Seafood Nutrition
Seafood nutrition plays an indispensable role in enriching human health since the ancient past. Fish and shellfish (mollusks and crustaceans) constitute a major portion of sea life used as food worldwide.
The world's oceans and rivers are filled with fish and shellfish in a huge variety of shapes, sizes, and colors, ranging from the small silver herring that roam in vast shoals in cold Atlantic waters to the rainbow color parrotfish of tropical seas.
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| Seafood-fish. Photo credit: Seafood academy. |
List of seafood along with the illustration of their nutrition facts and health benefits:
With improved methods of transport, there is an increasingly wide range of fish and shellfish available. They can be consumed either raw or cooked in any number of ways and have the added bonus of being incredibly nutritious, offering a good supply of protein, vitamins, and minerals. The majority of fish or saltwater species the rest are freshwater species.
Sea fish
All oceans provide habitat for thousands of species of fish. Ocean edible fish mainly are- flat fish and round fish.
Flat fish live on or near the seabed are known as benthic (demersal) fish. They spend most of the time lying on the seabed and do very little swimming. Flatfish are either right-or left-eyed because of their organ modification adaptation to sea bed habitat. These fish characteristically carry lean, white meat since their nutritious oil is concentrated in the liver. Examples of flatfish are brill, dover sole, halibut, dab, plaice, megrim, turbot, etc. Four fillets can be obtained from a single fish, two from each side.
Round fish can be pelagic or deep water fish. Their body is oval or round on cross section. Round fish like fresh water trout spend their life-cycle in rivers/lakes. Pelagic fish are chiefly oily fish that tend to live in shoals near the coastal shelf of the sea. They are known as oily fish since their nutritious oil is dispersed throughout the flesh.
Round white fish are many different families of fish within this large group; some examples include Sea bass, hake, mullet, Pollock, Cod, Bream, Gurnard, etc.
Round, pelagic oily fish include anchovies, sardines herrings, tuna, etc.
Migratory fish
Certain species of fish like salmon and trout are anadromous in which adults live in saltwater but migrate thousands of miles upstream to fresh water in the spring to spawn.
These large migratory fish follow a specific route to complete their fascinating journey from natal freshwater streams, rivers, lakes, open bay, and to deep ocean waters and back again to its natal waters to spawn and die.
Deep sea and game fish
Deep in the world's oceans live several varieties of fish that rarely come close to the shore. Many have odd shapes and vibrant colors. Most edible deep-sea fish are found around the coasts of New Zealand, South Africa, and South America. Examples are swordfish, shark, marlin, barracuda, etc.
Freshwater fish
There is a wide variety of freshwater fish but not in large quantities. And so, commercially, it has never been worked netting these fish. The exception, of course, is fish like salmon and trout, which are generally farmed. Carp, Channel cat, and char are now increasingly being farmed.
The majority of freshwater fish such as pike, grayling, and roach are caught only by anglers. Most tilapia is now farm-produced. Freshwater fish have a delicate and less robust flavor than seawater fish.
Crustaceans
This family of shellfish is truly enormous. It includes crabs, lobsters, crawfish, prawns and shrimps. They can come virtually in any shape or size, and their distinguishing feature is that their skeleton is on the outside, concealing a soft and delicious flesh inside.
Crustaceans may require considerable efforts to prepare, cook and eat, but they are well 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 house soft, delicate flesh inside, including clams, oysters, and mussels.
Cephalopods
Squid, Octopus, and Cuttlefish come under the heading of cephalopods. They are more closely related to snails than fish. Their name is derived from the Greek meaning ''head with feet''.
The bulbous head consists of the mouth, which has two jaws, like a parrot beak. This is surrounded by tentacles, covered with suckers, which are used for crawling, and seizing the prey.
Most cephalopods also contain any ink sac that emits a blackish fluid designed to repel predators and provide a smokescreen when under attack. This fluid always refers to as ink -can be used for cooking.
Health benefits of Seafood
Seafood nutrition (fish and crustaceans) is a low calorie, low fat, white meat and widely acknowledged as an healthy food.
Crustaceans and mollusk lean white meat is a good source of protein; being complete in all essential amino acids in right proportions.
Research studies suggest that eating seafood can decrease the risk of heart attack, stroke, obesity and hypertension. Seafood is low in saturated fat and higher in “heart healthy” polyunsaturated fat, including omega-3 fatty acids.
American Heart Association recommends consumption of seafood, including consumption of at least 2 servings of oily fish, to fulfil requirements of essential fatty acids, protein, minerals and fat-soluble vitamins.
Seafood, particularly oily-fish are rich source of vitamin-A and long chain omega-3 fatty acids (PUFA). Vitamin-A and omega-3's like eicosapentaenoicacid (EPA), docosapantaenoicacid (DPA) and docosahexaenoic acid (DHA) fatty acids. are essential for healthy mucosa and skin.
Moreover, research studies suggest that these fatty acids, particularly DHA, play an important role in the development of neural system, especially in infants and children.
In adults, several large trials have evaluated the effect of fish or fish oils on heart disease. In the "GISSI Prevention Trial, heart attack survivors who took a 1-gram capsule of omega-3 fats every day for three years were less likely to have a repeat heart attack, stroke, or die of sudden death than those who took a placebo".
Freshwater crustaceans like crawfish preys on small insects and zooplankton which are the finest sources of B-complex vitamins. Shellfish meat is good source of folates, niacin, vitamin B6, thiamin, and riboflavin.
Invertebrates, like crawfish, are at the bottom of the food chain and concentrate very small amounts of heavy metals like mercury. The Food and Drug Administration (FDA) recommend that pregnant women eat at least 8 ounces and up to 12 ounces (340 grams) of a variety of seafood lower in mercury a week.
Seafood nutrition is packed with minerals including iron (10.5% RDI), selenium, iodine, calcium, zinc, potassium, phosphorus (36.5% RDI), and magnesium. It is also a rich dietary source of iodine.
According to Cornell University and the New York Sea Grant Extension Program. 2012- these fatty acids can help lower blood pressure and heart rate and improve cardiovascular function. For example, research has shown that omega-3 fatty acids decrease the risk of arrhythmias (abnormal heartbeats) that can lead to sudden death. Omega-3 fatty acids also decrease triglyceride levels and slow the growth rate of atherosclerotic plaque.
The essential vitamins in seafood includes niacin, vitamin B6, vitamin E, vitamin B12, thiamin, and riboflavin. In addition, being an oily fish like trout have generous amounts of vitamins-A and D.
Vitamin D plays an important role in the calcium metabolism, and offers protection from cancers.
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, scallop, and lobster flesh should be clear with a pearl-like color and little or no odor.
Fillets (pieces of flesh cut from this spine)
Steaks (thick cross cuts or pieces)
Fresh fish portion
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, 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 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 degrees centigrade which both cook and use them 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 woman, children and older adults and people with weak immunity should avoid:
Raw or undercooked fish or shellfish/Raw oysters
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, is 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.
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Further Resources:
Seafood nutrition-guide. (opens in new window).
Omega-3 Fatty Acids: An Essential Contribution.