Foods like salmon, lobster, and shrimp, are often categorized as “seafood.” But how might you classify these foods when including a freshwater fish, such as trout? Consider the term aquatic foods (also called blue foods), which include any animals, plants, and microorganisms that originate in bodies of water. Examples are:
- Finfish—small pelagic fish (herring, sardines, anchovies), medium pelagic fish (bonito, mahi-mahi), large pelagic fish (tuna, swordfish), salmonids (salmon, trout), carps, cichlids (tilapia), cods (cod, haddock, pollock), and demersal fish (flounder)
- Crustaceans—crabs, shrimp, krill, prawns, lobster
- Cephalopods—octopus, squid
- Mollusks—clams, cockles, sea snails, mussels, scallops
- Aquatic plants—water spinach (Ipomoea aquatica)
- Other aquatic animals—mammals, insects, sea cucumbers
Aquatic foods can be farmed or wild-caught, and are sourced from inland waters like lakes, rivers, and wetlands; coastal areas like estuaries, mangroves, or near-shore; and marine or ocean waters. Despite currently being an important contribution to healthy diets for billions of people globally, aquatic foods are often undervalued nutritionally because their diversity tends to be restricted to protein or energy value, or framed as a monolithic category of “seafood or fish.”  However, there is broad diversity of aquatic foods produced throughout the world and available during every season. Currently, wild fisheries harvest over 2,370 species and aquaculture growers farm approximately 624 species. 
Because aquatic foods are so nutrient rich, food technologists have innovated methods to create processed fish products, including fish powders for infants, fish wafers as a snack, and fish chutneys. 
This page will focus primarily on animal sources of aquatic foods rather than plant sources.
- Omega-3 (DHA/EPA) polyunsaturated fatty acids
- Vitamin A
- Vitamins B6, B12
- Vitamin D
How do aquatic animals stack up against land-based animals, nutritionally?
Aquatic Foods and Health
Certain aquatic animal foods are a major dietary source of two polyunsaturated omega-3 fatty acids (PUFAs)—docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These fatty acids are initially produced by certain types of algae, which are then eaten by aquatic animals so that the fats accumulate in their tissues or organs. Omega-3s are found in all aquatic foods, but particularly in the fatty tissue of oily fish like salmon and mackerel, the liver of lean white fish like cod and halibut, and the blubber or thick layer of fat under the skin of marine animals like seals and whales. Smaller amounts are also found in crustaceans, bivalves, and cephalopods.  Supplements of fish oil, algal oil, and krill oil also contain DHA and/or EPA. Much of the research on aquatic foods and human health focuses on these omega-3s.
Seafood intake is associated with reduced inflammation and blood pressure, and is protective from stroke and other cardiovascular diseases (CVD). Eating just 1-2 servings of fish weekly reduces the risk of death from heart disease by 36%.  This is not solely due to the omega-3 fatty acids, EPA and DHA, but to other components in seafood, such as vitamins B6 and B12 that maintain normal levels of homocysteine.  Omega-3s are also well-researched in their ability to prevent arrhythmias, in which the heart beats abnormally and erratically. Many, but not all, epidemiologic studies show an association with high fish intake and lower risk of heart failure and deaths from heart disease. The earliest epidemiologic research found a low incidence of CVD in the Inuit people in Greenland, attributed to their traditional high-fat diet consisting largely of seal, fish, and other marine animals. Other studies of coastal populations in Japan and Alaska also showed an inverse relationship of higher dietary omega-3s and lower rates of heart disease. 
Research showing a heart benefit with omega-3 supplements is less convincing, though sometimes very high doses of fish oil supplements are prescribed by a physician for the treatment of high triglycerides or thromboses (blood clots). The American Heart Association recommends including 1-2 seafood servings a week in the diet; supplements of 1,000 mg daily containing DHA/EPA are recommended only for people with existing heart disease, based on a potential benefit of lowering triglycerides and risk of arrhythmias and atherosclerosis. [5,6] They do not recommend omega-3 supplements for people without CVD or risk factors for CVD.
Epidemiological studies show that lower intakes of omega-3s are associated with an increased risk of cognitive decline and dementia. Fatty membranes of the brain are rich in DHA, which is associated with optimal functioning of the brain. Some studies show 30-50% lower DHA levels in the hippocampus region (the brain’s “memory bank”) in patients with Alzheimer’s disease.  Lower DHA levels are associated with amyloidosis, a buildup of protein deposits called amyloids, which is believed to progress Alzheimer’s disease.  Both DHA and EPA can also help regulate inflammation and elevated triglycerides, which are associated with an increased risk of cognitive decline and dementia. 
