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Seafood Nutrition

Seafood nutrition has been vital for enhancing human health throughout history. Fish and shellfish, including mollusks and crustaceans, make up a significant portion of the aquatic life consumed as food worldwide.

The oceans and rivers of the world teem with an incredible diversity of fish and shellfish, coming in various shapes, sizes, and colors. This range includes the small, silvery herring found in the vast shoals of the cold Atlantic waters and the vibrant, rainbow-colored parrotfish inhabiting tropical seas.

seafood nutriion facts
Seafood-fish. Photo credit: Seafood academy.

List of seafood along with the illustration of their nutrition facts and health benefits:

alaska pollock
Alaska pollock
anchovies
Anchovies
arctic char
Arctic char
Atlantic cod
Atlantic cod
atlantic-meckerel
Atlantic mackerel
Blue crab
Blue crab
branzino
Branzino (Sea bass)
brook trout
Brook trout
Channel catfish
Channel catfish
Chinook salmon
Chinook salmon
common carp
Common carp
crawfish
Crawfish
dover sole
Dover sole
Haddock fish
Haddock
hake fish
Hake fish
Halibut
Halibut
herring fish
Herrings
american lobster
Lobsters
pacific oyster
Oyster
Red snapper
Red snapper
Atlantic salmon
Salmon
sardines
Sardines
sea scallops
Sea Scallops
shrimp
Shrimp
Skipjack tuna
Skipjack tuna
sockeye salmon
Sockeye salmon
striped bass
Striped bass
atlantic-surf-clam
Atlantic surf clam
tilapia fish
Tilapia
Trout
Trout
walleye fish
Walleye
yellowfin tuna
Yellowfin tuna

Advancements in transportation have expanded the variety of fish and shellfish now accessible to consumers. These aquatic delicacies can be enjoyed raw or prepared through various cooking methods, and they come with the added benefit of being exceptionally nutritious, providing ample protein, vitamins, and minerals. Most of these fish belong to saltwater species, with the remainder being freshwater varieties.

Sea fish

All oceans provide a habitat for a diverse array of fish species. Notably, when it comes to edible fish from the ocean, they can be broadly categorized into two groups: flatfish and roundfish.

Flatfish that reside on or near the seabed are often referred to as "benthic" or "demersal" fish. These fish spend the majority of their time resting on the seabed and exhibit minimal swimming activity. What's intriguing about flatfish is that they are either right-eyed or left-eyed, a unique adaptation for their seafloor habitat. These fish typically have lean, white meat, with the majority of their nutritious oil stored in their livers. Examples of flatfish include brill, dover sole, halibut, dab, plaice, megrim, turbot, and more. A single flatfish can yield four fillets, with two obtained from each side.

Roundfish can be further categorized as pelagic or deepwater fish. They have an oval or round cross-section. Some roundfish, such as freshwater trout, complete their life cycle in rivers and lakes. Pelagic fish, on the other hand, are primarily oily fish that tend to form schools near the coastal shelves of the sea. They are known as oily fish because their nutritious oil is distributed throughout their flesh.

Within the category of round white fish, there are numerous families of fish, including Sea bass, hake, mullet, Pollock, cod, bream, gurnard, and many others.

Round, pelagic oily fish encompass species like anchovies, sardines herrings, tuna, and more.


Migratory fish

Some fish species, such as salmon and trout, exhibit anadromous behavior. This means that as adults, they reside in saltwater but undertake an incredible migration of thousands of miles upstream to freshwater environments in the spring for the purpose of spawning.

These remarkable migratory fish adhere to a specific path, traversing from their original freshwater streams, rivers, lakes, and coastal areas, all the way to the deep ocean waters before ultimately returning to their birthplace to reproduce and subsequently complete their life cycle.


Deep sea and game fish

Beneath the depths of the world's oceans, numerous species of fish inhabit regions seldom visited by the shore. They display peculiar shapes and striking, vibrant hues. The majority of edible deep-sea fish thrive in the coastal waters of New Zealand, South Africa, and South America. Among these are swordfish, sharks, marlins, barracudas, and more.


Freshwater fish

While there exists a diverse array of freshwater fish, they are not typically found in large quantities. Consequently, there has been limited commercial exploitation of these fish, with exceptions like salmon and trout, which are often raised on farms. Notably, Carp, Channel cat, and char are increasingly being cultivated.

The majority of freshwater fish, including pike, grayling, and roach, are primarily caught by anglers. Meanwhile, tilapia production has shifted towards aquaculture. It's worth noting that freshwater fish tend to have a milder and less robust flavor compared to their saltwater counterparts.


Crustaceans

This extensive shellfish family boasts an impressive variety, encompassing crabs, lobsters, crawfish, and prawns and shrimps. They exhibit an astonishing array of shapes and sizes, with their defining characteristic being an external exoskeleton that conceals a delectably tender interior.

While preparing, cooking, and enjoying crustaceans may demand significant effort, the rewards are unquestionably worth it.


Mollusks

This family of selfish is normally divided into two main groups- gastropods, which include whelks and winkles, and bivalves, which have attractive hinged external shells that encase tender, delicate flesh within, such as clams, oysters, and mussels.


