Seafood and Health

Why Eat Seafood?

Seafood is an important part of a healthy diet.

Canada's Food Guide recommends that Canadians eat at least two Food Guide Servings of fish each week. That amounts to at least 150 grams of cooked fish every week (or about 5 ounces or 1 cup). The Food Guide also advises Canadians to choose fish such as char, herring, mackerel, salmon, sardines and trout, which contain especially high amounts of beneficial long-chain omega-3 fats.

• Many Canadians are not meeting this goal. They could be missing out on the health benefits from eating seafood.
• Seafood is very nutritious. Seafood, which includes fish, shellfish and crustaceans, contains high quality protein along with other essential nutrients. Seafood is unique among protein foods because it is generally higher in the long-chain omega-3 fats, lower in saturated fats, and higher in the mineral selenium than most other choices. Seafood also provides B-vitamins, vitamin D, and the minerals iron, zinc, magnesium, potassium, copper, and iodine.
• Seafood has important health benefits. A well-balanced diet that includes a variety of seafood contributes to heart health in adults and to normal growth and development in infants and young children. For example, the long-chain omega-3 fat DHA is known to support the normal development of the brain, eyes and nerves. 
  
  Eating seafood can have other health benefits besides those from the long-chain omega-3 fats and other nutrients. For example, when seafood is eaten in place of choices that are higher in saturated fat, this indirectly contributes to the benefits to heart health. 
  
  Although the evidence remains inconclusive, scientists are also investigating whether seafood and its omega-3 fats can benefit other conditions, including asthma, cancer, depression, Alzheimer's disease and behavioural disorders. Research into many more areas is just at the exploratory stage.

To learn more:

• What Are the Health Benefits of Eating Seafood?
• Evidence behind the Canada's Food Guide recommendation for fish

The Nutritional Value of Seafood

Seafood contributes a range of nutrients to the Canadian food supply and has important health benefits. Seafood is an excellent source of high quality protein, is rich in vitamins and minerals, and provides healthy omega-3 fats. These nutrients have many metabolic functions and play important roles in achieving and maintaining good health. Most types of seafood also are low in saturated fat.

Protein, Vitamins and Minerals

• Seafood is part of the Meat and Alternatives food group, and contributes protein, B-vitamins, and minerals such as selenium, iron, zinc, magnesium, potassium, copper and iodine. For example, almost all types of seafood are an excellent source of vitamin B12, and seafood generally has higher levels of the antioxidant selenium than other choices in the Meat and Alternatives group.
• Fish is the most significant source of naturally occurring vitamin D in the Canadian diet.
• Many types of seafood also provide calcium: canned salmon and sardines eaten with the bones are a good source of calcium while other types, including clams, crabs, oysters, lobster, halibut, and herring, are a source of this nutrient.

Healthy Fats

• Seafood is our primary dietary source of the long-chain omega-3 fatty acids called EPA (eicosapentaenoic acid, 20:5n-3) and DHA (docosahexaenoic acid, 22:6n-3).
  - People should get EPA and DHA through food because very little is produced by our bodies. We can only synthesize these long-chain polyunsaturated fatty acids in limited amounts from alpha-linolenic acid, the precursor omega-3 fatty acid, which is found in some vegetable oils (notably canola and soybean oils), walnuts, and ground flaxseeds.
  - EPA and DHA are considered important to heart health, and to the development of the brain, eyes and nerves.
  - Oily fish, such as mackerel, herring and salmon, are an excellent way to obtain these omega-3 fatty acids.

Omega-3 fatty acid content (EPA and DHA) of selected seafood

Type of fish	EPA + DHA (mg/100 g)
Blue mussels	780
Char	750-900
Herring	1800-2000
Mackerel	400-1850
Oysters	440-1370
Salmon	450-2150
Sardines	980-1400
Trout	700-1100
Tuna	270-1500
Values are based on data from the Canadian Nutrient File, 2007b. Actual nutrient content will vary somewhat according to the species, source and other factors.

• Many seafood selections, depending on how they are prepared, are lower in total fat and saturated fat than other animal protein foods.
  - By substituting seafood more often for other animal foods, people can decrease their overall intake of total and saturated fats.
  - To keep the fat profile as healthy as possible, seafood should be prepared using lower fat cooking methods, like grilling, poaching, broiling or baking, rather than battered and fried.