Most epidemiological studies show that fish intakes of greater than one serving per week are associated with a lower rate of cognitive decline and Alzheimer’s disease pathology, particularly in adults ages 65 and older. [10,8] Higher fish intakes have also been associated with a larger volume of gray matter in the brain and a slower decline in memory scores (dementia is linked with decreased gray matter).  However, evidence is lacking to support the use of omega-3 supplements for the prevention or treatment of cognitive decline in later ages. 
Dietary omega-3s play a role in brain development and growth of the fetus during pregnancy and into infancy. DHA is also found in high amounts in the retina, which develops rapidly in the fetus during the last trimester. Cohort studies show that a higher intake of seafood containing DHA (about 8 ounces weekly) is associated with healthier infants. Research following a cohort of mothers and infants found that higher fish consumption during pregnancy (2+ servings fish weekly) compared with no fish intake was associated with higher cognitive scores in infants and young children 3-5 years old, though higher mercury intake was linked with lower scores. [12-13] However these effects lessened in older children; the researchers found in the same cohort that there was no benefit or harm on cognition in children 6-10 years old from an average maternal fish intake of about 1.5 servings weekly or mercury exposure during pregnancy.  Another review found that the benefits of eating moderate amounts of seafood during pregnancy outweighed potential risks from methylmercury exposure.  The 2020 Dietary Guidelines for Americans recommends that pregnant woman consume 8 ounces of low-mercury seafood per week, and children about 3 ounces of low-mercury seafood per week .
Research has also found that swapping red and processed meat with fish and seafood can lower the risk of diseases and premature death. One reason may be differences in types of fat: mostly saturated fat in red meat versus unsaturated fat in seafood. Data from six U.S. cohort studies found that higher intakes of red meat and processed meat were associated with an increased risk of cardiovascular disease and early death, whereas fish was not.  Research from a large Danish cohort study found that replacing red and/or processed red meat with fish or poultry lowered the risk of type 2 diabetes and early death. [18-19]
Consider swapping out red meat in some recipes for seafood:
- Marinate and bake fish instead of grilling burgers and ribs
- Try canned tuna or salmon instead of cold cuts in a sandwich
- Incorporate steamed mussels or canned mackerel or sardines into meals
- Bake/sauté white fish instead of frying a steak
- Roast or grill salmon instead of beef, lamb, or ham
Should I be concerned about contaminants in aquatic foods?
Certain species can carry small amounts of neurotoxic compounds like methylmercury, dioxins, and polychlorinated biphenyls (PCBs). It is believed that these chemicals can delay brain development in infants and modestly increase the risk of cardiovascular disease.  Those most at-risk for these exposures are pregnant and nursing women, breast-fed infants, and young children.
As concerning as this sounds, it is important to weigh the risk versus benefit. A report from the FAO and WHO Expert Committee outlining the risks and benefits of fish consumption found that the benefits of dietary omega-3s outweighed the risks of mercury exposure in childbearing women. Eating fish during pregnancy lowered the risk of delayed fetal brain development compared with pregnant women who did not eat fish. [20,5] Studies have found dioxins and PCB levels in fish to be typically very low, and small exposures to these compounds in pregnant woman will not harm the fetus. Consider that more than 90% of the PCBs and dioxins in the U.S. food supply come not from aquatic foods but from land-based meats, dairy, eggs, and vegetables. There is also limited evidence from epidemiological studies showing an association with higher mercury intake (obtained mostly from aquatic foods) and increased cardiovascular disease. The small exposures to mercury may be offset by the several heart-protective nutrients found in fish and other aquatic species.
Those who eat aquatic foods very frequently (5 or more servings a week) and vulnerable populations (pregnant/nursing women, infants, and toddlers) may limit intake of species highest in mercury (swordfish, shark, bluefin tuna, yellowfin or ahi tuna, canned white albacore tuna, king mackerel, marlin, golden bass). Good choices are cod, catfish, shellfish, oysters, mussels, shrimp, sardines, and scallops; see the Food and Drug Administration guide for other low-mercury seafood. Also check local advisories on levels of contaminants in freshwater fish from lakes and reservoirs, as these types tend to be higher in mercury and PCBs. If no specific guidelines are available, consume up to 6 ounces a week of fish from local waters but limit eating any other aquatic foods during that week.
