practice used for raising livestock, have resulted in a significant reduction of antibiotic use.

The Canadian government is aware of the fact that unapproved or banned veterinary drugs may be used in some countries exporting seafood to Canada. Seafood from these countries is monitored thoroughly. In some instances, a whole country may be placed on the Import Alert List, meaning that 100% of shipments from that country are inspected for drug residues.

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Q. Is it safe to eat fish caught recreationally (sport fish)?

pickerelA. For most people, eating locally caught fish is perfectly safe. However, at-risk populations like pregnant women, infants and children should be especially careful. Anyone who plans to eat fish caught from local bodies of water should consult their provincial or territorial government for safety information. Links to provincial and territorial fish consumption advisories are available from the Environment Canada website.

Those who enjoy harvesting bivalve shellfish (clams, oysters, mussels) must avoid taking them from closed or unapproved harvesting areas. Fisheries and Oceans Canada and Environment Canada monitor bodies of water for the presence of naturally occurring toxins that can be present in bivalve shellfish, and warnings are posted for closed areas. These warnings must be respected.

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Q. Are the PCBs, dioxins and flame retardants in fish a health concern?

A. The levels of PCBs (polychlorinated biphenyls), dioxins and PBDEs (polybrominated diphenyl ethers, or flame retardants) in fish are not a health concern in retail fish. Health Canada has been monitoring the levels of various contaminants in many kinds of foods, including fish, for many years.lobster

  • The Canadian Food Inspection Agency and Health Canada completed a fish and seafood survey in 2002 that involved gathering a large number of samples and analyzing for various contaminants. Samples of farmed and wild caught char, oysters, salmon, shrimp and tilapia were analysed for dioxins, furans, PCBs, PBDEs, and veterinary drugs. The results indicate that the levels of these contaminants are well below Health Canada's current standards.
  • To date, there are no studies that link PBDE levels contained in food to any human health effects. Previous studies conducted on experimental animals, which had shown adverse effects related to PBDEs, involved exposure to levels that were over a million times higher than what is currently found in foods, including fish. Based on data currently available on exposure to PBDEs through food consumption in Canada, Health Canada has concluded that levels detected in fish sold in Canada are much below levels that would be considered unsafe to human health.
  • The average Canadian's exposure to dioxins and furans is well below the levels anticipated to cause adverse effects on human health.

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Q. Should people avoid eating shrimp because it contains cholesterol?

ShrimpA. Although generally low in total fat, some seafood, including shrimp, lobster and certain fish (such as salmon and sardines), contain moderate amounts of cholesterol (60 to 100 mg per half-cup or 75-gram serving).

Current nutrition recommendations, the Dietary Reference Intakes, recommend that "people maintain their dietary cholesterol intake as low as possible, while consuming a diet that is nutritionally adequate in all required nutrients."

These types of seafood are a source of important nutrients and are low in total fat and saturated fat, so they're a healthy choice occasionally as part of a balanced diet that includes a variety of foods. Using lower fat cooking methods like grilling, poaching or baking will help maintain their healthy fat profile.



Q. Is it safe to eat raw seafood?

kelpA. It is always best to cook seafood to minimize the risk of foodborne illness. Proper temperature control and safe food handling practices are very important in reducing the risk of foodborne illness. Some people are at greater risk for foodborne illness, and should never eat raw or partially cooked fish or shellfish (including refrigerated smoked fish products unless the products have been cooked, for example in a casserole). These groups include:

  • Pregnant women
  • Young children
  • Older adults
  • People whose immune systems are weakened
  • People who have decreased stomach acidity

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Q. Does cooking shellfish destroy toxins?

A. No, cooking shellfish does not destroy toxins, such as those that cause Paralytic Shellfish Poisoning, or chemical contaminants. That's why it is important to be sure that shellfish harvested recreationally are harvested from a safe area. The safest approach is to call the nearest Fisheries and Oceans Canada office to find out whether an area is 'open' or 'closed' for harvesting.



Q. How can I be sure to get safe, high quality seafood?
 
A. Follow basic food safety tips for buying, preparing, and storing fish and shellfish. Only purchase fish products from reputable retail and wholesale outlets. Ensure that these sources take adequate precautions to guarantee the quality and safety of seafood products. For example, check that fish is displayed either in a covered, refrigerated case where the temperature is controlled or on a thick bed of fresh ice that's not melting. Organizations at every governmental level (municipal, provincial and federal) cooperate in regulating the production, processing and sale of food products. If harvesting shellfish recreationally, be sure to harvest only from safe, 'open' areas - check with the nearest Fisheries and Oceans Canada office.

