Seafood and Health

What Are the Health Benefits of Eating Seafood?

Much research has highlighted the role of seafood, and the long-chain omega-3 fats in seafood (EPA and DHA), in an array of potential health benefits. The rate of research has accelerated over the past several years-it's important to understand where these findings fall on the research continuum. In this section we've separated the consistent, well-substantiated benefits from the areas where the evidence for benefits is either inconsistent (when there's low agreement between studies) or insufficient (when there are too few studies to draw conclusions).

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, and 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. Specifically, 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 children.

Inconsistent or Insufficient Evidence for Benefits

Although a lot of other exciting research is underway, in many areas there's low agreement between studies, too few studies, or the studies have been conducted using supplements rather than seafood in the diet.

At this point the evidence remains inconclusive on the relationship between:

• Seafood or fish oil consumption and protection against further cardiovascular events in individuals with a history of myocardial infarction.
• Seafood or fish oil consumption and improved blood pressure, stroke, cancer, asthma, type 2 diabetes, Alzheimer's disease, or depression outcomes in adults.
• Seafood or fish oil consumption and the prevention or treatment of attention deficit hyperactivity disorder (ADHD), other behavioural disorders, or asthma in children.

Research into many more areas is just at the exploratory stage.

Evidence Behind the Canada's Food Guide Recommendation for Fish

Canada's Food Guide defines and promotes healthy eating for Canadians. By eating the recommended amounts and types of food and following the tips found in the Food Guide, Canadians can meet their nutrient needs and reduce their risk of nutrition-related chronic diseases.

The recommended amounts and types of foods in Canada's Food Guide reflect the results of a food intake pattern developed using a modelling process, a review of associations between food and chronic disease, and input received during stakeholder consultation.

• A statistical computer modelling process was used to ensure adequate intakes of nutrients as defined by the nutrient standards called Dietary Reference Intakes (DRIs). The DRIs summarize research findings about the amount of each nutrient and calories needed for good health and the prevention of chronic disease, while avoiding the negative effects of consuming too much of any individual nutrient.
• A review of the evidence on foods and risk of chronic disease was undertaken to provide additional information to develop the food intake pattern. Specifically, the Joint WHO/FAO report on Diet, Nutrition and the Prevention of Chronic Diseases, (including the background papers in the journal Public Health Nutrition), the 2005 U.S. Dietary Guidelines Advisory Committee report, and the report of the U.K. Scientific Advisory Committee on Nutrition were reviewed for evidence on the association of food and chronic disease risk. The results of this review revealed convincing evidence of the relationships between consumption of fish, particularly fatty fish, and reduced risk of cardiovascular disease.

To learn more:

On this website

• International Context-Recommendations of Authoritative Health Groups

Other resources

Food Guide development

• Canada's Food Guide: The Evidence Base
  www.hc-sc.gc.ca/fn-an/food-guide-aliment/context/evid-fond/evidence-fondements_e.html
• Katamay SW, Esslinger KA, Vigneault M et al.: Eating Well with Canada's Food Guide (2007): development of the food intake pattern. Nutr Rev 2007;65(4):155-166.
  www.hc-sc.gc.ca/fn-an/pubs/fd_int_pat-ela_mod_alim_e.html

Dietary Reference Intakes

• Institute of Medicine: Dietary Reference Intakes for Energy, Carbohydrate, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. (2002)
  www.nap.edu/books/0309085373/html/
• 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

Reports and publications on food and chronic disease

• Joint WHO/FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases (2003) 
  www.who.int/dietphysicalactivity/publications/trs916/en/
• (U.S.) 2005 Dietary Guidelines Advisory Committee report (2005) - section on fats
  www.health.gov/dietaryguidelines/dga2005/report/HTML/D4_Fats.htm or www.health.gov/dietaryguidelines/dga2005/report/PDF/D4_Fats.pdf
• (U.K.) Scientific Advisory Committee on Nutrition/Committee on Toxicology (2005)
  www.food.gov.uk/multimedia/pdfs/fishreport2004full.pdf
• Harvard Center for Risk Analysis - articles published in Am J Prev Med 2005;29(4)

Additional information on seafood and health

• 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

Current Evidence on Potential Health Benefits of Seafood

Growing evidence suggests that seafood consumption, and its associated contribution of the omega-3 fats EPA and DHA, has important health benefits. For example, DHA is known to support the normal development of the brain, eyes and nerves.

By themselves, EPA and DHA do not account for all of the health benefits associated with regularly eating seafood. As an 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 heart health benefits.

The most comprehensive recent systematic review of the evidence was undertaken by an expert committee convened by the Institute of Medicine (IOM) and released in October 2006: Seafood Choices: Balancing Benefits and Risks (2007). The IOM acts as an advisor to the U.S. federal government and as such serves as an authoritative source for evidence-based information to inform health policy.

The IOM committee reviewed the existing literature on seafood consumption and EPA/DHA supplementation. A broad range of study designs, study populations, exposures and outcomes was considered. The committee evaluated and judged the strength of the evidence for both health benefits and risks; in many cases, the evidence for health benefits was deemed too insufficient or preliminary to make recommendations (IOM seafood report, page xi). Quantitative summary of the seafood benefit/risk trade-offs was not possible; therefore, the committee developed a qualitative approach adapted from previous work to evaluate and balance benefits and risks and derive specific guidance for seafood consumption for the population as a whole and, as appropriate, for specific target populations (IOM seafood report, pages 2-3).

This section presents evidence on heart health benefits, benefits to women, infants and young children, and other areas of research in adults from the following sources:
- The report of the Institute of Medicine expert committee (2007)
- The report of the U.S. Dietary Guidelines Advisory Committee (2005)
- Primary studies (identified through a systematic literature search; published since the IOM seafood report was released in October 2006)

Overview

More detailed summary
- Heart Health Benefits
- Benefits to Women, Infants and Young Children
- Other Areas of Research in Adults

Current Evidence on Potential Health Benefits of Seafood
—Overview

Heart Health Benefits

Consistent evidence

Currently, the evidence consistently suggests that eating seafood supports heart health in the general population:

• "Observational evidence suggests that increased seafood consumption is associated with a decreased risk of cardiovascular deaths and cardiovascular events in the general population." (IOM seafood report, pages 5, 106; emphasis added)

Inconsistent or insufficient evidence

The evidence for heart health benefits in individuals at increased risk for cardiovascular disease is inconsistent:

• "Evidence is inconsistent for protection against further cardiovascular events in individuals with a history of myocardial infarction from consumption of EPA/DHA-containing seafood or fish-oil supplements." (IOM seafood report, pages 5, 106; emphasis added)

Benefits to Women, Infants and Young Children

Consistent evidence

Currently, the evidence consistently suggests that maternal seafood or fish-oil consumption during pregnancy and/or breastfeeding supports improved pregnancy outcomes:

• Observational and experimental studies have "shown an association between increased duration of gestation and intake of seafood or fish-oil supplements" during pregnancy. (IOM seafood report, pages 4-5, 89; emphasis added)
• "Evidence that the infants and children of mothers who consume seafood or EPA/DHA supplements during pregnancy and/or lactation may have improved developmental outcomes is also supported largely by observational studies." (IOM seafood report, pages 5, 89-90; emphasis added)

There is additional evidence for improved neurological outcomes in infants and young children from studies that provided omega-3 fatty acids through infant formula rather than through seafood consumption during pregnancy and/or breastfeeding:

• Experimental trials have found benefits for infant and child neurological development when DHA is provided directly to human infants through infant formula. "Visual acuity has been measured in the most trials and is increased by DHA supplementation, with preterm infants more likely to benefit than term infants. Cognitive benefits of postnatal DHA supplementation with formula have also been found in infancy and early childhood." (IOM seafood report, page 90; emphasis added)

Inconsistent or insufficient evidence

"Increased EPA/DHA intake by pregnant and lactating women is associated with increased transfer to the fetus and breastfed infant." However, "insufficient data are available to define an ideal level of EPA/DHA intake from seafood in pregnant and lactating women." (IOM seafood report, page 90)

Other Areas of Research in Adults

Inconsistent or insufficient evidence

Currently, there is neither consistent nor sufficient evidence for other health benefits and seafood consumption in adults:

• "Evidence for a benefit associated with seafood consumption or fish-oil supplements on blood pressure, stroke, cancer, asthma, type II diabetes, or Alzheimer's disease is inconclusive. Whereas observational studies have suggested a protective role of EPA/DHA for each of these diseases, supportive evidence from randomized clinical trials is either nonexistent or inconclusive." (IOM seafood report, pages 5, 106; emphasis added)

Exploratory Research

Research on seafood consumption and other health outcomes is still very preliminary. For example, exploration of the relationships between seafood or omega-3 fatty acid consumption and Parkinson's disease, macular degeneration, schizophrenia and inflammatory or autoimmune diseases like rheumatoid arthritis, lupus, Crohn's disease and psoriasis is underway. A review of this research was beyond the scope of this resource.

To learn more:

On this website

More detailed summary

• Heart Health Benefits
• Benefits to Women, Infants and Young Children
• Other Areas of Research in Adults

Other resources

• 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

Heart Health Benefits

Institute of Medicine report, - Seafood Choices: Balancing Benefits and Risks (2007)
U.S. Dietary Guidelines Advisory Committee report, Dietary Guidelines for Americans (2005)
Systematic review of primary studies published since the IOM seafood report

Institute of Medicine report, Seafood Choices: Balancing Benefits and Risks (2007)
-Findings, Guidance, and Methods

The IOM expert committee conducted a comprehensive review of the existing literature on cardiovascular benefits of seafood consumption and EPA/DHA supplementation. The committee evaluated the strength of the evidence and qualitatively summarized individual study findings in its report. Specific guidance was developed for the population as a whole and, as appropriate, for specific target populations.

Heart Health Benefits in the General Population (Primary Prevention)
Heart Health Benefits in Individuals at Increased Risk for Cardiovascular Disease (Secondary Prevention)
More Detailed Findings and Methods

Heart Health Benefits in the General Population (Primary Prevention)

Primary prevention studies refer to those carried out in subjects who are representative of the general population.

