Nutritional Profile Energy value (calories per serving): Moderate Protein: High Fat: Low to moderate Saturated fat: Low to moderate Cholesterol: Moderate Carbohydrates: Low Fiber: None Sodium: Low (fresh fish) High (some canned or salted fish) Major vitamin contribution: Vitamin A, vitamin D Major mineral contribution: Iodine, selenium, phosphorus, potassium, iron, calcium
About the Nutrients in This Food Like meat, poultry, milk, and eggs, fish are an excellent source of high- quality proteins with sufficient amount of all the essential amino acids. While some fish have as much or more fat per serving than some meats, the fat content of fish is always lower in saturated fat and higher in unsaturated fats. For example, 100 g/3.5 ounce cooked pink salmon (a fatty fish) has 4.4 g total fat, but only 0.7 g saturated fat, 1.2 g monounsaturated fat, and 1.7 g polyunsaturated fat; 100 g/3.5 ounce lean top sirloin has four grams fat but twice as much saturated fat (1.5 g), plus 1.6 g monounsatu- rated fat and only 0.2 g polyunsaturated fat. Omega-3 Fatty Acid Content of Various Fish (Continued) Fish Grams/ounce Rainbow trout 0.30 Lake whitefish 0.25 Source: “Food for t he Heart,” American Health, April 1985. Fish oils are one of the few natural food sources of vitamin D. Salmon also has vita- min A derived from carotenoid pigments in the plants eaten by the fish. The soft bones in some canned salmon and sardines are an excellent source of calcium. CAUTION: do not eat the bones in r aw or cook ed fish. the only bones consider ed edible ar e those in the canned products.
The Most Nutritious Way to Serve This Food Cooked, to kill parasites and potentially pathological microorganisms living in raw fish. Broiled, to liquify fat and eliminate the fat-soluble environmental contaminants found in some freshwater fish. With the soft, mashed, calcium-rich bones (in canned salmon and canned sardines).
Diets That May Restrict or Exclude This Food Low-purine (antigout) diet Low-sodium diet (canned, salted, or smoked fish)
Buying This Food Look for: Fresh-smelling whole fish with shiny skin; reddish pink, moist gills; and clear, bulging eyes. The flesh should spring back when you press it lightly. Choose fish fillets that look moist, not dry. Choose tightly sealed, solidly frozen packages of frozen fish. In 1998, the FDA /National Center for Toxicological Research released for testing an inexpensive indicator called “Fresh Tag.” The indicator, to be packed with seafood, changes color if the product spoils. Avoid: Fresh whole fish whose eyes have sunk into the head (a clear sign of aging); fillets that look dry; and packages of frozen fish that are stained (whatever leaked on the package may have seeped through onto the fish) or are coated with ice crystals (the package may have defrosted and been refrozen).
Storing This Food Remove fish from plastic wrap as soon as you get it home. Plastic keeps out air, encouraging the growth of bacteria that make the fish smell bad. If the fish smells bad when you open the package, throw it out. Refrigerate all fresh and smoked fish immediately. Fish spoils quickly because it has a high proportion of polyunsaturated fatty acids (which pick up oxygen much more easily than saturated or monounsaturated fatty acids). Refrigeration also slows the action of microorgan- isms on the surface of the fish that convert proteins and other substances to mucopolysac- charides, leaving a slimy film on the fish. Keep fish frozen until you are ready to use it. Store canned fish in a cool cabinet or in a refrigerator (but not the freezer). The cooler the temperature, the longer the shelf life.
Preparing This Food Fresh fish. Rub the fish with lemon juice, then rinse it under cold running water. The lemon juice (an acid) will convert the nitrogen compounds that make fish smell “fishy” to compounds that break apart easily and can be rinsed off the fish with cool running water. R insing your hands in lemon juice and water will get rid of the fishy smell after you have been preparing fresh fish. Frozen fish. Defrost plain frozen fish in the refrigerator or under cold running water. Pre- pared frozen fish dishes should not be thawed before you cook them since defrosting will make the sauce or coating soggy. Salted dried fish. Salted dried fish should be soaked to remove the salt. How long you have to soak the fish depends on how much salt was added in processing. A reasonable average for salt cod, mackerel, haddock (finnan haddie), or herring is three to six hours, with two or three changes of water. When you are done, clean all utensils thoroughly with hot soap and hot water. Wash your cutting board, wood or plastic, with hot water, soap, and a bleach-and-water solution. For ultimate safety in preventing the transfer of microorganisms from the raw fish to other foods, keep one cutting board exclusively for raw fish, meats, and poultry, and a second one for everything else. Finally, don’t forget to wash your hands.
