Seafood and Your Health

Nutritionists have known for decades that seafood is a low-fat source of top-quality protein, and that the health benefits of eating seafood make it one of the best choices for growing children, active adults, and the elderly. Recent studies show that eating seafood can decrease your risk of heart attack, stroke, obesity, and hypertension. The following information is brought to you by NOAA, the U.S. Food and Drug Administration, the U.S. Department of Agriculture, and the Environmental Protection Agency.

Shopping for Seafood
Catching Your Own: Tips for Staying Safe
Tips for Storing Seafood to Preserve Quality
Cooking and Serving Safe, Healthy Seafood
Important Health Notes
For Moms and Moms to Be
About Nutrition
Frequently Asked Questions

Shopping for Seafood
Buying your seafood from a store that follows basic food handling rules helps ensure that the seafood you buy is of the highest quality and safe to eat. Use careful shopping sense when visiting the seafood counter and fish monger's stand, paying close attention to the overall cleanliness of the facility and condition of the fish. Use these simple steps to ensure the seafood you buy is the healthiest, highest quality product possible.

Selecting Fresh Fish

Why Freshness Counts Healthwise, it is important to look for freshness when choosing seafood. In some species, if the catch has been left out in the sun too long or if the fish haven't been transported under proper refrigeration, toxins known as scombrotoxin, or histamine, can develop. Eating spoiled fish that have high levels of these toxins can cause illness.

The Frozen Section: How to select frozen fish
Today, fresh catches can be processed and frozen immediately to very low temperatures - frequently, this takes place right on the fishing vessel. However, frozen seafood can spoil if the fish thaws during transport and is left at warm temperatures for too long. To help ensure that the frozen fish you're buying is safe, follow these guidelines:

Selecting Shellfish: Special guidelines
The Food and Drug Administration requires shellfish harvesters and processors of oysters, clams, and mussels to put a tag on sacks or containers of live shellfish (in the shell), and a label on containers or packages of shucked shellfish. Tags and labels contain specific information about the product, including a certification number for the processor, which means that the shellfish were harvested and processed in accordance with national shellfish safety controls. Ask to see the tag or check the label when purchasing shellfish.

In addition, follow these general guidelines:

Catching Your Own: Tips for staying safe
Before: Always check local advisories and sign postings for information about the safety of fish and shellfish in your area. Always obey local and federal fishing regulations!
During: Be sure to keep fish and shellfish well iced while fishing and while transporting the seafood home.
After: Fish caught in some lakes and streams may have harmful levels of Polychlorinated Biphenyls or PCBs, which can cause a variety of health problems.* Since PCBs accumulate in fat, trim the fat and skin from fish before cooking. This can lessen the risk of exposure to these contaminants. Broil, grill, or bake the trimmed, skinned fish on a rack so the fat drips away.
* Harmful levels of PCBs have not been found in fish that are sold in the commercial marketplace, including farm-raised species.

Tips for Storing Seafood to Preserve Quality
Put seafood on ice or in the refrigerator or freezer soon after buying it, using these guidelines for safe storage: if seafood will be used within two days after purchase, store it in the refrigerator, but, if seafood won't be used within two days after purchase, wrap it tightly in moisture-proof freezer paper or foil to protect it from air leaks and store it in the freezer.

Cooking and Serving Safe, Healthy Seafood
Preparing Seafood
Thawing It Safely 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.

Preventing Cross-Contamination When you're preparing fresh or thawed seafood, it's important to prevent bacteria from the raw seafood from spreading to ready-to-eat food. Take these steps to avoid cross-contamination between raw and cooked foods:

Cooking It Properly Most seafood should be cooked to an internal temperature of 145 °F. But, if you don't have a food thermometer, there are other ways to determine whether seafood is done.

   Fish: Slip the point of a sharp knife into the flesh and pull it aside. The flesh    should be opaque and separate easily. If you cooked the fish in the microwave,    check it in more than one spot to help ensure it is completely cooked    throughout.
   Shrimp and Lobster: The flesh becomes pearly-opaque.
   Scallops: The flesh turns milky white or opaque and firm.
   Clams, Mussels, and Oysters: Watch for the point at which their shells open,    which means they're done. Throw out the ones that don't open.

Serving Seafood
Don't Cross-Contaminate Cross-contamination can happen once your seafood is cooked, too. Here are simple ways to keep your seafood safe when serving:

Temperature Counts Follow these serving guidelines once your seafood is cooked and ready to be enjoyed.