To learn more:

• A primer on fats
• Nutritional value of selected types of seafood and other animal food choices (comparison chart)
• The Fish Market in Canada
  (includes nutrition information on about 40 types of seafood commonly available in Canada, and links to factsheets that provide more information about some of the species)

A Primer on Fats

Oils and fats supply calories and essential fats and help our bodies absorb the fat-soluble vitamins A, D, E and K. The type of fat consumed is as important for health as the total amount consumed.

Fats are composed of three fatty acid molecules bound to a glycerol backbone. The fatty acids can be saturated, trans or unsaturated (monounsaturated or polyunsaturated). This classification is based on whether the fatty acid chain contains no double bonds (saturated fatty acids; SFA), one double bond (monounsaturated fatty acids; MUFA), or more than one double bond (polyunsaturated fatty acids; PUFA). PUFA are further classified as n-3 (omega-3) or n-6 (omega-6) fatty acids, based on the position of the first double bond from the methyl end of the fatty acid chain. A fatty acid is called "trans" if the double bonds are configured a certain way. Trans fatty acids are chemically classified as unsaturated fatty acids but behave more like saturated fatty acids in the body.

Saturated and trans fats

A diet low in saturated fat and trans fat can help reduce the risk of cardiovascular disease. These fats are not essential in the diet. The current nutrition recommendations, the Dietary Reference Intakes, recommend that people try to achieve a diet low in saturated fat and maintain their trans fat intake as low as possible while consuming a nutritionally adequate diet.

• SFA are found in animal fats and tropical vegetable oils. Meat and dairy products contribute approximately 60% of SFA in the North American diet.
• Trans fats are found mostly in hard stick margarines and foods made with partially hydrogenated oil or vegetable shortening such as pastries, doughnuts, cookies, crackers and deep-fried food.
• Currently, the food industry is in the process of replacing partially hydrogenated oils with healthier oils (such as high oleic oils) in the preparation of fast foods and processed foods. However, preparation of some deep-fried foods, pastries and bakery foods (such as doughnuts, cookies and crackers) require hard fats such as tropical oils, margarine, or shortening that are high in SFA. Thus, these foods may contain high amounts of SFA.

Unsaturated fats

People should consume mostly sources of unsaturated fats such as vegetable oils, soft non-hydrogenated margarines, nuts, seeds and fatty fish. These foods are important sources of "essential" fats (omega-3 and omega-6 PUFA) that cannot be produced by the body and must be obtained from the diet.

• MUFA are present in vegetable, nut, and seed oils, as well as in meats and dairy products. The major dietary MUFA is oleic acid, found in olive oil, canola oil, mid-oleic sunflower oil, and other mid- and high-oleic vegetable oils, as well as in peanuts, pistachios, almonds, and avocados.
• PUFA are found in vegetable, nut, and seed oils, as well as in seafood, with the amounts of omega-3 and omega-6 fatty acids varying greatly.
  • Omega-6 fats are found in some nuts and seeds, safflower, sunflower, corn and soybean oils, and soft margarines with no trans fat.
  • There are three main types of omega-3 fats found in foods:
    - Alpha-linolenic acid (ALA)
    ALA, the predominant dietary omega-3 fatty acid, is an "essential" fat in the diet because our bodies cannot produce ALA. Flaxseed, canola oil and soybean oil contain high amounts of ALA. Other sources are walnuts, omega-3 enhanced eggs, soybeans, sunflower seeds, some soft margarines and most vegetable oils.
    - Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA)
    The long-chain omega-3 fats EPA and DHA play a role in heart health. DHA also supports the development of the brain, eyes and nerves. Although the body can convert ALA to the long-chain omega-3 fatty acids, the conversion to EPA and especially to DHA is limited in humans; thus, people should get EPA and DHA through food. Fish and other seafood is the primary food source of EPA and DHA.