Cephalopods

Cephalopods, including Squid, Octopus, and Cuttlefish, belong to this group. They are more closely related to snails than to fish, and their name originates from the Greek term meaning "head with feet."

Their distinctive head is bulbous, housing the mouth equipped with two jaws, resembling a parrot's beak. This head is encircled by tentacles adorned with suckers, which serve the dual purpose of locomotion and capturing prey.

Furthermore, many cephalopods possess an ink sac that releases a dark fluid, primarily meant to deter predators and create a smokescreen during attacks. Interestingly, this fluid, commonly known as ink, can also be used in culinary applications.


Benefits of Seafood for Your Health

  1. Seafood, including fish and crustaceans, is not only delicious but also a nutritious choice. It is low in calories and fat, making it a healthy option.

  2. Crustaceans and mollusk lean white meat are excellent sources of protein, providing all essential amino acids in the right proportions.

  3. Research studies have indicated that incorporating seafood into your diet can reduce the risk of heart attacks, strokes, obesity, and hypertension. Seafood is low in saturated fat and rich in heart-healthy polyunsaturated fats, such as omega-3 fatty acids.

  4. The American Heart Association recommends seafood consumption, with an emphasis on at least two servings of oily fish, to meet your essential fatty acids, protein, mineral, and fat-soluble vitamin needs.

  5. Seafood, particularly oily fish, is a abundant source of vitamin A and long-chain omega-3 fatty acids, including eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), which are essential for maintaining healthy skin and mucous membranes.

  6. Furthermore, research suggests that these fatty acids, particularly DHA, play a crucial role in neural system development, especially in infants and children.

  7. In adults, multiple large trials have examined the impact of fish or fish oils on heart disease. In the "GISSI Prevention Trial, individuals who took a daily 1-gram capsule of omega-3 fats for three years after a heart attack were less likely to experience a repeat heart attack, stroke, or sudden death compared to those who received a placebo".

  8. Freshwater crustaceans like crawfish feed on small insects and zooplankton, providing an excellent source of B-complex vitamins. Shellfish meat is also rich in folates, niacin, vitamin B6, thiamin, and riboflavin.

  9. Invertebrates, such as crawfish, are low on the food chain and accumulate minimal amounts of heavy metals like mercury. The Food and Drug Administration (FDA) recommends that pregnant women consume at least 8 to 12 ounces of low-mercury seafood per week.

  10. Seafood is packed with essential minerals, including iron, selenium, iodine, calcium, zinc, potassium, phosphorus, and magnesium. It is also a valuable dietary source of iodine.

  11. According to Cornell University and the New York Sea Grant Extension Program. 2012, these fatty acids can help lower blood pressure, heart rate, and improve cardiovascular function. They have been shown to reduce the risk of arrhythmias (abnormal heartbeats) and slow the growth of atherosclerotic plaque.

  12. Seafood is a rich source of essential vitamins, including niacin, vitamin B6, vitamin E, vitamin B12, thiamin, and riboflavin. Oily fish like trout also provide generous amounts of vitamins A and D, with vitamin D playing a crucial role in calcium metabolism metabolism and cancer protection.


Buying and storage

Whole fresh fish and shellfish

The US-FDA on its guidelines for Selecting and Serving Fresh and Frozen Seafood Safely, illustrates following points for buyers:

  • The fish should smell fresh and not fishy, or ammonia-like.

  • The gills should be red, moist and bright.

  • The eyes should be full, Shiny, and flush with the head.

  • The skin should be glistening, pearly, tight, and adhere to the flesh.

  • The flesh should be firm and elastic; it should not be marked, retain finger Impressions, or separate easily from the bones.

  • The scales should cling to the skin, and be Shiny and intact.

  • The belly should be neither swollen nor dull and should have a sweet and pleasant odor (strong fish smell indicates lack of freshness).

  • A muddy smell can impregnate various fish, depending on where they live but it does not mean that the fish is not fresh.

  • Shrimp, scallops, and lobster flesh should be clear with a pearl-like color and little or no odor.

  • Fresh fish portion
    • Fillets (pieces of flesh cut from this spine)

    • Steaks (thick cross cuts or pieces)

    The flesh should be firm elastic and shiny; it should cling well to the bones and have a pleasant smell. It should not the brown Yellow or dried out.

Frozen fish
  • The flesh should have a fresh, firm, and glistening appearance without evidence of drying or freezer burn.

  • It should also be solidly frozen and enclosed in intact watertight packaging without Frost and ice crystals on the inside.

A defrosted fish will have a slightly different flavor and texture from a fresh fish. It should be eaten as soon as possible and should not be refrozen without being cooked beforehand.

Salt-cured fish

The flesh should have a good color and pleasant smell, not be dried out.

Pickled fish

Pickling has always been a good way to preserve fish. Curing in vinegar or brine is an effective way of pickling fish. It is particularly well suited to oily fish such as herrings.

Canned fish

Canned fish is a useful store-cupboard utility and is perfect for salads, snacks, sandwiches, and other quick meals. Anchovies, sardines, salmon, and tuna can make the best canned fish.