Eating it Raw
It's always best to cook seafood thoroughly to minimize the risk of foodborne illness. However, if you choose to eat raw fish anyway, one rule of thumb is to eat fish that has been previously frozen. Some species of fish can contain parasites, and freezing will kill any parasites that may be present. However, be aware that freezing doesn't kill all harmful microorganisms. That's why the safest route is to cook your seafood.

An Important Note About Oysters: Some oysters may have to be treated after harvesting to eliminate naturally occurring harmful bacteria. This information may or may not be on the label. Since not all post-harvest treatments are equally effective in eliminating harmful bacteria, raw oysters should avoided by people at risk for foodborne illness.

Important Health Notes
Keep in mind that some people are at greater risk for foodborne illness, and should not eat raw or partially cooked fish or shellfish. These susceptible groups include:

   Pregnant women
   Young children
   Older adults
   Persons whose immune systems are compromised
   Persons who have decreased stomach acidity

If you are unsure of your risk, ask your healthcare provider.

Smoked Seafood: Avoiding Listeriosis Pregnant women, older adults, and people with weakened immune systems have an increased chance of getting a foodborne illness called listeriosis. If you are in one of these groups, there is a simple step you can take to reduce your chance of contracting the listeriosis disease from seafood: Avoid refrigerated types of smoked seafood except in a cooked recipe, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna, or mackerel, is usually labeled as "nova-style", "lox", "kippered", "smoked", or "jerky" and can be found in the refrigerated section of grocery stores and delicatessens. They should be avoided. You needn't worry about getting listeriosis from canned or shelf-stable smoked seafood.

For Moms and Moms-to-Be
If you are pregnant, nursing your child, or thinking about becoming pregnant, it is important that you avoid consuming too much methylmercury. This substance can be found in certain fish, and it can harm an unborn child's developing nervous system if eaten regularly.

Don't Eat . . .
Avoid these four fish species:
   Shark
   Swordfish
   King mackerel
   Tilefish

However, don't deny yourself or your unborn baby the nutritional benefits of fish - you can eat 12 ounces (two average meals) a week of other types of cooked fish, as long as you eat a variety of kinds that are lower in mercury. This same advice should be followed when you're feeding fish and shellfish to your young child, but serve smaller portions.

Do Eat . . .
Five of the most commonly eaten fish that are low in mercury are:
   Shrimp
   Canned light tuna*
   Salmon
   Pollock
   Catfish

"Local Catch" Alert: Be sure and check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas.

*Another commonly-eaten fish, albacore ("White") tuna, has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.

By following the basic food safety tips for buying, preparing, and storing fish and shellfish you and your family can safely enjoy the fine taste and good nutrition of seafood.

For more information see:
What You Need to Know About Mercury in Fish and Shellfish March 2004
Food Safety for Moms-to-Be August 2005
Vibrio vulnificus Health Education Kit March 2004

About Nutrition
Seafood is an important part of a healthful diet. Seafood contains high-quality protein and other essential nutrients, is often low in saturated fat, and contains omega-3 fatty acids. In fact, a well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children's growth and development. But, as with any type of food, it's important to handle seafood properly in order to reduce the risk of foodborne illness. Follow these basic food safety tips for buying, preparing, and storing fish and shellfish, and you and your family can safely enjoy the fine taste and good nutrition of seafood.

How much seafood should we eat? A Dutch study published in May 1985 in the New England Journal of Medicine concluded that "the consumption of as little as one or two fish dishes a week may be of preventive value in relation to heart disease". These findings were echoed by scientists who gathered at a two-day conference on seafood and health in November 1985. They agreed that eating several seafood meals a week is a good way to cut your risk of heart disease. "I have no qualms about the American public eating three or even four meals of fish a week," said Dr. William Castelli, director of the Framingham Heart Study.

Protein
Proteins are large molecules composed primarily of amino acids. Our body's digestive enzymes break down the protein we consume to release amino acids, which are in turn used to make new proteins for the body to use for growth and maintenance. There are nine amino acids which the body cannot manufacture; we must get them from food. They are called essential amino acids. Seafood contains all nine essential amino acids; therefore, it is an excellent choice for meeting our daily protein needs. An added advantage of seafood is that its protein is highly digestible. The protein in seafood is more readily broken down and absorbed than the protein in red meats and poultry. This advantage makes seafood an excellent food choice for people of all ages. Fish contain 17 to 25% protein, with an average protein content of 19%.