IOM Findings on Primary Prevention of Heart Disease
IOM Consumption Guidance for Primary Prevention of Heart Disease
More Detailed Findings and Methods

IOM Findings on Primary Prevention of Heart Disease (pages 106-107)
Based on its review of the evidence, the IOM expert committee found that for the general population:

• "Observational evidence suggests that increased seafood consumption is associated with a decreased risk of cardiovascular deaths and cardiovascular events in the general population. Evidence is insufficient to assess if this association is mediated through an increase in EPA and DHA consumption and/or a decrease in saturated fat consumption and/or other correlates of seafood consumption."
• "Experimental studies of the effect of EPA/DHA supplements on cardiovascular mortality or cardiovascular disease have not been conducted in the general population."
• "Based on the three recent meta-analyses of observational studies, there appears to be a linear association between seafood consumption and primary prevention of cardiovascular disease. The committee did not find strong scientific evidence to suggest a threshold of consumption, such as two servings per week, below which seafood consumption provides no benefit and above which increasing consumption provides no additional benefits."

More detail is available on the methods and studies reviewed.

IOM Consumption Guidance for Primary Prevention of Heart Disease (page 208)
Based on its findings, the IOM committee states that:

"Adolescent males, adult males, and females who will not become pregnant:

• May reduce their risk for cardiovascular disease by consuming seafood regularly, e.g., two 3-ounce servings per week;
• Who consume more than two servings a week should choose a variety of types of seafood to reduce the risk for exposure to contaminants from a single source."

To learn more:

On this website

• Summary of Health Canada's advice on seafood consumption for Canadians

Other resources

• 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

Heart Health Benefits in Individuals at Increased Risk for Cardiovascular Disease (Secondary Prevention)

Secondary prevention studies refer to those conducted in subjects who are at increased risk of cardiovascular disease because they have already experienced a cardiac event (such as myocardial infarction).

IOM Findings on Secondary Prevention of Heart Disease
IOM Consumption Guidance for Secondary Prevention of Heart Disease

IOM Findings on Secondary Prevention of Heart Disease on Secondary Prevention of Heart Disease(page 106)
For individuals who have a history of cardiovascular disease, the IOM expert committee found based on their review of the evidence that:

• "There is mixed evidence suggesting that consumption of fish-oil supplements for individuals with a history of MI [myocardial infarction] will protect them from further coronary events. Meta-analyses have also led to mixed conclusions, with most recent analyses suggesting no benefits. Experimental evidence from in vitro and other types of mechanistic studies suggests that EPA/DHA intake should be associated with positive cardiovascular outcomes. However, this prediction has not been borne out in results of human studies."
• "Evidence is inconsistent for protection against further cardiovascular events in individuals with a history of myocardial infarction from consumption of EPA/DHA-containing seafood or fish-oil supplements. The protection evidenced by population (observational) studies has not been consistently observed in randomized clinical trials."

More detail is available on the methods and studies reviewed.

IOM Consumption Guidance for Secondary Prevention of Heart Disease Prevention of Heart Disease (page 208)
Based on its findings, the IOM committee concluded that the guidance for people at risk for cardiovascular disease (and those with a history of such disease) is not materially different from that for the more general population. Therefore, the IOM committee states that:

"Adult males and females who are at risk of cardiovascular disease:

• May reduce their risk of cardiovascular disease by consuming seafood regularly, e.g., two 3-ounce servings per week;
• Although supporting evidence is limited, there may be additional benefits from including high-EPA/DHA seafood selections;
• Who consume more than two servings a week should choose a variety of types of seafood to reduce the risk for exposure to contaminants from a single source."

To learn more:

• 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

More Detailed Findings and Methods Related to IOM's Investigation of Primary and Secondary Prevention of Heart Disease

Primary and Secondary Prevention of Heart Disease-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
Primary and Secondary Prevention
Cochrane review	1	0	1	0
Meta-analysis	3	2	1	0
Review	1	1	0	0
Primary Prevention
Meta-analysis	1	1	0	0
Review	1	1	0	0
Randomized crossover	1	0	1	0
Nested cohort	1	1	0	0
Cohort	18	12	5	1
Nested case-control	1	1	0	0
Case-control	2	2	0	0
Ecological	1	1	0	0
Secondary Prevention
Review	2	1	1	0
Randomized controlled	9	5	2	2
Case-control	3	3	0	0

Primary prevention studies refer to those carried out in subjects who are representative of the general population.

Secondary prevention studies refer to those conducted in subjects who are at increased risk of cardiovascular disease because they have already experienced a cardiac event (such as myocardial infarction).

Evidence for heart health benefits in the general population (primary prevention)
Evidence for heart health benefits in individuals at increased risk for cardiovascular disease (secondary prevention)

Evidence for heart health benefits in the general population (primary prevention)
At the time the IOM expert committee report was published, only one randomized trial had been done in subjects who are representative of the general population. This is likely because the number of expected cardiovascular events would be low, thus requiring large sample sizes and/or long follow-up periods that are not practical. (IOM seafood report, pages 92-93)

The exposure of interest in the primary prevention studies tended to be seafood consumption; 21 of 23 primary studies (not including the ecological study) assessed seafood rather than other sources of omega-3 fatty acids. The randomized crossover trial and the nested case-control study measured biomarkers of omega-3 fatty acid intake. The main outcomes in the primary prevention studies tended to be cardiovascular events, such as cardiac death or non-fatal myocardial infarction.

Of the 23 primary studies, 16 (13 cohort, 2 case-control and 1 nested case-control) found evidence for a heart health benefit in individuals representative of the general population. One cohort study found evidence for a negative effect of increased seafood consumption; as seafood consumption increased, the risk of fatal or nonfatal acute myocardial infarction also increased.

Evidence for heart health benefits in individuals at increased risk for cardiovascular disease (secondary prevention)
The exposure in the secondary prevention studies tended to be omega-3 fatty acid supplements rather than seafood consumption. The intervention in six of nine randomized controlled trials (RCTs) was a DHA/EPA supplement; the remaining three RCTs evaluated dietary advice. All three case-control studies assessed exposure to seafood. Similar to the primary prevention studies, the outcomes in the secondary prevention studies tended to be cardiovascular events; however, a range of markers of cardiovascular disease, such as revascularization, tachycardia, plasma fibrinogen or triglycerides, were also assessed.

Five of 12 primary studies, all RCTs, found evidence of reduced cardiovascular disease with increased omega-3 fatty acids. Two RCTs found evidence of increased cardiovascular disease in subjects receiving either dietary advice or omega-3 fatty acid supplements.

To learn more:

• 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

U.S. Dietary Guidelines Advisory Committee report, Dietary Guidelines for Americans (2005)
-Findings, Guidance, and Methods

The Dietary Guidelines for Americans report provides science-based advice to promote health and to reduce risk for major chronic diseases through diet and physical activity. Recommendations are developed by an expert Dietary Guidelines Advisory Committee (DGAC).

DGAC Findings on Heart Health Benefits
DGAC Consumption Guidance for Heart Health Benefits
DGAC Methods for Investigating Heart Health Benefits

DGAC Findings on Heart Health Benefits

Based on its review of the evidence, the DGAC concluded that:

• "Overall the evidence from the primary and secondary prevention studies supports the hypothesis that the consumption of n-3 fatty acids (EPA, DHA, alpha-linolenic acid), fish, and fish oil reduces all-cause mortality and various CVD outcomes. These outcomes include sudden death and cardiac death (coronary or myocardial infarct (MI) death)." (DGAC report, page 25)
• "A conservative estimate is that two servings of fish high in n-3 fatty acids per week may reduce the risk of coronary death, primarily sudden death, by as much as 30 percent... among adults." (DGAC report, page 28)
• "Fish is recommended rather than supplements because epidemiologic and some RCT [randomized controlled trial] data demonstrate benefits of fish; it is a good source of n-3 fatty acids and many other nutrients; and it is low in calories and saturated fatty acids." (DGAC report, page 28)

DGAC Consumption Guidance for Heart Health Benefits

Based on its findings, the DGAC provided the following guidance:

• "The consumption of two servings (approximately 8 ounces) per week of fish high in EPA and DHA is associated with reduced risk of both sudden death and CHD death in adults. To benefit from the potential cardioprotective effects of EPA and DHA, the weekly consumption of two servings of fish, particularly fish rich in EPA and DHA, is suggested. Other sources of EPA and DHA may provide similar benefits; however, further research is warranted." (DGAC report, page 22)
• "There is some evidence that consuming more than two servings of fish per week may confer further cardioprotective effects." ...However, the evidence is insufficient to suggest an optimal quantity of fish and of omega-3 fatty acids to consume. (DGAC report, pages 25-26)

DGAC Methods for Investigating Heart Health Benefits

For the 2005 report, the DGAC systematically reviewed the scientific evidence, including meta-analyses, experimental and observational studies. The committee placed the greatest emphasis on results from cohort studies and trials with well-accepted, clinically relevant outcomes.

The evidence for seafood consumption and heart health was based on an analysis of experimental and observational studies of the cardioprotective effects of fish consumption among healthy populations and information from the 2004 evidence-based report from the Agency for Healthcare Research and Quality (AHRQ) entitled Effects of Omega-3 Fatty Acids on Cardiovascular Disease. The 2002 report on Dietary Reference Intakes for Energy Carbohydrate, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids provided the starting point for the examination of the evidence. (DGAC report, page 24)

In the DGAC report, findings of the individual studies were highlighted and summarized but not comprehensively presented; thus, a more detailed summary of findings of the individual studies that the committee reviewed is not possible here.