Omega-3 and Omega-6 Polyunsaturated Fatty Acids

Type	Name	Abbreviation	Structure	Main Food Sources
Omega-3	alpha-linolenic acid*	ALA	18:3n-3	Walnuts, ground flaxseeds, canola oil, soybean oil
	eicosapentaenoic acid	EPA	20:5n-3	Fatty fish, fish oils
	docosapentaenoic acid	DPA	22:5n-3	Fatty fish, fish oils
	docosahexaenoic acid	DHA	22:6n-3	Fatty fish, fish oils
Omega-6	linoleic acid*	LA	18:2n-6	Corn oil, safflower oil, soybean oil, cottonseed oil, sunflower oil
	gamma-linolenic acid	GLA	18:3n-6	Evening primrose oil, borage oil, black currant seed oil
	arachidonic acid	AA	20:4n-6	Meat, poultry, eggs

*essential fatty acids that the human body needs but cannot synthesize

To learn more:

• Position of the American Dietetic Association and Dietitians of Canada: Dietary Fatty Acids. J Am Diet Assoc 2007;107:1599-1611 www.dietitians.ca/news...
• Otten JJ, Hellwig JP, Meyers LD (eds): Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Institute of Medicine, Food and Nutrition Board. Washington, DC: National Academies Press, 2006 www.nap.edu/catalog.php?record_id=11537

*PDF Format, requires Adobe Acrobat Reader

Nutritional Value of Selected Types of Seafood and Other Animal Foods (*PDF)

Food	Nutrient content (per 100 grams cooked)
	Energy (kcal)	Protein (g)	Total fat (g)	Saturated fat (g)	Omega-3 fats
					DHA (g)	EPA (g)	ALA (g)
SEAFOOD
Flatfish (flounder, sole, plaice) (baked or broiled)	117	24.16	1.53	0.363	0.258	0.243	0.016a
Halibut, Atlantic and Pacific (baked or broiled)	140	26.69	2.94	0.417	0.374	0.091	0.083a
Lobster, Atlantic (boiled or steamed)	98	20.50	0.59	0.107	0.031	0.053	0.000a
Mackerel, Atlantic (baked or broiled)	262	23.85	17.81	4.176	0.699	0.504	0.113a
Oysters, Pacific (boiled or steamed)	163	18.90	4.60	1.020	0.500	0.876	0.064a
Rainbow trout, farmed (baked or broiled)	169	24.27	7.20	2.105	0.820	0.334	0.082a
Salmon, Atlantic, farmed (baked or broiled)	206	22.10	12.35	2.504	1.457	0.690	0.113a
Salmon, Pacific sockeye, wild (baked or broiled)	216	27.31	10.97	1.917	0.700	0.530	0.062a
Shrimp, mixed species (boiled or steamed)	99	20.91	1.08	0.289	0.144	0.171	0.012a
Snow crab (boiled or steamed)	115	23.72	1.51	0.183	0.145	0.332	0.003a
Tuna, canned, light (in water, drained, unsalted)	116	25.51	0.82	0.230	0.223	0.047	0.000a
Tuna, canned, white (in water, drained, unsalted)	128	23.62	2.97	0.792	0.629	0.233	0.071a
BEEF
Ground beef (lean, broiled, well done)	252	28.03	14.65	5.827	0.000	0.000	0.052a
Roast beef (boneless eye of round roast, 3mm trim, roasted)	197	31.90	6.33	2.770	-	-	0.020
Top sirloin (steak, 3 mm trim, broiled)	195	28.10	8.22	3.430	-	-	0.030
PORK
Cured ham (boneless, regular, roasted)	178	22.62	9.02	3.120	0.000	0.000	0.240a
Pork loin (boneless rib roast, roasted)	244	28.22	13.79	5.310	0.000	0.000	0.090
Ground fresh pork (medium, pan-fried)	299	24.50	21.50	8.020	0.000	0.030	0.240
POULTRY
Chicken breast, meat and skin (roasted)	188	25.84	8.74	2.332	0.019	0.006	0.075a
Chicken breast, meat only (roasted)	147	29.93	2.08	0.552	0.015	-	0.015a
Turkey, meat only (roasted)	170	29.32	4.97	1.640	0.040	0.000	0.040a
Turkey, ground (cooked)	235	27.36	13.15	3.390	0.030	0.000	0.150a

Nutritional Value of Selected Types of Seafood and Other Animal Foods - continued