Fat and Calories
What is a calorie? Many people count calories or weight-watch, but do they really understand what they are counting? The food calorie or kilogram calorie is a measure of energy, defined as the quantity of thermal energy required to raise one gram of water by 1 degree Celsius at a temperature of 15 degrees Celsius. The calories in food supply the energy the body needs to carry out all its many functions. The nutrients in food that supply energy are fat (nine calories per gram) and carbohydrates and proteins (four calories per gram each). Most varieties of finfish and shellfish are low in fat (less than 5%) and, in many cases, less than 1% fat. Therefore, most varieties of seafood provide 100 to 200 calories per 3.5 ounces.

The Dietary Guidelines published by the USDA and the Department of Health and Human Services advise us to eat less total fat. More specifically, they say to reduce overall fat consumption from approximately 40 to 30% of energy intake. This means that of all the calories we derive from the food we eat, only 30% of them should come from fat. The Dietary Guidelines go on to suggest the type of fat. "Reduce saturated fat consumption to account for about 10% of total energy intake, and balance that with polyunsaturated and monounsaturated fats, which should account for about 10% of energy intake each." Seafood goes a long way in helping consumers achieve these U.S. dietary goals. The total amount of fat in most varieties of seafood is very low, and the fat is rich in polyunsaturated fatty acids. Typically, the way seafood is prepared adds fat, such as with sauces and deep-fat frying. Cooking techniques such as broiling, barbecuing, poaching, microwaving, or steaming on a rack will help reduce the amount of fat in the total fish recipe. Increasing the intake of fish is compatible with a reduction of calorie intake and saturated fatty acid intake.

Vitamins and Minerals
There are two types of vitamins, fat soluble (A, D, E, and K) and water soluble (C and the B complex). Vitamins A and D are found in fish liver oils and in small amounts in the fatty tissues of fish. Seafood is generally low in fat, and we usually don't consume fish liver oils; therefore, seafood is not considered a significant source of the fat-soluble vitamins. There is little Vitamin C found in seafood, but it is considered an excellent source of the B complex vitamins, particularly niacin, B12 and B6. Fair amounts of thiamine are also found in seafood.

Seafood is an excellent source of minerals. Fish are one of the most important sources of calcium. The soft bones of small fish such as sardines and smelts and canned varieties such as salmon are especially valuable sources of calcium. Other minerals in seafood include zinc (oysters and crustaceans), iron (oysters, bluefish, and shrimp), copper (oysters, crabs, and lobster), potassium (mussels, scallops, and clams), and iodine, phosphorus, and selenium (all seafood in general). Fresh seafood is low in sodium. For those who have to restrict the intake of sodium, fresh seafood is an excellent choice, although you should limit your intake of processed seafoods such as smoked, cured, and most canned seafoods. Salt is added in the processing of these seafood products as it is in imitation seafood products.

Cholesterol
Cholesterol levels are not significant in most seafood products. Finfish are generally quite low in cholesterol, with shellfish having low to moderate amounts. In the past, shellfish have been excluded from low cholesterol diets because they were believed to be high in cholesterol. New sophisticated measuring techniques have indicated that cholesterol levels of many molluscan shellfish are much lower than previously thought. In fact, mollusks, such as clams, oysters, scallops, and mussels, were found to have a large percentage of noncholesterol sterols present that appear to have a positive effect. These sterols inhibit the absorption of cholesterol eaten at the same meal. Cholesterol levels in crustaceans such as crab and lobster are similar to levels found in the dark meat of chicken. While the cholesterol in shrimp varies considerably by species, it generally is 1-1/2 to 2 times higher than the cholesterol in the dark meat of chicken, but far less than in eggs. Because shellfish contain very little saturated fat, they are no longer excluded from typical low-cholesterol diets.

Again, seafood fits right in when trying to meet the U.S. dietary goal - reduce cholesterol consumption to about 300 milligrams a day. Fish averages about 50-90 milligrams cholesterol per 3.5 ounces. Shellfish tend to contain slightly higher amounts of cholesterol; crustaceans (crab, lobsters, and shrimp) contain 60-100 milligrams per 3.5 ounces and mollusks (clams, oysters, scallops) contain 40-110 milligrams per 3.5 ounces. Squid and octopus may contain relatively high levels, 250 and 122 milligrams per 3.5 ounces, respectively.