To learn more:

• (U.S.) 2005 Dietary Guidelines Advisory Committee report (2005) - section on fats
  www.health.gov/dietaryguidelines/dga2005/report/HTML/D4_Fats.htm or www.health.gov/dietaryguidelines/dga2005/report/PDF/D4_Fats.pdf
• Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health & Human Services, systematic reviews on omega-3 fatty acids (2004-2005)
  www.ahrq.gov/clinic/epcquick.htm#Otopics
• Wang C, Chung M, Lichtenstein A et al:. Effects of Omega-3 Fatty Acids on Cardiovascular Disease. Evidence Report/Technology Assessment No. 94. (Prepared by the Tufts-New England Medical Center Evidence-based Practice Center, Boston, MA.) AHRQ Publication No.04-E009-2. Rockville, MD: Agency for Healthcare Research and Quality. March 2004.
  www.ahrq.gov/clinic/epcsums/o3cardsum.htm (summary)
  www.ahrq.gov/downloads/pub/evidence/pdf/o3cardio/o3cardio.pdf (full report)
• Institute of Medicine: Dietary Reference Intakes for Energy, Carbohydrate, Fibre, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. (2002)
  www.nap.edu/books/0309085373/html/

Systematic review of primary studies published since the IOM seafood report
-Findings and Method

A search of the scientific literature for relevant primary studies on potential heart health benefits published since the release of the Institute of Medicine's Seafood Choices report found 142 potential studies, only two of which were suitable for inclusion. The findings of those two studies are summarized here.

Findings of Recent Studies on Heart Health Benefits
Method for Literature Search on Heart Health Benefits

Findings of Recent Studies on Heart Health Benefits

Of 142 potential studies that have been published since the release of the Institute of Medicine Seafood Choices report, only two studies met the criteria for inclusion. The articles were reviewed and evaluated; the following table summarizes the characteristics and findings of these studies.

Reference	Aim of Study	Design	Sample Characteristics	Exposure and Duration	Diet Assessment Tool	Changes in Health/ Biomarker and Adverse Effects
Jarvinen et al. 2006	To investigate "the relationships between the consumption of fish and fish-specific fatty acids and the risk of CHD"	Cohort (prospective) (1966-1972)	-Finland -Men and women (n=5,220) -30 to 79 years -Free of CHD at baseline -Mean follow-up 21.5 years	Fish consumption during the previous year	Diet history assessment interview method	Increased seafood consumption was associated with decreased coronary heart disease mortality in women but not men -Women RR 0.59; 95% CI 0.36-0.99; p for trend 0.02 -Men RR 1.00; 95% CI 0.70-1.43; p for trend 0.83
Lockheart et al. 2007	To "...describe dietary patterns and their association with first myocardial infarction (MI)...".	Case-control (retrospective) (1995-1997)	-Norway -Men and post-menopausal women -45 to 75 years -Cases where the MI event was their first (i.e. no history of previous MI or other serious disease) -218 recruited, 211 included in final sample (106 cases and 105 controls) -Controls were matched for age, sex and location	Fish consumption during the previous year	Food frequency questionnaire* -Validated in Norwegian men and postmenopausal women	High-fat fish intake was greater in controls than in myocardial infarct cases (OR 0.57; 95% CI 0.38-0.86). High-fat fish consumption included supplemental cod-liver oil, which was consumed by 42% of the sample.

CI = confidence interval; MI = myocardial infarct; OR = odds ratio; RR = relative risk
*Note: Food frequency questionnaires (FFQs) are designed to measure usual long-term dietary intake; as a result they tend to be imprecise with respect to actual intake. To reduce the likelihood that an FFQ will misclassify an individual's exposure status, an FFQ should be validated for the specific study population (i.e. Norwegian men and postmenopausal women) and exposure of interest (i.e. seafood consumption).

• In the cohort study (Jarvinen et al. 2006), the relative risk of coronary heart disease mortality between the highest and lowest intake quintiles of fish intake was significant in women but not men when adjusted for age, energy intake, geographical area, BMI, serum cholesterol, blood pressure, smoking, occupation and diabetes. Although consumption of dietary supplements was not accounted for, the authors reported that use of such supplements was uncommon in Finland at the time of the baseline study.
  
  The finding among women is consistent with the suggested beneficial effects of fish consumption against developing coronary heart disease (CHD). Only a few previous previous prospective studies on fish consumption and CHD risk have been reported on women. The authors commented that the lack of an inverse association between fish consumption and CHD risk among men is consistent with the results of previous studies on fish consumption and CHD in middle-aged Finnish men who had a high level of general CHD risk factors. Thus, this study adds to the body of evidence reviewed by the IOM committee, supporting a positive association of fish consumption and reduced risk of CHD.
  
• In the case-control study (Lockheart et al. 2007), high-fat fish intake was greater in controls than in myocardial infarct (MI) cases. While this suggests a heart health benefit with seafood consumption, which is consistent with the conclusions of the IOM seafood report, the results should be interpreted with caution. Because diet assessment was retrospective (diet was examined by recalling intake over the year prior to subjects experiencing an MI), it is possible that the occurrence of a myocardial infarction biased cases' recall of their seafood consumption. Furthermore, consumption of cod-liver oil was included in the estimate of seafood consumption, so it may be that some of the benefit was due to supplementation rather than diet.

Method for Literature Search on Heart Health Benefits

MEDLINE was searched on March 31, 2008, using the following strategy:

• Search: (Seafood[MeSH term] OR Fish[Title/Abstract]) AND Cardiovascular Diseases[MeSH term] NOT Review[Publication Type] NOT In Situ Hybridization, Fluorescence[MeSH term]
• Limits: Publication Date from 2006/04, Humans, English

The above search strategy identified 142 articles. Studies were included if the study population, exposures and outcomes matched those for which health benefits are based on consistent evidence. Only studies that met the following criteria were included:

• Main outcomes were cardiovascular events such as death or myocardial infarction (i.e. not risk factors for cardiovascular disease).
• Exposure was seafood consumption (i.e. not supplements or biomarkers).
• Subjects were not at increased risk for cardiovascular disease (i.e. not secondary prevention studies).
• Studies were not already included in the IOM seafood report.

To learn more:

• Jarvinen R, Knekt P, Rissanen H, Reunanen A: Intake of fish and long-chain n-3 fatty acids and the risk of coronary heart mortality in men and women. Br J Nutr 2006; 95: 824-829
  http://journals.cambridge.org/download.php?...
• Lockheart MS, Steffen LM, Rebnord HM et al: Dietary patterns, food groups and myocardial infarction: a case-control study. Br J Nutr 2007; 98: 380-387
  Abstract and ordering information: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1208296
• 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

Benefits to Women, Infants and Young Children

Institute of Medicine report, Seafood Choices: Balancing Benefits and Risks (2007)
Systematic review of primary studies published since the IOM seafood report

Institute of Medicine report, Seafood Choices: Balancing Benefits and Risks (2007)
-Findings, Guidance, and Method

The IOM committee conducted a comprehensive review of the existing literature on the potential benefits of seafood consumption and EPA/DHA supplementation to women, infants and young children. The committee evaluated the strength of the evidence and qualitatively summarized individual study findings in its report. Specific guidance was developed for the population as a whole and, as appropriate, for specific target populations.

IOM Findings on Benefits to Women, Infants and Young Children
IOM Consumption Guidance for Benefits to Women, Infants and Young Children
More Detailed Findings and Method

IOM Findings on Benefits to Women, Infants and Young Children

The IOM committee found that the evidence consistently suggests that eating seafood supports improved pregnancy outcomes and normal growth and development in the infants and young children:

• Observational and experimental studies have "shown an association between increased duration of gestation and intake of seafood or fish-oil supplements" during pregnancy. (pages 4-5, 89)
• "Evidence that the infants and children of mothers who consume seafood or EPA/DHA supplements during pregnancy and/or lactation may have improved developmental outcomes is also supported largely by observational studies." (pages 5, 89-90)

There is additional evidence for improved neurological outcomes in infants and young children from studies that provided omega-3 fatty acids through infant formula rather than through seafood consumption by pregnant or breastfeeding mothers:

• Experimental trials have found benefits for infant and child neurological development when DHA is provided directly to human infants through infant formula. "Visual acuity has been measured in the most trials and is increased by DHA supplementation, with preterm infants more likely to benefit than term infants. Cognitive benefits of postnatal DHA supplementation with formula have also been found in infancy and early childhood. However, the number of trials has been limited and the specific outcomes varied, precluding a systematic review." (page 90)

"Increased EPA/DHA intake by pregnant and lactating women is associated with increased transfer to the fetus and breastfed infant." However, "insufficient data are available to define an ideal level of EPA/DHA intake from seafood in pregnant and lactating women." (page 90)

More detail is available on the methods and studies reviewed.

IOM Consumption Guidance for Benefits to Women, Infants and Young Children

Based on these findings, the IOM committee concluded that: (page 207)

"Females who are or may become pregnant or who are breastfeeding:

• May benefit from consuming seafood, especially those with relatively higher concentrations of EPA and DHA;
• A reasonable intake would be two 3-ounce (cooked) servings but can safely consume 12 ounces per week."

Children up to age 12:

• May benefit from consuming seafood, especially those with relatively higher concentrations of EPA and DHA;
• A reasonable intake would be two 3-ounce (cooked), or age appropriate, servings but can safely consume 12 ounces per week."

The IOM committee also included guidance for these groups on species to limit or avoid based on mercury content.

To learn more:

On this website

• Summary of Health Canada's advice on seafood consumption for Canadians

Other resources

• 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

More Detailed Findings and Methods
Related to IOM's Investigation of Benefits to Women, Infants and Young Children

The following chart presents summary comments on benefits to women, infants and young children, compiled from the IOM committee's seafood report. For each area of investigation, a link is provided to a more detailed evidence summary which is important for interpreting these comments.