To minimize risk of harmful pathogens and parasites, cook and store aquatic foods to proper temperatures. See the Food and Drug Administration guidelines on selecting, storing, and serving seafood safely. Another potential risk are harmful alga blooms, or red tides, that can create toxic substances in seafood leading to symptoms like diarrhea, shortness of breath, asthma attacks, and skin rashes. The best way to avoid these toxins is to purchase seafood from reputable suppliers that have high standards for quality and safety.
The impact of aquatic foods on health in developing countries
For Your Health and The Planet’s Health
Modern production of aquatic foods can be split into two different sectors: wild capture and aquaculture. Wild capture production involves harvested wild fish and other aquatic species from the ocean and freshwater sources. Aquaculture is the practice of farming aquatic plants and animals.
In general, the production of any animal-based food tends to have higher greenhouse gas emissions than the production of plant-based foods, with red meat (especially beef and lamb) standing out for its disproportionate impact. However, the production of aquatic foods (through both wild capture and aquaculture) not only produces fewer greenhouse gas emissions and uses less land than red meat production, but many aquatic animal foods also have less environmental impact than poultry production.  That said, beyond emissions and land use, it is important to consider where and how aquatic foods are produced, since environmental as well as social and economic impacts can vary widely in both wild capture and aquaculture sectors. 
The percentage of wild marine fisheries classified as “overfished” has steadily increased over the past few decades. According to an assessment by the Food and Agriculture Organization of the United Nations, the fraction of fish stocks that are within “biologically sustainable” levels decreased from 90% in 1974 to just under 66% in 2017.  Beyond the challenges that overfishing presents for food security and human health, commercial fishing at current scales can also contribute to:
- Habitat destruction from trawling, a fishing method that indiscriminately captures sea creatures with a dragging net on the ocean floor
- Bycatch and discards – marine species caught unintentionally while targeting other species and sizes of fish
- Illegal, unreported and unregulated fishing
- Issues around unfair distribution of trade benefits and food access
Aquaculture is emerging to fill gaps in seafood supply from reductions in existing wild fish stocks. Today, aquaculture represents the world’s fastest growing food production industry, based largely in Asia (China, India, Vietnam, Bangladesh), Europe (Norway), and increasingly in Africa (Egypt). Despite its promise, aquaculture must be done responsibly. For example, insufficiently regulated aquaculture can result in both environmental stressors—such as freshwater use and nitrogen and phosphorus emissions—as well as negative interactions with wild fishery populations through the spread of disease, overuse of antibiotics, escaped species. 
In summary, sustainably and equitably achieving the human health benefits of increased aquaculture production will require policies and technologies that minimize impacts on surrounding ecosystems, industries, and communities. 
Examining the future of aquatic food systems
Aquatic foods are a diverse category of nutrient-dense, protein-rich foods that can also be a healthful animal-based alternative when looking to cut down on red meat or other land-sourced animal foods. Misconceptions exist, such as having a strong off-putting odor (fresh fish should not smell!) or higher cost than other animal protein foods, which may deter people from choosing aquatic foods. However, many aquatic foods are a major source of omega-3 fatty acids and various nutrients that are helpful in the prevention and treatment of cardiovascular disease, and that are vital for normal fetal development. They can also be delicious and satisfying, and incorporated into many meals like salads, stews, sandwiches, and main courses. Here are some recipes and ideas for cooking with aquatic foods.
- Golden CD, et al. Aquatic foods to nourish nations. Nature. 2021.
- FAO. 2020. The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome.
- Shahidi F, Ambigaipalan P. Omega-3 polyunsaturated fatty acids and their health benefits. Annual review of food science and technology. 2018 Mar 25;9:345-81.
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- Siscovick DS, Barringer TA, Fretts AM, Wu JH, Lichtenstein AH, Costello RB, Kris-Etherton PM, Jacobson TA, Engler MB, Alger HM, Appel LJ. Omega-3 polyunsaturated fatty acid (fish oil) supplementation and the prevention of clinical cardiovascular disease: a science advisory from the American Heart Association. Circulation. 2017 Apr 11;135(15):e867-84.
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