More about Omega-3 Fatty Acids
The above indicates that seafood consumption is a good idea that is compatible with optimum dietary practices/recommendations and that substitutions of fish for other foods can help maintain a balanced nutrient intake compatible with a low-fat diet. The consumption of fish oils may provide added significant health benefits. In fact, NOAA's National Marine Fisheries Service (NMFS) scientist Maurice Stansby was the first to discover the nutritional benefit of fish oils. The only NMFS scientist to receive the President's Award for Distinguished Civilian Service, Stansby published a book on the subject called Fish Oils in Nutrition in 1990.

Fish oils may provide a protective effect in minimizing the development of several chronic degenerative diseases and may have a therapeutic effect in certain cases like arthritis, atherosclerosis, and vasospasm.

Fish oils are composed of fatty acids which consist of a chain of carbon atoms with a carboxyl group at one end and a methyl group (CH₃) at the other. Polyunsaturated fatty acids (PUFA) contain several double bonds between carbon atoms in the chain; the more double bonds, the higher the degree of unsaturation. Fish oils are unique in that they contain a large portion of highly unsaturated fatty acids and some fatty acids with an odd number of carbons in the chain.

Many fish oils are composed primarily of omega-3 fatty acids. They differ from most plant oils which contain mainly omega-6 fatty acids. The most important omega-3 fatty acids found in seafood are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fish and shellfish ingest and accumulate omega-3 fatty acids through the food chain from algae and phytoplankton, the primary producers of omega-3 fatty acids. The human body can only produce saturated and omega-9 fatty acids which means we have to get the omega-3 fatty acids we need through our daily foods.

How do omega-3 fatty acids prevent or cure human diseases? After several medical studies, it now appears that omega-3 fatty acids help keep our bodies from over-producing eicosanoids, a group of hormone-like substances that can, in large amounts, contribute to arthritis, asthma, heart disease, stroke, and related disorders. The eicosanoids are normally derived from the omega-6 PUFA arachidonate, found predominantly in plant oil. Omega-3 fatty acids act as an antagonist to eicosanoid synthesis, thereby lowering their production. It also forms modified eicosanoids less active than the normal compounds. A diet that balances plant foods with fish foods and their omega-3 fatty acids, remains an effective and enjoyable way to combat health problems.

Most nutrition researchers now say that eating seafood once or twice a week may be beneficial in preventing heart disease. The high content of PUFA in seafood lowers serum cholesterol levels. Omega-3 fatty acids change the critical balance of certain blood components called lipoproteins, thus reducing the low-density lipoproteins (LDL) and very low density lipoproteins (VLDL) that deposit cholesterol along the artery walls. Omega-3 fatty acids also lower the levels of triglycerides, another type of fat involved in heart disease. They also form a different pattern of prostaglandin, diminishing the clotting of blood cells, reducing the number and stickiness of blood platelets, and making red blood cells more flexible so that they flow more smoothly.

Other health problems that may be controlled or alleviated by the consumption of omega-3 fatty acids from fish are asthma, arthritis, diabetes, multiple sclerosis, hypertension, migraine headaches, cancer, and some kidney diseases.

"Do Your Health a Favor, Eat Seafood"
Fresh seafood is an excellent source of protein, a good source of minerals and some vitamins, and is low in fat, cholesterol, and sodium. In general, seafood is one of the most nutritionally balanced foods. A seafood diet helps control weight and goes a long way toward preventing heart disease. Besides, a seafood diet is a delicious way to accomplish heart-healthy eating habits.

Seafood and Health FAQs
From the U.S. Food and Drug Administration's Seafood Information and Resources

Q: How can you select safe seafood?
A:

Q: How can you figure out if the fish is fresh?
A: The fish's eyes should be clear and bulge a little. Only a few fish, such as walleye, have naturally cloudy eyes. Whole fish and fillets should have firm and shiny flesh. Dull flesh may mean the fish is old. Fresh whole fish also should have bright red gills free from slime. If the flesh doesn't spring back when pressed, the fish isn't fresh. There should be no darkening around the edges of the fish or brown or yellowish discoloration. The fish should smell fresh and mild, not fishy or ammonia-like.