Smoked fish

There are two methods- cold and hot smoking which give very different results. For both methods, the fish must first be dry salted or soaked in brine. The fish then smoked over different types of wood, all of which impart their own, unique, distinctive taste. Other flavorings such as Jasmine tea may also be used.

Cold-smoked fish-To produce a good quality cold-smoked Fish requires a high degree of skill because it is difficult to get the flavor and texture just right. The cold smoking process is done at a temperature of about 30 to 35 degrees Celsius which cures but does not cook the fish. Some cold-smoked fish such as salmon, halibut, and trout are eaten RAW others such as kippers and haddocks are usually cooked.

Hot smoked fish-Fish that are cured or hot smoked at a temperature of 80 to 85°C which both cook and use- need no further cooking. Trout, Mackerel, eel, and herrings can all be smoked.

Arbroath smokie-These hot-smoked haddocks have deep golden sin and soft pale gold flesh with a more delicate flavor than cold-smoked haddocks. In their native Scotland, they are a favorite breakfast or supper dish.

Here are some storing tips:

Once at home, place fish/shellfish in the refrigerator or freezer soon after buying it. If you intend to use seafood within 2 days after purchase, store it in a clean refrigerator at a temperature of 40°F or below. Otherwise, wrap it tightly in plastic, foil, or moisture-proof paper and store it in the freezer.


Preparation

The US -FDA issues the following guidelines:

Thaw frozen seafood gradually by placing it in the refrigerator overnight. If you have to thaw seafood quickly, either seal it in a plastic bag and immerse it in cold water, or — if the food will be cooked immediately thereafter — microwave it on the “defrost” setting and stop the defrost cycle while the fish is still icy but pliable.

For cooking-most seafood should be cooked to an internal temperature of 145°F. If you don’t have a food thermometer, there are other ways to determine whether seafood is done.

Fish: The flesh is clear and separates easily with a fork

Shrimp, Scallops, Crab, and Lobster: The flesh becomes firm and clear

Clams, Mussels, and Oysters: The shells open during cooking — throw out ones that don’t open

Uncooked spoiled seafood can have sour, rancid, fishy, or ammonia odors. These odors become stronger after cooking. If you smell sour, rancid, or fishy odors in raw or cooked seafood, do not eat it. If you smell either a fleeting or persistent ammonia odor in cooked seafood, do not eat it.


Serving ideas:

Follow these serving guidelines on seafood nutrition:

  • It is always best to cook seafood thoroughly to minimize the risk of foodborne illness.

  • Never leave seafood or other perishable food out of the refrigerator for more than 2 hours or for more than 1 hour when temperatures are above 90°F. Bacteria that can cause illness grow quickly at warm temperatures (between 40°F and 140°F).

  • Pregnant women, children older adults, and people with weak immunity should avoid:

    1. Raw or undercooked fish or shellfish/Raw oysters

    2. seafood especially food containing raw or undercooked (for example, sashimi) found in some sushi or ceviche.


Seafood nutrition-Safety profile

As much as possible, avoid eating fish that live in polluted waters, as the flesh of some fish easily absorbs very toxic substances, such as DDT, PCB, and mercury.

Ciguatera toxin poisoning sometimes occurs after consuming fish like grouper, barracuda, sea bass, red snapper or moray eel whose flesh was contaminated by certain large reef fish. Ciguatera toxin does not get destroyed by cooking. Symptoms may include itchiness, diarrhea, vomiting, numbness, sensitivity to hot and cold, dizziness, and muscle weakness. Only symptomatic treatment is possible.

Scombroid (histamine) poisoning commonly results from eating spoiled fish (Bacterial contamination of fresh or canned), including tuna, mahi-mahi, mackerel, skipjack, marlin, etc. Refrigerating or freezing right after it is caught may prevent this condition. Cooking or heating fish cannot prevent it once fish is spoiled. Symptoms may include flushed skin, itchiness, headache, breathing difficulty, blurred vision, abdominal cramps, and diarrhea.

Seafood also harbors bacteria like Vibrio cholerae and E.coli, which are an important cause of bacterial seafood poisoning. Roundworm infection due to anisakiasis is acquired by eating raw fish, especially cod, herring, mackerel, and salmon.

Fish tapeworm infection is acquired by eating raw salmon, herring, and gefilte fish- most infected persons are symptom-free, but symptoms may include vomiting, diarrhea, and abdominal discomfort.

Shellfish Poisoning

Inadvertent consumption of shellfish such as mussels, oysters, scallops, or clams that have fed on toxic algae can cause poisoning.

The poisoning can affect neurological, musculoskeletal, or gastrointestinal systems. Persons experiencing symptoms such as tingling, numbness, weakness, or respiratory distress should be transported rapidly to a hospital.

(Medical disclaimer).


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Further Resources:

  1. Selecting and Serving Fresh and Frozen Seafood Safely.

  2. Seafood nutrition-guide. (opens in new window).

  3. Omega-3 Fatty Acids: An Essential Contribution.

  4. Mercury Levels in Commercial Fish and Shellfish.

  5. pregnancy-and-fish.