Area of Investigation	Summary Comments Extracted from the IOM Committee's Qualitative Summary of the Evidence
Preeclampsia in Women	Because the research "did not show clear evidence of a beneficial effect of a broad range of intake (or biochemical indicators) of EPA/DHA levels, it does not appear likely that increased seafood intake or fish-oil supplementation will reduce the incidence of preeclampsia among US women." (page 71)
Postpartum Depression in Women	"The committee cannot draw a conclusion about the effect of increased EPA/DHA on postpartum depression. Thus, there is not sufficient evidence to conclude that the health of pregnant or lactating women will benefit directly from an increase in seafood intake." (page 73)
Duration of Gestation and Birth Weight in Infants	"Observational studies suggest and several experimental studies support that EPA/DHA supplementation or higher seafood intake is associated with an increased duration of gestation." (page 77)
Development in Infants and Children	"Observational and experimental studies offer evidence that maternal DHA intake can benefit development of the offspring; however, there are large gaps in knowledge that need to be filled by experimental studies." (page 84) "The strongest evidence of benefit for postnatal DHA supplementation in formula-fed preterm and term infants is higher visual acuity, an outcome that has been measured repeatedly in clinical trials... Results of some experimental trials suggest that postnatal DHA infant formula supplementation benefits cognitive function as well." (page 88)
Allergy in Infants and Children	"These findings do not provide strong support for the hypothesis that exposure to omega-3 fatty acids from fish oil in utero or through breast milk could decrease the incidence of wheezing and atopic disease in early childhood." (page 84) "Neither can any conclusions yet be drawn about the possible role of seafood or EPA/DHA supplementation in the prevention of asthma" in children. (page 89)
ADHD in Children	"Few randomized trials have been carried out to test whether EPA/DHA supplementation in children reduced symptoms of ADHD, and there is little evidence for benefits." (page 89)

Evidence Related to Preeclampsia in Women
The following table summarizes the number of studies the IOM committee reviewed in women on preeclampsia risk during pregnancy and seafood or omega-3 fatty acid intake. The most common outcome measures were blood pressure or diagnosis of preeclampsia, which included proteinurea and pregnancy-induced hypertension.

Preeclampsia in Women-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Review	1	0	1
Randomized controlled	5	1	4
Controlled	1	1	0
Cohort	1	0	1
Nested case-control	1	0	1
Case-control	3	3	0

Of 11 primary studies, only one (a nested case-control study) measured exposure to seafood; no evidence for reduced risk of preeclampsia was found. The remaining studies assessed other dietary sources of omega-3 fatty acids, omega-3 fatty acid supplements, or biomarkers of EPA/DHA consumption. Five of 11 primary studies showed evidence for reduced risk of preeclampsia with increased omega-3 fatty acids; two considered omega-3 fatty acid supplements (one a randomized controlled trial and the other a controlled trial with no randomization), and three were case-control studies that assessed biomarkers of omega-3 fatty acid intake.

Based on its review of the evidence, the IOM committee stated that because the research "did not show clear evidence of a beneficial effect of a broad range of intake (or biochemical indicators) of EPA/DHA levels, it does not appear likely that increased seafood intake or fish-oil supplementation will reduce the incidence of preeclampsia among US women." (IOM seafood report, page 71)

Evidence Related to Postpartum Depression in Women
The following table summarizes the number of studies the IOM committee reviewed in women on postpartum depression and seafood or omega-3 fatty acid intake. The most common outcome measures were scores from postpartum depression scales or incidence of doctor-diagnosed postpartum depression.

Postpartum Depression in Women-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Review	1	1	0
Open trial	1	0	1
Randomized controlled	1	0	1
Cohort	2	1	1
Cross-sectional	1	1	0

Two of five primary studies (one cohort and one cross-sectional) measured exposure to seafood; both showed evidence for reduced risk of postpartum depression with higher omega-3 fatty acid intake. The remaining studies assessed omega-3 fatty acid supplements or biomarkers of omega-3 fatty acid intake and found no evidence for a beneficial effect.

Based on its review of the evidence, the IOM committee stated that they "cannot draw a conclusion about the effect of increased EPA/DHA on postpartum depression. Thus, there is not sufficient evidence to conclude that the health of pregnant or lactating women will benefit directly from an increase in seafood intake." (IOM seafood report, page 73)

Evidence Related to Duration of Gestation and Birth Weight in Infants
The following table summarizes the number of studies the IOM committee reviewed in infants on duration of gestation and birth weight and maternal seafood or omega-3 fatty acid intake. The most common outcome measures were birth weight and duration of gestation; however, other measures such as birth length, head circumference, gestational age, preterm birth versus term birth, and intrauterine growth retardation were also assessed.

Duration of Gestation and Birth Weight in Infants-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
Randomized controlled	10	8	1	1
Cohort	5	4	1	0
Case-control	1	1	0	0

Two of 16 primary studies (both cohort) reported results for maternal seafood consumption. The remaining studies assessed other dietary sources of omega-3 fatty acids, omega-3 fatty acid supplements, or biomarkers of omega-3 fatty acid consumption. Thirteen of 16 primary studies (8 of 10 randomized controlled trials, 4 of 5 cohort studies and the case-control study) found evidence for an association between increased duration of gestation and/or birth weight and increased maternal seafood or omega-3 fatty acid intake. One randomized controlled trial found that omega-3 fatty acid supplements were associated with lower birth weight.

Based on its review of the evidence, the IOM committee stated that "observational studies suggest and several experimental studies support that EPA/DHA supplementation or higher seafood intake is associated with an increased duration of gestation." (IOM seafood report, page 77)

Evidence Related to Development in Infants and Children
The following table summarizes the number of studies the IOM committee reviewed in infants on infant development and seafood or omega-3 fatty acid intake, including seafood or omega-3 fatty acids from a) maternal intake during pregnancy or b) infant formula or breastmilk. The most common developmental outcomes included were measures of visual acuity or cognitive development.

Development in Infants and Children-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association		Evidence of an adverse effect
Maternal seafood or omega-3 fatty acid supplement intake during pregnancy
Review	4	4	0	0
Randomized controlled	2	1	1	0
Cohort	7	6	1	0
Case-control	1	1	0	0
Cross-sectional	1	1	0	0
Animal	4	3	0	1
Omega-3 fatty acid intake from supplemented infant formula or from breastmilk
Cochrane review	2	0	2	0
Meta-analysis	2	2	0	0
Review	8	8	0	0
Randomized controlled	31	20	10	1
Cohort	2	2	0	0
Animal	4	3	1	0

a) Infant development and maternal seafood or omega-3 fatty acid supplement intake during pregnancy

Four of 11 primary studies (three cohort and one case-control) in humans measured seafood consumption. The remaining studies assessed other dietary sources of omega-3 fatty acids, omega-3 fatty acid supplements, or biomarkers of EPA/DHA consumption. Nine of 11 primary studies (one of two randomized controlled trials, six of seven cohort studies, the case-control study and the cross-sectional study) found evidence for improved developmental outcomes in infants of mothers with increased seafood or omega-3 fatty acid intake. Of note, all four studies (three cohort and one case-control) that measured seafood consumption found evidence for positive effects.

Based on its review of the evidence from studies on maternal intake of seafood or omega-3 fatty acid supplements, the IOM committee stated that "Observational and experimental studies offer evidence that maternal DHA intake can benefit development of the offspring; however, there are large gaps in knowledge that need to be filled by experimental studies." (IOM seafood report, page 84)

b) Infant development and omega-3 fatty acid intake from supplemented formula or from breastmilk

Twenty-eight of 33 primary studies in humans examined omega-3 fatty acids in infant formula. The remaining five studies assessed the effects of breastmilk from mothers who consumed omega-3 fatty acids through diet or supplements. Twenty-two of 33 primary studies (20 of 31 randomized controlled trials and both cohort studies) in humans showed evidence of improved developmental outcomes with increased seafood or omega-3 fatty acid intake. One randomized controlled trial found that increased omega-3 fatty acid intake was associated with lower vocabulary comprehension scores.

Based on its review of the evidence from studies on omega-3 fatty acid intake from supplemented formula or from breastmilk, the IOM committee stated that "The strongest evidence of benefit for postnatal DHA supplementation in formula-fed preterm and term infants is higher visual acuity, an outcome that has been measured repeatedly in clinical trials. In addition, some positive effects have been found on cognitive function in infancy and childhood in both experimental and observational studies and in relation to both pre- and postnatal DHA intake... Results of some experimental trials suggest that postnatal DHA infant formula supplementation benefits cognitive function as well." (IOM seafood report, page 88)

Evidence Related to Allergy in Infants and Children

The following table summarizes the number of studies the IOM committee reviewed in infants and children on allergy and seafood or omega-3 fatty acid intake, including seafood or omega-3 fatty acids from a) maternal intake, b) infant formula, or c) foods other than exclusively breastmilk or formula. The most frequently measured outcomes were markers of allergy, such as cytokine response; however, direct measures of allergy or asthma, such as wheeze, eczema or food allergy, were also measured.

Allergy in Infants and Children-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
a) Maternal omega-3 fatty acid intake during pregnancy
Randomized controlled	4	3	1	0
Cohort	1	0	1	0
b) Omega-3 fatty acid intake from supplemented infant formula
Review	2	1	1	0
Randomized controlled	1	1	0	0
c) Omega-3 fatty acid intake from foods other than exclusively breastmilk or formula
Review	3	2	1	0
Randomized controlled	2	0	2	0
Case-control	2	1	0	1
Ecological	2	2	0	0

a) Infant or childhood allergy and maternal omega-3 fatty acid intake during pregnancy

None of the five primary studies that investigated the effects of increased maternal omega-3 fatty acid consumption during pregnancy examined seafood consumption. All assessed omega-3 fatty acid supplements or biomarkers of omega-3 fatty acid consumption. Three of five primary studies (all randomized controlled trials) found evidence for reduced allergy or asthma in infants and children of mothers with higher omega-3 fatty acids during pregnancy.

b) Infant or childhood allergy and omega-3 fatty acid intake from supplemented infant formula

The only primary study (a randomized controlled trial) that assessed exposure to omega-3 fatty acids from infant formula found evidence for reduced allergy.

Based on its review of the evidence from studies of maternal intake or intake from infant formula, the IOM committee stated that "These findings do not provide strong support for the hypothesis that exposure to omega-3 fatty acids from fish oil in utero or through breast milk could decrease the incidence of wheezing and atopic disease in early childhood." (IOM seafood report, page 84)

c) Childhood allergy and omega-3 fatty acid intake from foods other than exclusively breastmilk or infant formula

Four primary studies (not including the ecological studies) assessed childhood allergy and omega-3 fatty acid intake. Two of the four studies were case-control studies that assessed seafood consumption. One showed evidence of reduced risk of allergy in children whereas the other found evidence for increased risk of asthma. The two randomized controlled trials found no evidence of either a benefit or adverse effect.