Food
	Cholesterol (mg)	Calcium (mg)	Iron (mg)	Magnesium (mg)	Selenium (µg)	Zinc (mg)	Vitamin B6 (mg)	Vitamin D (µg)
SEAFOOD
Flatfish (flounder, sole, plaice) (baked or broiled)	68	18	0.34	58	58.2	0.63	0.240	1.500
Halibut, Atlantic and Pacific (baked or broiled)	41	60	1.07	107	46.8	0.53	0.397	4.800
Lobster, Atlantic (boiled or steamed)	72	61	0.39	35	42.7	2.92	0.077	-
Mackerel, Atlantic (baked or broiled)	75	15	1.57	97	51.6	0.94	0.460	2.600
Oysters, Pacific (boiled or steamed)	100	16	9.20	44	154.0	33.24	0.090	8.000
Rainbow trout, farmed (baked or broiled)	68	86	0.33	32	15.0	0.49	0.396	6.390
Salmon, Atlantic, farmed (baked or broiled)	63	15	0.34	30	41.4	0.43	0.647	6.800
Salmon, Pacific sockeye, wild (baked or broiled)	87	7	0.55	31	37.8	0.51	0.219	22.600
Shrimp, mixed species (boiled or steamed)	195	39	3.09	34	39.6	1.56	0.127	tr
Snow crab (boiled or steamed)	71	33	2.88	63	44.4	3.59	0.173	-
Tuna, canned, light (in water, drained, unsalted)	30	11	1.53	27	80.4	0.77	0.350	0.920
Tuna, canned, white (in water, drained, unsalted)	42	14	0.97	33	65.7	0.48	0.217	2.000
BEEF
Ground beef (lean, broiled, well done)	81	14	2.60	22	22.4	6.90	0.190	0.600
Roast beef (boneless eye of round roast, 3mm trim, roasted)	66	7	2.02	26	25.7	6.76	0.290	0.600
Top sirloin (steak, 3 mm trim, broiled)	69	7	2.70	27	26.9	6.40	0.380	0.600
PORK
Cured ham (boneless, regular, roasted)	59	8	1.34	22	19.8	2.47	0.310	0.300
Pork loin (boneless rib roast, roasted)	81	6	1.10	26	40.3	3.10	0.480	0.500
Ground fresh pork (medium, pan-fried)	88	11	1.10	25	35.4	2.90	0.270	0.700
POULTRY
Chicken breast, meat and skin (roasted)	76	12	1.26	20	-	1.45	0.350	0.200
Chicken breast, meat only (roasted)	75	13	1.08	23	-	0.78	0.540	0.200
Turkey, meat only (roasted)	76	25	1.78	26	36.8	3.10	0.460	0.300
Turkey, ground (cooked)	102	25	1.93	24	37.2	2.86	0.390	1.000

Source: Canadian Nutrient File, 2007b, March 2008. The nutrient content of the foods shown is an average and will vary somewhat according to the species, source and other factors.
^a - Total 18:3 fatty acid (includes omega-3 [alpha-linolenic acid] and omega-6 [gamma-linolenic acid])
- No data available
tr - trace
DHA Docosahexaenoic acid (22:6n-3)
EPA Eicosapentaenoic acid (20:5n-3)
ALA Alpha-linolenic acid (18:3n-3)

Notes:

• The nutrients chosen for comparison are consistent with those used by the Institute of Medicine expert committee for a similar chart in its report, Seafood Choices: Balancing Benefits and Risks (pages 46-47), with the addition of vitamin D, magnesium and cholesterol. Additional nutrients were not compared because (as indicated in the IOM seafood report, page 201), the U.S. Dietary Guidelines Advisory Committee (2005; part D, section 4, page 27) had previously concluded that the substitution of two servings of seafood for two servings of animal protein foods would not have a substantial impact on the vitamin and mineral content of the average American consumer's diet.
• The cuts of meat (beef, pork, poultry) presented for comparison were chosen to be similar to the cuts used in the chart in the IOM seafood report (pages 46-47).

Are Canadians Meeting the Recommendations?

Canada's Food Guide recommends that Canadians eat at least two Food Guide Servings of fish each week. That's about 150 grams of cooked fish (or about 5 ounces or 1 cup) each week.

Many Canadians don't seem to be hitting the mark when it comes to seafood, and could be missing out on the nutritional benefits as a result.