Q: What fish should pregnant women avoid?
A: Seafood can be an important part of a balanced diet for pregnant women. It is a good source of high-quality protein and other nutrients and is low in fat. However, some fish contain high levels of a form of mercury called methylmercury that can harm an unborn child's developing nervous system if eaten regularly. By being informed about methylmercury and knowing the kinds of fish that are safe to eat, you can prevent any harm to your unborn child and still enjoy the health benefits of eating seafood.

The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) are advising women who are or may become pregnant, nursing mothers, and young children to avoid some types of fish and to eat fish and shellfish that are lower in mercury. By following these three recommendations for selecting and eating fish or shellfish, women and young children will receive the benefits of eating fish and shellfish and be confident that they have reduced their exposure to the harmful effects of mercury.

Follow these same recommendations when feeding fish and shellfish to your young child, but serve smaller portions.

Q: How does mercury get into fish?
A: Mercury occurs naturally in the environment, and it can also be released into the air through industrial pollution. Mercury falls from the air and can get into surface water, accumulating in streams and oceans. Bacteria in the water cause chemical changes that transform mercury into methylmercury that can be toxic. Fish absorb the methylmercury as they feed in these waters and so it may build up in them. It builds up more in some types of fish and shellfish than others, depending on what the fish eat, which is why the levels in the fish vary.

Q: How can you spot a safe seafood seller?
A: Anyone who's ever smelled rotting seafood at the fish counter has a pretty good idea of what a poorly run seafood market smells like. But the absence of any strong odor doesn't necessarily mean that the seller is practicing safe food handling techniques. Based on FDA's Food Code, here are some other points to consider: Employees should be wearing clean clothing, but no outerwear, and wearing hair coverings. They shouldn't be smoking, eating, or playing with their hair. They shouldn't be sick or have any open wounds. Employees should be wearing disposable gloves when handling food and change gloves after doing nonfood tasks and after handling any raw seafood.

Fish should be displayed on a thick bed of fresh, not melting, ice, preferably in a case or under some type of cover. Fish should be arranged with the bellies down so that the melting ice drains away from the fish, thus reducing the chances of spoilage.

Ask yourself: What's your general impression of the facility? Does it look clean? Smell clean? Is it free of flies and bugs? A well-maintained facility can indicate that the vendor is following good sanitation practices.

Also, is the seafood employee knowledgeable about different types of seafood? Can he or she tell you how old the products are and explain why their seafood is fresh? If they can't, you should take your business elsewhere.

Q: How can I avoid seafood fraud?
A: To get the best value for your money when buying seafood, it's important to know what you're buying. Be wary of unusual bargains - some seafood is seasonal. If there is a considerable difference between the price of a fresh product and what you are accustomed to paying, it could be that it is from the last season's frozen inventory. Buy from a reputable dealer. And if the fish you choose looks or smells different from what you expect, discuss it with the fish market manager. Look for firm, shiny flesh that bounces back when touched. If the head is on, the eyes should be clear and bulge, and the gills should be bright red. The fish should not smell "fishy" - it should smell like a fresh ocean breeze.

It's easy to miss the telltale signs of species substitution. Sometimes, taste or consistency is the only way to detect it. If you feel you have purchased something different from what was represented, tell your fish market manager. Here's how to distinguish some common species:
   Haddock has a dark lateral line along the skin surface.
   Skinless cod fillets have a distinctive white papery membrane along the belly    and a white line of fat along the lateral line of the fillet.
   Shark and swordfish look alike, but shark has a dark streak of flesh in the    center and rough skin along the edge.
   Red snapper comes only from the southern Atlantic Ocean and the Gulf of    Mexico (ask your retailer where the snapper originated).
   Orange roughy comes only from Australia or New Zealand and always arrives    frozen. It may be sold thawed, but it must be labeled as previously frozen.
   Scrod is not a type of fish. The term originated in the Boston area to describe    the catch of the day. It is a fish under two and a half pounds that is either cod,    haddock or pollock. Such fish should be labeled in the market or listed in a    restaurant as "scrod cod," "scrod haddock," or "scrod pollock."

Q: What about the fish caught by my family or friends in freshwater lakes and streams? Are they safe to eat?
A: There can be a risk of contamination in freshwater from either natural or industrial causes that would make the fish unsafe to eat. The Environmental Protection Agency provides current advice on fish consumption from freshwater lakes and streams. Also check with your state or local health department to see if there are special advisories on fish caught from waters in your local area.