Based on its review of the evidence from studies of increased omega-3 fatty acid intake from foods other than exclusively breastmilk or infant formula, the IOM committee stated that "Neither can any conclusions yet be drawn about the possible role of seafood or EPA/DHA supplementation in the prevention of asthma" in children. (IOM seafood report, page 89)

Evidence Related to ADHD in Children
The following table summarizes the number of studies the IOM committee reviewed in children on attention-deficit hyperactivity disorder (ADHD) and consumption of seafood or omega-3 fatty acids. The most common outcome measures were scores from attention and hyperactivity scales; however, teacher reports and responses to various tests related to dyslexia, dyspraxia, or short-term memory were also assessed.

ADHD in Children-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
Review	1	1	0	0
Randomized controlled	5	2	2	1
Trial	1	1	0	0
Case-control	3	2	1	0

Six of nine primary studies assessed outcomes related to ADHD in children with suspected or diagnosed ADHD. All nine assessed other dietary sources of omega-3 fatty acids, omega-3 fatty acid supplements, or biomarkers of omega-3 fatty acid consumption. Five of nine primary studies (two of five randomized controlled trials, the one non-randomized trial, and two of three case-control studies) found evidence for an association between increased omega-3 fatty acids and reduced symptoms of ADHD. One randomized controlled trial found that short-term memory and errors of omission and commission were lower in the group that received increased omega-3 fatty acids.

Based on its review of this evidence, the IOM committee stated that "Few randomized trials have been carried out to test whether EPA/DHA supplementation in children reduced symptoms of ADHD, and there is little evidence for benefits." (IOM seafood report, page 89)

To learn more:

• 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

Systematic review of primary studies published since the IOM seafood report
-Findings and Method

A search of the scientific literature for relevant studies on potential benefits to women, infants and young children published since the release of the Institute of Medicine's Seafood Choices report found 214 potential studies, only five of which were suitable for review. The findings of those five studies are summarized here.

Findings of Recent Studies on Benefits to Women, Infants and Young Children
Method for Literature Search on Benefits to Women, Infants and Young Children

Findings of Recent Studies on Benefits to Women, Infants and Young Children

Of 214 potential studies that have been published since the release of the Institute of Medicine Seafood Choices report, only five studies met the criteria for inclusion. The articles were reviewed and evaluated; the following table summarizes the characteristics and findings of these studies.

Reference	Aim of Study	Design	Sample Characteristics
Neurodevelopmental outcomes
Hibbeln et al. 2007	"...to assess whether the advice [to restrict overall consumption of seafood to 340 g/wk] is successful in providing protection from adverse neuro-developmental outcomes."	Cohort (1991-1992)	-United Kingdom -Pregnant women (n=11,875) -All pregnant women living in Bristol, U.K. with a due date between Apr 1/1991 and Dec 31/1992 were eligible for inclusion
Gestation Duration and Birth Weight
Guldner et al. 2007	To "investigate the relation of seafood... intake before pregnancy to length of gestation, birthweight and decreased fetal growth..."	Cohort (2002-2005)	-France -Pregnant women (n=2,398) -Inclusion criteria were not described
Halldorsson et al. 2007	"...to examine the association between fish consumption and fetal growth [birth weight, length, head circumference] among... infants and to determine the importance of type of fish in this association by distinguishing between fatty fish and lean fish."	Cohort (1996-2002)	-Denmark -Pregnant women (n=44,824) -All pregnant women living in Denmark who were fluent in Danish were eligible -Singleton, full-term births
Haugen et al. 2008	"...to investigate if pregnant women... following a MD [Mediterranean-type diet] during the first 17-24 weeks of pregnancy had reduced risk of preterm birth."	Cohort (2002-2005)	-Norway -Pregnant women (n=40,817) -Non-smoking, BMI 19-32, aged 21-38 years, no history of >3 spontaneous abortions, energy intake between 4,200-16,700 kJ -Singleton birth
Olsen et al. 2006	To "...examine the association between exposure to seafood intake during two periods of pregnancy... and risks of preterm delivery and postterm delivery..."	Cohort (1992-1996)	-Denmark -Pregnant women (n=8,729) -All women attending antenatal care in Aarhus, Denmark were invited -Women reporting intake of fish oil supplements were excluded -Singleton birth without detected malformations

...continued

Reference	Exposure and Duration	Diet Assessment Tool	Changes in Health/ Biomarker and Adverse Effects
Neurodevelopmental outcomes
Hibbeln et al. 2007	Seafood consumption at 32 weeks' gestation	Food frequency questionnaire* -Validated for use in pregnancy -Validated for frequency of seafood consumption	Compared with higher seafood intake, low maternal seafood intake during pregnancy (<340 g/wk) was associated with adverse neurodevelopmenal outcomes in children (verbal IQ and scores for prosocial behaviour, fine motor, communication and social development at various ages between 6 months and 8 years).
Gestation Duration and Birth Weight
Guldner et al. 2007	Seafood consumption prior to pregnancy (measured during first trimester of pregnancy)	Food frequency questionnaire* -No information was provided on whether the questionnaire was validated for seafood consumption in women	The risk of small-for-gestational-age birth was decreased in women eating shellfish two times a week or more, compared with those eating fish less than once per month (OR 2.14; 95% CI 1.13-4.07). There was a small but significant improvement in length of gestation with each additional fish meal per month (0.02 week; 95% CI 0.002-0.035). No improvements were seen for birth weight or preterm birth.
Halldorsson et al. 2007	Seafood consumption (questionnaire was sent by mail at 25 weeks' gestation)	Food frequency questionnaire* -Validated for use in pregnancy	The risk for classification below the 10th percentile for fetal growth was higher in women who consumed more than 60 g fish/day compared with women who consumed 5 g or less: -Weight OR:1.24; 95% CI 1.03-1.49 -Length OR 1.20; 95% CI 1.00-1.45 -Head circumference OR 1.21 95% CI 1.01-1.43 The associations were explained entirely by fatty fish versus lean fish.
Haugen et al. 2008	Consumption of a Mediterranean-type diet during the first 17-24 weeks of pregnancy: -eat ≥2 fish servings/wk -eat ≥5 vegetable/ fruit servings/ week -eat ≤ 2 servings of meat/wk -use olive or rapeseed oil for cooking and dressings -drink ≤ 2 cups of coffee/day	Food frequency questionnaire* -Validated for use in pregnancy	Compared with seafood consumption at least once per week, zero seafood consumption during both the early and mid
Olsen et al. 2006	Seafood consumption around gestation weeks 16 and 30	Four food frequency questions* -No information was provided on whether the questions were validated for seafood consumption in women	Compared with seafood consumption at least once per week, zero seafood consumption during both the early and mid-part of pregnancy was associated with: -shorter mean gestation length (early consumption 3.91 days; 95% CI 2.24-5.58; mid consumption 3.1 days; 95% CI 1.4-4.8), and -increased pre-term delivery (early consumption OR 2.38; 95% CI 1.23-4.61; mid consumption OR 2.38 ; 95% CI 1.8-4.78)

CI = confidence interval; OR = odds ratio
*Note: Food frequency questionnaires (FFQs) are designed to measure usual long-term dietary intake; as a result they tend to be imprecise with respect to actual intake. To reduce the likelihood that an FFQ will misclassify an individual's exposure status, an FFQ should be validated for the specific study population (i.e. pregnant women) and exposure of interest (i.e. seafood consumption).

Neurodevelopment

• The findings of the cohort study that examined neurodevelopmental outcomes in infants (Hibbeln et al. 2007) add to the strength of the evidence reviewed by the IOM committee. In this study, low maternal seafood intake during pregnancy was associated with lower verbal IQ and lower scores for prosocial behaviour, fine motor skills, communication and social development in infants or children at various ages between 6 months and 8 years, in non-linear dose-response patterns. The relationships held after adjusting for differences in numerous factors related to socioeconomic differences, two perinatal factors (birth weight and gestation at delivery) and 12 food categories. The outcomes of infants of mothers who took supplements but did not eat seafood were close to those of mothers who did eat fish. The results also held when the data were reanalyzed to account for tiers of methylmercury exposure.

Duration of Gestation and Birth Weight

• The findings of three of the four cohort studies (Guldner et al. 2007; Haugen et al. 2008; Olsen et al. 2006) that assessed the association between duration of gestation and birth weight also add strength to the evidence reviewed by the IOM committee. All three studies showed increased duration of gestation, fetal growth or birth weight outcomes in infants of mothers who consumed more seafood during pregnancy.
• The remaining cohort study (Halldorsson et al. 2007) found that infants of mothers who consumed more seafood were more likely to have fetal growth measures below the 10th percentile for gestational age and gender. This contradicts the majority of the evidence reviewed by the IOM committee, as well as the two other cohort studies published since the IOM seafood report. When the analysis was stratified by type of fish, the negative effect persisted for infants of mothers who consumed fatty fish (e.g. salmon, herring, mackerel, trout, Greenland halibut) four times per month or more. The crude results for lean fish (e.g. cod, pollock, plaice, flounder, garfish) were almost the opposite of those for fatty fish; however, the associations were not statistically significant after adjustment for confounding factors. While contamination levels were not measured in this study, the authors speculate that the negative effect in this study might have been due to contamination by persistent organic pollutants in the fatty fish.

Method for Literature Search on Benefits to Women, Infants and Young Children

MEDLINE was searched on March 31, 2008, using the following strategy:

• Search: (Seafood[MeSH term] OR Fish[Title/Abstract]) AND (Pregnancy[MeSH term] OR Infant[MeSH term]) NOT Review[Publication Type] NOT In Situ Hybridization, Fluorescence[MeSH]
• Limits: Publication Date from 2006/04, Humans, English

The above search strategy identified 214 articles. Studies were included if the study population, exposures and outcomes matched those for which health benefits are based on consistent evidence. Only studies that met the following criteria were included:

• Main outcomes for women were duration of gestation or birth weight.
• Main outcomes for infants or young children were developmental outcomes (e.g. anthropometry, visual acuity, cognition).
• Exposure was seafood consumption (i.e. not supplements or biomarkers).
• Studies were not already included in the IOM seafood report.