• Canadians are eating about 100 grams of fish per week, or 1.4 Food Guide Servings.(1)
• Most Canadians (83%) aged 1 to 55 years report eating seafood less than twice per week. For the entire population surveyed, seafood was consumed an average of 5 times over a 1-month period, or about 1-1/4 times per week.(2)
• In the Canadian Community Health Survey, 93.6% of Canadians reported eating no fish on the day of the survey.(3)
• Females aged 14 to 18 years, and females and males 71+ years, consume fewer servings from the Meat and Alternatives food group-the food group that includes seafood-than is recommended by Canada's Food Guide for their respective age and gender groups.(4)

Insights from data on the U.S. population

Data on the U.S. population-often used when Canadian data are not available because of the similarities in the food supply-reinforce these findings:

• Average quantities of seafood consumed by the general U.S. population, and by several specific population groups, are below levels suggested by many authoritative groups, including levels recommended by the American Heart Association for cardiovascular disease prevention.(5)
• Average quantities of the long-chain omega-3 fats EPA and DHA consumed by the general U.S. population, and by several specific population groups, are also below levels recommended by many authoritative groups (~250 to 500 mg/day).(6)
  
  For example, based on data from the 1999-2002 U.S. National Health and Nutrition Examination Survey:
  - Mean dietary levels for the American population are estimated to be 35 mg of EPA and 68 mg of DHA per day, for a total of 103 mg/day.
  - None of the age-sex groups had average intakes of even 200 mg per day of EPA and DHA combined.

References and details:

1. Statistics Canada: Food Statistics 2006. Cat no. 21-020-XIE. May 28, 2007 
   www.statcan.ca/bsolc/english/bsolc?catno=21-020-X&CHROPG=1
   
   The estimate shown is calculated from Statistics Canada's data indicating that Canadians ate an estimated 5.3 kg of fish per person in 2006. That figure is based on adjusted per capita disappearance data that takes into account estimated losses during processing or storage as well as an experimental adjustment for losses at the retail or consumer level, or unconsumed food, to better approximate actual consumption.
   
   
2. Health Canada: "Fish Consumption: Review and Recommendation of Current Intake Figures for Canadian Consumers." Health Canada, Bureau of Chemical Safety, 2004. (Included as Appendix IV of the Health Canada report, Human Health Risk Assessment of Mercury in Fish and Health Benefits of Fish Consumption, 2007.)
   www.hc-sc.gc.ca/fn-an/pubs/mercur/merc_fish_poisson_e.html#appd
   
   The data come from a comprehensive national 1991 Market Facts survey commissioned by Health Canada. Athough dated, this was considered the most recent and comprehensive source of Canadian fish consumption information when Health Canada reviewed the available data in 2004.
   
   
3. Canadian Community Health Survey Cycle 2.2, Nutrition (2004): Mean servings and serving distribution of fish, Canada, 2004. Health Canada, personal communication, October 2007
   
   CCHS 2.2 is the first national data on Canadians' food and nutrient intakes to be available in 35 years. Surveys based on 24-hour recall information do not capture normal variations in an individual diet and only capture information on the foods eaten on the survey day; more people are likely to eat fish over the course of a week or month.
   
   
4. Garriguet D: Nutrition: Findings from the Canadian Community Health Survey-Overview of Canadians' Eating Habits 2004, Statistics Canada Catalogue no. 82-620-MIE No. 2, 2006
   www.statcan.ca/english/research/82-620-MIE/2006002/findings.htm
   
   In this research paper by Garriguet, the comparison was based on the 1992 Food Guide, but for the present resource the data were reviewed in terms of number of grams and compared with the current quantitative Food Guide recommendations for Meat & Alternatives issued in 2007.
   
   
5. Nesheim MC, Yaktine AL (eds.): Seafood Choices: Balancing Benefits and Risks. Committee on Nutrient Relationships in Seafood Selections to Balance Benefits and Risks, Institute of Medicine, Food and Nutrition Board. Washington DC: National Academies Press, 2007 (www.nap.edu/catalog/11762.html), pages 59-60
   
   
6. Nesheim MC, Yaktine AL (eds.): Seafood Choices: Balancing Benefits and Risks, page 49 (reporting data from NHANES 1999-2002)