What Happens When You Cook This Food Heat changes the structure of proteins. It denatures the protein molecules so that they break apart into smaller fragments or change shape or clump together. These changes force moisture out of the tissues so that the fish turns opaque. The longer you cook fish, the more moisture it will lose. Cooked fish flakes because the connective tissue in fish “melts” at a relatively low temperature. Heating fish thoroughly destroys parasites and microorganisms that live in raw fish, making the fish safer to eat.
How Other Kinds of Processing Affect This Food Marinating. Like heat, acids coagulate the proteins in fish, squeezing out moisture. Fish marinated in citrus juices and other acids such as vinegar or wine has a firm texture and looks cooked, but the acid bath may not inactivate parasites in the fish. Canning. Fish is naturally low in sodium, but can ned fish often contains enough added salt to make it a high-sodium food. A 3.5-ounce ser ving of baked, fresh red salmon, for example, has 55 mg sodium, while an equal ser ving of regular can ned salmon has 443 mg. If the fish is can ned in oil it is also much higher in calories than fresh fish. Freezing. When fish is frozen, ice cr ystals form in the flesh and tear its cells so that mois- ture leaks out when the fish is defrosted. Commercial flash-freezing offers some protec- tion by freezing the fish so fast that the ice cr ystals stay small and do less damage, but all defrosted fish tastes drier and less palatable than fresh fish. Freezing slows but does not stop the oxidation of fats that causes fish to deteriorate. Curing. Fish can be cured (preser ved) by smoking, dr ying, salting, or pickling, all of which coagulate the muscle tissue and prevent microorganisms from growing. Each method has its own particular drawbacks. Smoking adds potentially carcinogenic chemicals. Dr ying reduces the water content, concentrates the solids and nutrients, increases the calories per ounce, and raises the amount of sodium.
Medical Uses and/or Benefits Protection against cardiovascular disease. The most important fats in fish are the poly- unsaturated acids k nown as omega-3s. These fatt y acids appear to work their way into heart cells where they seem to help stabilize the heart muscle and prevent potentially fatal arrhythmia (irregular heartbeat). A mong 85,000 women in the long-run n ing Nurses’ Health Study, those who ate fatt y fish at least five times a week were nearly 50 percent less likely to die from heart disease than those who ate fish less frequently. Similar results appeared in men in the equally long-run n ing Physicians’ Health Study. Some studies suggest that people may get similar benefits from omega-3 capsules. Researchers at the Consorzio Mario Negri Sud in Santa Maria Imbaro ( Italy) say that men given a one-gram fish oil capsule once a day have a risk of sudden death 42 percent lower than men given placebos ( “look-alike” pills with no fish oil). However, most nutrition scientists recom- mend food over supplements. Omega-3 Content of Various Food Fish Fish* (3 oz.) Omega-3 (grams) Salmon, Atlantic 1.8 Anchovy, canned* 1.7 Mackerel, Pacific 1.6 Salmon, pink, canned* 1.4 Sardine, Pacific, canned* 1.4 Trout, rainbow 1.0 Tuna, white, canned* 0.7 Mussels 0.7 * cooked, wit hout sauce * drained Source: Nat ional Fisheries Inst itute; USDA Nut rient Data Laborator y. Nat ional Nut ri- ent Database for Standard Reference. Available online. UR L : http://w w w.nal.usda. gov/fnic/foodcomp/search /.