To learn more:

• Guldner L, Monfort C, Rouget F et al: Maternal fish and shellfish intake and pregnancy outcomes: A prospective cohort study in Brittany, France. Environ Health 2007; 6:33
  www.ehjournal.net/content/6/1/33
• Halldorsson Th I, Meltzer HM, Thorsdottir I et al: Is high consumption of fatty fish during pregnancy a risk factor for fetal growth retardation? A study of 44,824 Danish pregnant women. Am J Epidemiol 2007;166(6):687-696
  Abstract and ordering information: http://aje.oxfordjournals.org/cgi/content/abstract/166/6/687
• Haugen M, Meltzer HM, Brantsaeter AL et al: Mediterranean-type diet and risk of preterm birth among women in the Norwegian Mother and Child Cohort Study (MoBa): a prospective cohort study. Acta Obstet Gynecol Scand 2008;87:319-324
  Abstract and ordering information: www.informaworld.com/smpp/content?content=10.1080/00016340801899123
• Hibbeln JR, Davis JM, Steer C et al.: Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. Lancet 2007a;369(9561):578-585
  www.thelancet.com/journals/lancet/article/PIIS0140673607602773/fulltext [accessible with free registration]
• Olsen SF, Østerdal ML, Salvig JD et al: Duration of pregnancy in relation to seafood intake during early and mid pregnancy: prospective cohort. Eur J Epidemiol 2006; 21:749-758
  Abstract and ordering information: www.springerlink.com/content/u7k548802514mk74/
• 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

Other Areas of Research in Adults

Institute of Medicine report, Seafood Choices: Balancing Benefits and Risks (2007)
-Findings, Guidance and Methods

The IOM expert committee conducted a comprehensive review of the existing literature on the potential health benefits of seafood consumption and EPA/DHA supplementation. The committee evaluated the strength of the evidence and qualitatively summarized individual study findings in its report.

IOM Findings on Other Areas of Research in Adults
IOM Guidance for Other Areas of Research in Adults
More Detailed Findings and Methods

IOM Findings on Other Areas of Research in Adults

More detail is available on the methods and studies reviewed.

IOM Consumption Guidance for Other Areas of Research in Adults

Based on its findings, the IOM committee did not develop additional guidance related to health benefits other than for heart health in adults and benefits to women, infants and young children. (IOM seafood report, page 208)

To learn more:

• 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

More Detailed Findings and Methods
Related to IOM's Investigation of Other Areas of Research in Adults

The following chart presents summary comments on other areas of research in adults, compiled from the IOM committee's seafood report. For each area of investigation, a link is provided to a more detailed evidence summary which is important for interpreting these comments.

Area of Investigation	Summary Comments Extracted from the IOM Committee's Qualitative Summary of the Evidence
Stroke	"Taken together, these observational studies provided inconclusive results for an association between seafood intake and stroke. These results suggest that seafood consumption may influence stroke risk; however, identification of mechanisms or alternate explanations for the results requires further study. The type of seafood meal, particularly the method of preparation, is not recorded in most observational studies but may be a major effect modifier." (page 98)
Lipid Profile	"In the general population, the effect from increased seafood consumption on the lipid profile is unclear. However, experimental studies of EPA/DHA supplementation at levels >1 g per day showed decreased triglyceride levels; the effect on other components of the lipid profile is less clear." (page 106)
Blood Pressure	"It is unclear from these studies whether seafood consumption, in the range consumed by most Americans, is an effective means to reduce blood pressure. Further, it is not known if the association between EPA/DHA consumption and blood pressure is linear of if there is a threshold below which no benefit is detectable." (page 101)
Arrhythmia	The IOM committee did not include a specific qualitative summary comment on the evidence for arrhythmia. (pages 101-102)
Other Cardiac Indicators	The IOM committee did not include a specific qualitative summary comment on the evidence for other cardiac indicators. (pages 102-103)
Diabetes	"Although EPA/DHA consumption has been shown to improve lipid profiles and other indicators of cardiovascular risk in those with type II diabetes, there is currently no evidence that intakes of 2-4 g/day of EPA/DHA can improve gylcemic control." (page 103)
Asthma and Allergies	The IOM committee did not include a specific qualitative summary comment on the evidence for asthma and allergies in adults. (page 103)
Cancer	"The biological functions associated with consumption of omega-3 fatty acids suggest that it may have some impact on cancer risk. Available evidence comes primarily from observational studies rather than randomized controlled trials. A small number of these studies show some protection for certain types of cancer (i.e., breast, colorectal, and lung), whereas others support an increase in risk (e.g., breast). The majority of the studies, however, conclude there is no significant effect on risk for cancer associated with seafood consumption or intake of other sources of EPA/DHA. Overall, the consumption of seafood, ALA, or EPA/DHA from all sources does not appear to decrease cancer risk." (page 104)
Age-related and Other Neurological Outcomes	"Consumption of EPA/DHA, specifically from seafood consumption, may provide some protection in terms of age-related cognitive decline as well as risk for Alzheimer's and other neurological diseases. It should be noted that... evidence for reduced risk for these diseases comes primarily from observational studies. The beneficial effects appear to be more closely related to the consumption of seafood and/or global intake of DHA rather than EPA or ALA. Overall, the evidence is tenuous and counterbalanced by a number of studies that did not find significant benefits." (page 104)

Evidence Related to Stroke
The following table summarizes the number of studies the IOM committee reviewed in adults on risk of stroke and seafood or omega-3 fatty acid intake. The most common outcome measures were incidence of stroke (ischemic and/or hemorrhagic) and total stroke mortality.

Stroke-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Cochrane review	1	0	1
Meta-analysis	2	1	1
Review	1	1	0
Cohort	10	8	2
Case-control	2	2	0
Ecological	1	1	0

All of the cohort and case-control studies measured seafood consumption. Ten of 12 cohort or case-control studies (8 of 10 cohort studies and both case-control studies) found evidence for decreased risk of stroke, particularly ischemic stroke, with increased seafood consumption. One cohort study found evidence to suggest that the type of seafood might influence risk. In that study, consumption of tuna or other baked or broiled seafood was associated with lower rates of ischemic stroke whereas fried seafood was associated with higher rates of ischemic stroke.

Based on its review of the evidence, the IOM committee stated that, "Taken together, these observational studies provided inconclusive results for an association between seafood intake and stroke. These results suggest that seafood consumption may influence stroke risk; however, identification of mechanisms or alternate explanations for the results requires further study. The type of seafood meal, particularly the method of preparation, is not recorded in most observational studies but may be a major effect modifier." (IOM seafood report, page 98)

Evidence Related to Lipid Profile
The following table summarizes the number of studies the IOM committee reviewed in adults on lipid profile and seafood or omega-3 fatty acid intake. The most common outcome measures were serum triglycerides, total serum cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and lipoprotein lipase.

Lipid Profile-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Randomized controlled	12	11	1
Cohort	1	0	1

Six of 13 primary studies (all randomized controlled trials) reported results related to seafood consumption. The remaining studies assessed omega-3 fatty acid supplements or biomarkers of omega-3 fatty acid consumption. Eleven of 13 primary studies (all randomized controlled trials) showed evidence for one or more improved lipid indicator with increased omega-3 fatty acid intakes. The evidence tended to be the strongest for decreased serum triglyceride levels with increasing intake of EPA/DHA. Omega-3 fatty acid intake was only weakly associated with levels of other serum lipids. (IOM seafood report, pages 98-99)

Based on its review of the evidence, the IOM committee concluded that, "In the general population, the effect from increased seafood consumption on the lipid profile is unclear. However, experimental studies of EPA/DHA supplementation at levels >1 g per day showed decreased triglyceride levels; the effect on other components of the lipid profile is less clear." (IOM seafood report, page 106)

Evidence Related to Blood Pressure
The following table summarizes the number of studies the IOM committee reviewed in adults on blood pressure and seafood or omega-3 fatty acid intake. The most common outcome measures were systolic and diastolic blood pressure.

Blood Pressure-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Cochrane review	1	0	1
Meta-analysis	1	0	1
Randomized controlled	5	5	0
Cohort	1	0	1
Cross-sectional	1	1	0

Four of the seven primary studies reported results on seafood consumption. The remaining three considered omega-3 fatty acid supplements or biomarkers of omega-3 fatty acid intake. Six of seven primary studies (5 randomized controlled trials and the only cross-sectional study) found evidence for improved blood pressure with supplementation of omega-3 fatty acids in quantities that far exceed the intake that one might achieve through a normal diet.

Based on its review of the evidence, the IOM committee stated that, "It is unclear from these studies whether seafood consumption, in the range consumed by most Americans, is an effective means to reduce blood pressure. Further, it is not known if the association between EPA/DHA consumption and blood pressure is linear of if there is a threshold below which no benefit is detectable." (IOM seafood report, page 101)

Evidence Related to Arrhythmia
The following table summarizes the number of studies the IOM committee reviewed in adults on arrhythmia and seafood or omega-3 fatty acid intake. The most common outcome measures were heart rate variability indexes.

Arrhythmia-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
Review	1	1	0	0
Randomized controlled	2	1	0	1
Cohort	1	0	1	0
Cross-sectional	1	0	0	1

Two of four primary studies (one cohort and one cross-sectional) reported results on seafood consumption; the randomized controlled trials administered omega-3 fatty acid supplements. Although none of the differences was statistically significant, one randomized controlled trial found evidence for omega-3 fatty acid supplements and decreased heart rate variability. One randomized controlled trial and the cross-sectional study found evidence for the opposite effect.

The IOM committee did not include a specific qualitative summary comment on the evidence for arrhythmia. (IOM seafood report, pages 101-102)

Evidence Related to Other Cardiac Benefits
The following table summarizes the number of studies the IOM committee reviewed in adults on other cardiovascular indicators and seafood or omega-3 fatty acid intake. Outcome measures included fibrinogen, clotting factors and platelet aggregation.

