Consistent Evidence for Benefits
Seafood is a nutritious food containing nutrients that play a well-established role in:
- normal growth and development
- energy metabolism
- building and repairing body tissues
- formation and maintenance of bones and teeth
- formation of red blood cells
- building antibodies
At this point the evidence suggests that eating seafood supports heart health in adults and normal growth and development in infants and young children.
There’s a sufficient amount of consistent evidence for associations between:
- Increased seafood consumption and a decreased risk of cardiovascular deaths and cardiovascular events (such as myocardial infarction) in the general population.
- Maternal seafood or fish-oil supplement consumption during pregnancy and/or breastfeeding and improved pregnancy outcomes, including:
- increased length of gestation, and
- improved developmental outcomes (such as visual acuity and cognitive development) in infants and young
http://www.ats-sea.agr.gc.ca/sea-mer/hs-ba-eng.htm (Sept 09)
Should I stop eating fish because of the contaminants?
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.
What about mercury levels in fish?
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.
What are the nutritional benefits of seafood?
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.
Almost 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.
Nutritionally, how does seafood compare with meat?
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.
What are the potential health benefits of consuming seafood?
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.
Are there benefits of fish consumption to an unborn baby?
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.
Should people be taking fish-oil supplements?
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.
Is farmed salmon safe to eat?
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.
Is farmed seafood as nutritious as fish harvested in the wild?
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.
Are there drug residues in farmed fish?
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.
Are the PCBs, dioxins and flame retardants in fish a health concern?
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.
- 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.
Should people avoid eating shrimp because it contains cholesterol?
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.
http://www.ats-sea.agr.gc.ca/sea-mer/hs-qu-eng.htm#4 (Sept 09)