Adverse Effects Associated with This Food Allergic reaction. According to the Merck Manual, fish is one of the 12 foods most likely to trigger classic food allergy symptoms: hives, swelling of the lips and eyes, and upset stom- ach. The others are berries (blackberries, blueberries, raspberries, strawberries), chocolate, corn, eggs, legumes (green peas, lima beans, peanuts, soybeans), milk, nuts, peaches, pork, shellfish, and wheat (see wheat cer ea ls). NOTE : Canned tuna products may contain sulfites in vegetable proteins used to enhance the tuna’s flavor. People sensitive to sulfites may suf- fer serious allergic reactions, including potentially fatal anaphylactic shock, if they eat tuna containing sulfites. In 1997, tuna manufacturers agreed to put warning labels on products with sulfites. Environmental contaminants. Some fish are contaminated with methylmercury, a compound produced by bacteria that chemically alters naturally occurring mercury (a metal found in rock and soil) or mercury released into water through industrial pollution. The methylmer- cury is absorbed by small fish, which are eaten by larger fish, which are then eaten by human beings. The larger the fish and the longer it lives the more methylmercury it absorbs. The measurement used to describe the amount of methylmercury in fish is ppm (parts per mil- lion). Newly-popular tilapia, a small fish, has an average 0.01 ppm, while shark, a big fish, may have up to 4.54 ppm, 450 times as much. That is a relatively small amount of methylmercur y; it will soon make its way harmlessly out of the body. But even small amounts may be hazardous during pregnancy because methylmercur y targets the developing fetal ner vous system. Repeated studies have shown that women who eat lots of high-mercur y fish while pregnant are more likely to deliver babies with developmental problems. As a result, the FDA and the Environ men- tal Protection Agency have now warned that women who may become pregnant, who are pregnant, or who are nursing should avoid shark, swordfish, king mackerel, and tilefish, the fish most likely to contain large amounts of methylmercur y. The same prohibition applies to ver y young children; although there are no studies of newborns and babies, the young brain continues to develop after birth and the logic is that the prohibition during pregnancy should extend into early life. That does not mean no fish at all should be eaten during pregnancy. In fact, a 2003 report in the Journal of Epidemiology and Community Health of data from an 11,585-woman study at the University of Bristol (England) shows that women who don’t eat any fish while pregnant are nearly 40 percent more likely to deliver low birth-weight infants than are women who eat about an ounce of fish a day, the equivalent of 1/3 of a small can of tuna. One theory is that omega-3 fatty acids in the fish may increase the flow of nutrient-rich blood through the placenta to the fetus. University of Southern California researchers say that omega-3s may also protect some children from asthma. Their study found that children born to asthmatic mothers who ate oily fish such as salmon at least once a month while pregnant were less likely to develop asthma before age five than children whose asthmatic pregnant mothers never ate oily fish. The following table lists the estimated levels of mercury in common food fish. For the complete list of mercury levels in fish, click onto www.cfsan.fda.gov/~frf/sea-mehg.html. Mercury Levels in Common Food Fish Low levels (0.01– 0.12 ppm* average) Anchovies, butterfish, catfish, clams, cod, crab (blue, king, snow), crawfish, croaker (Atlantic), flounder, haddock, hake, herring, lobster (spiny/Atlantic) mackerel, mul- let, ocean perch, oysters, pollock, salmon (canned/fresh frozen), sardines, scallops, shad (American), shrimp, sole, squid, tilapia, trout (freshwater), tuna (canned, light), whitefish, whiting Mid levels (0.14 – 0.54 ppm* average) Bass (salt water), bluefish, carp, croaker ( Pacific), freshwater perch, grouper, halibut, lobster (Northern A merican), mackerel (Spanish), marlin, monkfish, orange roughy, skate, snapper, tilefish (Atlantic), tuna (can ned albacore, fresh/frozen), weakfish/ sea trout High levels (0.73 –1.45 ppm* average) King mackerel, shark, swordfish, tilefish * ppm = parts per million, i.e. parts of mercur y to 1,000,000 parts fish Source: U.S. Food and Drug Administ rat ion, Center for Food Safet y and Applied Nut rit ion, “Mercur y Levels in Commercial Fish and Shellfish.” Available online. UR L : w w w.cfsan.fda. gov/~frf/sea-mehg.ht ml. Parasitical, viral, and bacterial infections. Like raw meat, raw fish may carry various pathogens, including fish tapeworm and flukes in freshwater fish and Salmonella or other microorganisms left on the fish by infected foodhandlers. Cooking the fish destroys these organisms. Scombroid poisoning. Bacterial decomposition that occurs after fish is caught produces a his- taminelike toxin in the flesh of mackerel, tuna, bonito, and albacore. This toxin may trigger a number of symptoms, including a flushed face immediately after you eat it. The other signs of scombroid poisoning—nausea, vomiting, stomach pain, and hives—show up a few minutes later. The symptoms usually last 24 hours or less.
Food/Drug Interactions Monoamine oxidase (MAO) inhibitors. Monoamine oxidase inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyramine, a substance found in many fermented or aged foods. Tyramine constricts blood vessels and increases blood pressure. If you eat a food such as pickled herring, which is high in tyramine, while you are taking an M AO inhibitor, your body may not be able to eliminate the tyramine and the result may be a hypertensive crisis.