Other Cardiac Benefits-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Randomized controlled	2	1	1

Both randomized controlled trials examined seafood and omega-3 fatty acid supplements in combination. One found evidence for improved cardiovascular indicators while the other did not.

The IOM committee did not include a specific qualitative summary comment on the evidence for other cardiac indicators (IOM seafood report, pages102-103).

Evidence Related to Diabetes
The following table summarizes the number of studies the IOM committee reviewed in adults on type 2 diabetes and seafood or omega-3 fatty acid intake. Subjects had type 2 diabetes in two studies, hypertension in one study, hyperlipoproteinemia in one study and combined hyperlipidemia in one study. The most common outcome measures were fasting blood glucose levels and glycosylated haemoglobin.

Diabetes-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Randomized controlled	4	1	3
Trial	1	1	0
Cross-sectional	1	0	1

Three of six primary studies assessed exposure to seafood; the other three studies administered omega-3 fatty acid supplements. One randomized controlled trial considered coagulation and fibrinolytic factors in subjects with type 2 diabetes. This study found significant improvements with a diet (including seafood) and exercise intervention. One of the five remaining primary studies (categorized simply as a "trial") found evidence for improved glycemic control with increased omega-3 fatty acids. The other four studies did not find evidence for a benefit.

Based on its review of the evidence, the IOM committee stated that, "Although EPA/DHA consumption has been shown to improve lipid profiles and other indicators of cardiovascular risk in those with type II diabetes, there is currently no evidence that intakes of 2-4 g/day of EPA/DHA can improve gylcemic control." (IOM seafood report, page 103)

Evidence Related to Asthma and Allergies
The following table summarizes the number studies reviewed in adults on asthma or allergies and seafood or omega-3 fatty acid intake. The outcomes were asthma or allergic rhinitis.

Asthma and Allergies-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Cohort	1	0	1
Cross-sectional	1	1	0

Two primary studies (one cohort and one cross-sectional) measured exposure to dietary omega-3 fatty acids, including seafood. The cohort study assessed rates of asthma and found no evidence for reduced risk of asthma with increased dietary omega-3 fatty acids. The case-control study assessed dietary omega-3 fatty acid intake in cases with incident asthma and/or allergic rhinitis and found evidence for reduced asthma symptoms.

The IOM committee did not include a specific qualitative summary comment on the evidence for asthma and allergies in adults. (IOM seafood report, page 103)

Evidence Related to Cancer
The following table summarizes the number of studies the IOM committee reviewed in adults on cancer and seafood or omega-3 fatty acid intake. Outcomes included rates of total, pancreatic, breast, prostate, ovarian, colorectal, and lung cancer.

Cancer-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association	Evidence of an adverse effect
Review	3	0	3	0
Randomized controlled	1	0	1	0
Cohort	23	6	14	3
Case-control	1	0	1	0
Case-cohort	1	1	0	0

All 26 primary studies reported results on seafood consumption. The randomized controlled trial showed no association between seafood intake or omega-3 fatty acid supplements and risk of pancreatic cancer. Six of 23 cohort studies found evidence for reduced risk of cancer with increased seafood consumption: two of the six cohort studies found reduced risk of colorectal, colon and/or rectal cancer, two found reduced risk of pancreatic cancer, and two found reduced risk of lung cancer. The case-cohort study showed evidence for an association between seafood consumption and reduced risk of colon cancer in men but not women. Three of 23 studies found evidence for seafood consumption and increased risk of cancer (prostate cancer, two studies; breast cancer, one study). The case-control study found no evidence for an association between seafood or omega-3 fatty acid intake and risk of ovarian cancer.

Based on its review of the evidence, the IOM committee stated that, "The biological functions associated with consumption of omega-3 fatty acids suggest that it may have some impact on cancer risk. Available evidence comes primarily from observational studies rather than randomized controlled trials. A small number of these studies show some protection for certain types of cancer (i.e., breast, colorectal, and lung), whereas others support an increase in risk (e.g., breast). The majority of the studies, however, conclude there is no significant effect on risk for cancer associated with seafood consumption or intake of other sources of EPA/DHA. Overall, the consumption of seafood, ALA, or EPA/DHA from all sources does not appear to decrease cancer risk." (IOM seafood report, page 104)

Evidence Related to Age-Related and Other Neurological Outcomes
The following table summarizes the number of studies the IOM committee reviewed in adults on age-related and other neurological outcomes and seafood or omega-3 fatty acid intake. Outcomes included measures (such as incidence) of Alzheimer's disease, Parkinson's disease, multiple sclerosis, cerebral palsy and cognitive function.

Age-Related and Other Neurological Outcomes-Studies Reviewed by the IOM Committee

Study Type	Number of Studies
	Total	Evidence of a benefit	Evidence of no association or no clear association
Cohort	5	2	3
Nested cohort	1	1	0
Case-control	2	1	1

Five of eight primary studies (two cohort, the nested cohort, and two case-control) reported results on seafood consumption. The remaining studies assessed dietary sources of omega-3 fatty acids in general. Four of eight primary studies found evidence for improved age-related and other neurological outcomes. All three (cohort) studies that assessed incidence of Alzheimer's disease and seafood consumption found evidence of a reduced risk of developing the disease. The other one of the four positive studies was a case-control study that assessed seafood consumption and incidence of multiple sclerosis; a reduced risk was seen in women but not men. The other cohort that focused on multiple sclerosis found no evidence for reduced risk.

Based on its review of the evidence, the IOM committee stated that, "Consumption of EPA/DHA, specifically from seafood consumption, may provide some protection in terms of age-related cognitive decline as well as risk for Alzheimer's and other neurological diseases. It should be noted that... evidence for reduced risk for these diseases comes primarily from observational studies. The beneficial effects appear to be more closely related to the consumption of seafood and/or global intake of DHA rather than EPA or ALA. Overall, the evidence is tenuous and counterbalanced by a number of studies that did not find significant benefits." (IOM seafood report, page 104)

To learn more:

• 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

International Context - Recommendations of Authoritative Health Groups

The recommendations of authoritative groups around the world are consistent with the recommendations in Canada's Food Guide to eat at least two Food Guide Servings (at least 150 grams) of fish each week, emphasizing types that are higher in the long-chain omega-3 fats. There is increasing acceptance of evidence that, in populations with only modest intakes of EPA and DHA, increased dietary consumption could further improve health status.

Overview
More Detailed Summary

International Context-Recommendations of Authoritative Health Groups
-Overview

The following chart provides a summary of the recommendations about consumption of seafood and long-chain omega-3 fatty acids made by international authoritative health groups. It is interesting to note that even when they take account of the same evidence, the expert interpretations and consequent recommendations can vary. Nevertheless, all are fairly consistent with the recommendations in Canada's Food Guide to eat at least two Food Guide Servings (at least 150 grams) of fish each week, emphasizing types that are higher in the long-chain omega-3 fats.

A more detailed summary is also available.

Recommendations for Fish Consumption from Authoritative Health Groups

Authoritative Group	Year	Target Group	Health Benefit Rationale	Recommendation
Health Canada (Canada's Food Guide)	2007	General population	Reduced risk of CVD	At least two 75-g portions [at least 150 g] of fish each week, emphasizing fatty fish
International Scientific Advisory or Regulatory Agencies
Institute of Medicine expert committee	2007	(1) Females who are or may become pregnant or who are breastfeeding	Increased duration of gestation; improved developmental outcomes in infants and children	Two 3-ounce (cooked) servings [~170 g] per week, especially types with higher concentrations of EPA and DHA; up to 12 ounces per week
		(2) Children up to age 12	Improved developmental outcomes
		(3) Adolescent males, adult males, and females who will not become pregnant	Decreased risk of cardiovascular deaths and cardiovascular events	Two 3-ounce (cooked) servings [~170 g] per week There may be additional benefits from including high EPA/DHA selections
		(4) Adult males and females at risk for cardiovascular disease	The guidance for people with a risk for CVD and those with a history of CVD is not materially different
World Health Organization and Food and Agriculture Organization, United Nations	2003	General population	Protective against coronary heart disease and ischemic stroke	Regular fish consumption (1-2 servings per week, each providing an equivalent of 200-500 mg of EPA and DHA)
U.S. Dietary Guidelines Advisory Committee	2005	General population	Reduced risk of sudden death and coronary heart disease death in adults	Two servings (approximately 8 ounces [or ~225 g]) per week of fish high in EPA and DHA
United Kingdom Scientific Advisory Committee on Nutrition	2004	General population (including pregnant women)	Reduced risk of CVD; beneficial effects on fetal development	At least two portions of fish per week, of which one should be oily
European Food Safety Authority	2005	General population	Benefits to the cardiovascular system and potential benefits to fetal development	One to two portions (of about 130 g per portion) of fatty fish per week
Health Council of the Netherlands	2007	General population	Reduced risk of CVD, reduced risk of death from cardiovascular diseases	450 mg/day of omega-3 fatty acids from fish, which equates to 2 portions of fish per week (100-150 g per portion), at least one portion being oily fish
Other Health Organizations or Professional Associations
American Heart Association	2006	General population	CVD risk reduction	Eat fish, preferably oily fish, at least twice a week
National Heart Foundation of Australia	1999	General population as well as high-risk individuals	Protection against coronary heart disease	At least two fish (preferably oily fish) meals per week
European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice (joint task force)	2007	General population	Reduced risk of CVD	Encourage fish, especially oily fish
American Dietetic Association and Dietitians of Canada	2007	General population (including pregnant women)	Reduced risk of CVD, sudden cardiac death, cardiovascular events, and possibly stroke Insufficient evidence for recommendations that differ for mental health or visual problems Neural and visual maturation in the fetus	Two servings (8 ounces [or ~225 g]) of cooked fish, preferably fatty fish, per week, providing about 500 mg/day of EPA and DHA

CVD = cardiovascular disease; DHA = docosahexaenoic acid; DPA = docosapentaenoic acid; EPA = eicosapentaenoic acid; PUFA = polyunsaturated fatty acids

International Context-Recommendations of Authoritative Health Groups
-More Detailed Summary

International Scientific Advisory or Regulatory Agencies
Other Health Organizations or Professional Associations

International Scientific Advisory or Regulatory Authorities

• In its comprehensive review of the benefits and risks of eating seafood, an independent expert committee commissioned by the Institute of Medicine of the U.S.-based National Academy of Sciences, Food and Nutrition Board (released in October 2006; published in 2007) indicates that "For most of the general population, balancing benefits and risks associated with seafood consumption to obtain nutritional and health benefits can be achieved by selecting seafood from available options in quantities that fall within accepted dietary guidelines." (page 15)
  
  Specifically with respect to heart disease, the committee concluded that "observational evidence suggests that increased seafood association is associated with a decreased risk of cardiovascular deaths and cardiovascular events in the general population." (pages 5, 106) The "evidence is inconsistent for protection against further cardiovascular events in individuals with a history of myocardial infarction from consumption of EPA/DHA-containing seafood or fish-oil supplements" (pages 5, 106); the committee concluded that the guidance for this population should not differ from that for the general population (page 208). With respect to benefits from maternal intake, the evidence suggests an association between increased duration of gestation and improved developmental outcomes in infants of mothers who consume seafood or fish-oil supplements. (pages 5, 89-90) More details on these findings are available.
  