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The Fish Market in Canada



Q. What kinds of seafood are commonly harvested in Canada?

Northern PikeA. Canada has an abundance of freshwater fish and marine species - with more than 160 species in Canadian waters. Some of the more popular species available commercially are shown below:

  • Harvested from a marine environment - lobster, crab, shrimp, scallops, salmon (Chinook, sockeye, pink, coho, chum), clams, and groundfish (cod, halibut, haddock, hake, flounder, sole, etc.).
  • Harvested from freshwater - lake trout, lake whitefish, northern pike, pickerel and yellow perch.
  • Harvested through aquaculture - salmon (Atlantic, coho and Chinook), blue mussels, oysters and rainbow trout are the main species; others include Arctic char, tilapia, cod, sablefish, clams and scallops. In 2005, aquaculture accounted for about 12% of total Canadian fisheries production volume and 25% of production value.(1)

Reference:

1. Fisheries and Oceans Canada. Statistical Services, 2005 data.
www.dfo-mpo.gc.ca/communic/statistics/commercial/index_e.htm

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Q. Can fish have more than one common name?

A. Yes. The same fish species may be referred to by different names by different groups, organizations, jurisdictions, or countries. The Canadian Food Inspection Agency (CFIA) has developed a "Fish List" (http://active.inspection.gc.ca/scripts/fispoi/fplist/fplist.asp?lang=e) that lists the common and scientific names of a given fish species.



Q. What types of seafood contain very low levels of mercury?

Chinook SalmonA. In general, the types of fish that are most popular in Canada are also relatively low in mercury. Some examples of seafood that tend to contain very low levels of mercury include shellfish (for example oysters, clams, scallops, mussels), canned light tuna, salmon, crab, shrimp, trout, herring, haddock, Atlantic pollock (Boston bluefish), sole, flounder, lobster, Atlantic mackerel and lake whitefish.

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Q. How is Canada's government working to ensure seafood supplies are sustainable?

A. The federal department of Fisheries and Oceans Canada (DFO) is the federal government department that regulates and manages the Canadian fishery. DFO plays a leading role in managing and safeguarding oceans and inland waters and their resources for Canadians. DFO works to secure the future of Canada's wild fisheries through conservative management practices that focus on sustainable development and responsible fishing.

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Q. What is government's role in aquaculture?

Fish FarmA. Fisheries and Oceans Canada (DFO) is the lead federal department responsible for aquaculture management. DFO works with the provinces and other federal departments to create policy and regulatory conditions to ensure that the aquaculture industry develops in an environmentally responsible way while remaining economically competitive in national and international markets. All aquaculture operations are subject to rigorous environmental monitoring under a number of federal and provincial Acts to ensure they meet high standards of environmental sustainability. DFO conducts research to ensure the safety and sustainability of species that are permitted to be farmed. DFO's scientific research is peer-reviewed and reported openly on its website.

All processors in Canada, whether they deal with wild capture or farmed seafood, must have a Quality Management Plan (QMP) for their operations. Based on the principles of Hazard Analysis Critical Control Points (HACCP), the QMP ensures that all products are processed to ensure safety and wholesomeness.

Farmed fish are never given growth hormones, but they can be given vaccines and/or antibiotics if required. Health Canada has clear rules about drug use on food animals. Maximum residue limits for each veterinary drug are set and must be met through appropriate withdrawal times following treatment before the fish can be harvested. The Canadian Food Inspection Agency monitors fish at federal processing plants to ensure that only veterinary drugs that have been approved by Health Canada have been used and that the residue levels do not exceed the levels set by Health Canada.

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Q. Is imported seafood more of a health risk than domestic seafood?

A. All seafood for sale in Canada must meet the safety and quality standards set by Health Canada, regardless of country of origin (domestically produced or imported) and method of production (harvested from the wild or farmed). The Canadian Food Inspection Agency monitors imported fish products and conducts regular inspections, through the Fish Import Inspection Program, to prevent the marketing of unsafe, unwholesome or mislabelled products. The results are compared with the standards established by Health Canada. Imported seafood that does not meet the Canadian safety or quality standards cannot be distributed to consumers or further processed in Canada.

The CFIA uses a risk-based approach to determine the frequency at which to inspect imported products. The frequency varies based on food safety risk, the history of compliance of a particular product, the history of compliance of the processor, and the country of origin of the product.

The Canadian government is aware of the fact that unapproved or banned veterinary drugs may be used in some countries exporting seafood to Canada. Seafood from these countries is monitored thoroughly. In some instances, a whole country may be placed on the Import Alert List, meaning that 100% of shipments from that country are inspected for drug residues.

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Date Modified: 2008-06-01

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