  The committee identified four population groups for which the evidence supports consumption guidance for seafood:
  
  - The report concluded that adolescent males, adult males, and females who will not become pregnant may reduce their risk for cardiovascular disease by consuming seafood regularly, such as two 3-oz servings per week [~170 grams per week]. The evidence suggested that the guidance for people with a risk for cardiovascular disease (CVD) and those with a history of CVD is not materially different from that recommendation, (page 208) and that "there may be additional benefit from including seafood comparatively high in EPA and DHA." (page 212)
  - The report acknowledged that females who are pregnant, who may become pregnant or who are breastfeeding, and children up to age 12, may benefit from consuming two 3-oz servings of seafood, especially those with higher concentrations of EPA and DHA. (pages 207, 212)
  
• The World Health Organization and Food and Agriculture Organization (WHO/FAO) (2003) indicate that "Regular fish consumption (1-2 servings per week) is protective against coronary heart disease and ischaemic stroke and is recommended. The serving should provide an equivalent of 200-500 mg of eicosapentaenoic and docosahexaenoic acid. People who are vegetarians are recommended to ensure adequate intake of plant sources of α-linolenic acid." (page 90)
• The Dietary Guidelines for Americans (2005) concludes that "The consumption of two servings (approximately 8 ounces [~225 grams]) per week of fish high in EPA and DHA is associated with reduced risk of both sudden death and CHD [coronary heart disease] death in adults. To benefit from the potential cardioprotective effects of EPA and DHA, the weekly consumption of two servings of fish, particularly fish rich in EPA and DHA, is suggested." (page 22)
• The United Kingdom's Scientific Advisory Committee on Nutrition (SACN) (2005) weighed the nutritional benefits associated with consumption of seafood against possible risks. The committee "endorsed the population recommendation to eat at least two portions of fish per week, of which one should be oily, and agreed that this recommendation should also apply to pregnant women." (page 3)
  
  SACN further indicated that "An increase in population oily fish consumption to one portion a week, from the current levels of about a third of a portion a week, would confer significant public health benefits in terms of reduced risk of cardiovascular disease. There is also evidence that increased fish consumption might have beneficial effects on fetal development." (page 3)
  
  SACN also emphasized that "this recommendation represents a minimal and achievable average population goal and does not correspond to the level of fish consumption required for maximum nutritional benefit." (page 3)
  
• The European Food Safety Authority (2005) was requested by Parliament to conduct a scientific assessment of the health risks related to human consumption of wild and farmed fish. The Interpanel working group set up to conduct this assessment concluded that: "There is evidence that fish consumption, especially fatty fish, benefits the cardiovascular system and may also benefit foetal development. One to two portions (of about 130 g per portion) of fatty fish per week are sufficient to reach the daily intake for LC [long-chain] n-3 PUFA recommended for potential benefits to health." (page 72)

• The Health Council of the Netherlands Guidelines for a healthy diet (2006) recommend that to reduce the risk of cardiovascular disease, the average person should increase their intake of fish to two portions per week (each 100-150 g), at least one of which should be oily. This amount corresponds to 450 mg of omega-3 fatty acids per day. (pages 15, 17, 50, 73) The Council further states that "There is good reason to believe that the association between fish consumption and the risk of mortality from cardiovascular diseases is not linear. The greatest protective effect is achieved by switching from non-consumption or very occasional consumption of fish to the consumption of at least one portion of fish a week." (page 73)

Other Health Organizations or Professional Associations

• The American Heart Association (2006) recommends that individuals "consume a variety of fruits, vegetables, and grain products, especially whole grains; choose fat-free and low-fat dairy products, legumes, poultry, and lean meats; and eat fish, preferably oily fish, at least twice a week." (page 83)
• The National Heart Foundation of Australia's National Nutrition and Metabolism Advisory Committee (1999) recommends that "at least two fish (preferably oily fish) meals per week are consumed; both plant and marine n-3 polyunsaturated fatty acids are consumed since it is possible that α-linolenic acid and marine n-3 polyunsaturated fatty acids protect against CHD by different mechanisms..." (page 2, position statement reprint)
• The European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice (Fourth Joint Task Force, 2007) recommend that to manage total cardiovascular disease risk, all individuals should be advised about food choices that are associated with lower CVD risk. Fish (especially oily) should be encouraged. (page E17) Among the extensive evidence they considered are "prospective epidemiologic population studies [showing] lower rates of fatal coronary occurrences and sudden death among people who regularly consume fish than among nonconsumers." (page S27)
• The American Dietetic Association (ADA) and Dietitians of Canada (DC) (2007) recommend that the diet should "emphasize a reduction in saturated fatty acids and trans fatty acids and an increase in n-3 polyunsaturated fatty acids". ADA and DC "recommend a food-based approach for achieving these fatty acid recommendations", through an eating pattern that:
  - is high in vegetables and fruit, whole grains, legumes, nuts and seeds,
  - includes lean protein such as lean meats, poultry, and low-fat dairy products,
  - includes fish, especially fatty fish high in omega-3 fatty acids, and - uses non-hydrogenated margarines and oils. (page 1599)
  
  ADA and DC "consider that n-3 PUFA from fish are an important part of a healthful diet, and recommend two servings per week, preferably fatty fish. Approximately 8 oz [~225 g] of cooked fish per week provides about 500 mg/day EPA and DHA." (page 1602) Their literature review revealed benefits from EPA and DHA consumption that include reduced risk of CVD, sudden cardiac death, cardiovascular events, and possibly stroke, as well as benefits to the fetus and infant (neural and visual maturation) from higher maternal DHA status both before birth and via breastmilk after birth. ADA and DC also concluded that "sufficient information is as yet unavailable to suggest recommendations for dietary n-3 fatty acids with respect to mental health or visual problems that are different from those based on CVD." (page 1605)

To learn more:

On this website

• Evidence behind the Canada's Food Guide recommendation for fish
• Are Canadians meeting the recommendations?

Other resources

International Scientific Advisory or Regulatory Agencies

• 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
• Joint WHO/FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases (2003) 
  www.who.int/dietphysicalactivity/publications/trs916/en/
• (U.S.) 2005 Dietary Guidelines Advisory Committee report (2005) - section on fats 
  www.health.gov/dietaryguidelines/dga2005/report/HTML/D4_Fats.htm or www.health.gov/dietaryguidelines/dga2005/report/PDF/D4_Fats.pdf
• (U.K.) Scientific Advisory Committee on Nutrition/Committee on Toxicology (2005) 
  www.food.gov.uk/multimedia/pdfs/fishreport2004full.pdf
• European Food Safety Authority: Opinion of the Scientific Panel on Contaminants in the Food Chain on a Request From the European Parliament Related to the Safety Assessment of Wild and Farmed Fish. The EFSA Journal 2005; 236:1-118
  www.efsa.europa.eu/EFSA/Scientific_Opinion...
• Health Council of the Netherlands: Guidelines for a Healthy Diet. The Hague: Health Council of the Netherlands, 2006
  -summary: www.gr.nl/samenvatting.php?ID=1481
  -full guidelines: www.gr.nl/pdf.php?ID=1481

Other Health Organizations or Professional Associations

• Lichtenstein AH, Appel LJ, Brands M et al.: Diet and lifestyle recommendations revision 2006: A scientific statement from the American Heart Association nutrition committee. Circulation 2006;114:82-96
  http://circ.ahajournals.org/cgi/reprint/CIRCULATIONAHA.106.176158
• Kris-Etherton PM, Harris WS, Appel LJ for the Nutrition Committee: AHA Scientific Statement: Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation 2002;106:2747-2757
  http://circ.ahajournals.org/cgi/reprint/106/21/2747
• National Heart Foundation of Australia: A review of the relationship between dietary fat and cardiovascular disease. Aust J NutrDiet 1999;56(4 Suppl):S5-S22
  -abstract and ordering information: www.ajnd.org.au/
• National Heart Foundation of Australia: Dietary fats: a position statement from the National Heart Foundation's Nutrition and Metabolism Advisory Committee. Aust J NutrDiet 1999;56(4 Suppl):S3-4
  -reprint available at: www.heartfoundation.org.au/document/NHF/Dietary_Fats_1999.pdf
• Graham I, Atar D, Borch-Johnsen K, Boysen G et al: European guidelines on cardiovascular disease prevention in clinical practice: executive summary. Fourth joint task force of the European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice. Eur J Cardiovasc Prev Rehab 2007; 14(Suppl 2): E1-E40
  www.escardio.org/NR/rdonlyres/2A4EF76B-D3AD-4313-B8BF-7D0BCC405CB8/0/guidelines_CVD_Prev_ES_FT_2007.pdf
• 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/frm_resource/imageserver.asp?id=1024&document_type=document&popup=true&contentid=9301