Although fish and shellfish are generally low in fat, the small amount of fat they do contain is beneficial. Found almost exclusively in seafood, Omega-3 fatty acids present in fish may play a protective role against heart disease. Omega-3's help keep arteries open by discouraging the build-up of plaque in blood vessels, studies are showing. Preliminary research indicates that Omega-3's can prevent platelets -- cell fragments that help blood to clot -- from sticking together. The result: reduced chance for heart attack or stroke due to blockage in an artery. Omega-3's also are linked to anti-inflammatory effects; early studies indicate that reduced inflamation is more dramatic in the elderly than in younger individuals.
Oilier fish, such as salmon, tuna, mackerel and sardines, contain higher amounts of this "quality fat," but even the lowest-fat fish contain small amounts of these healthy oils.
A medically-supervised study among people who had suffered a heart attack revealed that those who ate about 10 ounces of fat-rich fish per week lived longer than those who did not. Earlier studies have indicated that eating fish two or three times a week and maintaining a low-fat diet extends life.
High-fat diets have been linked to 5 of the 10 leading causes of death in the United States, including heart disease and cancer of the colon, breast, and prostate. In California, 36,000 premature deaths and $5 billion in health care costs in 1986 were attributed to the typical high-fat, low-fiber American diet, noted State Health Director Molly Coye, MD, MPH, announcing a statewide 1993 program to reduce dietary fat, California Project L.E.A.N. (low-fat eating for America now). A 3-ounce serving of seafood provides approximately half of the recommended daily intake of protein, yet contains the lowest level of saturated fat in any muscle meat available.
Recent research indicates that eating a low-fat dinner, such as seafood, sharply reduces the risk of a heart attack the following morning. Studies suggest that high-fat meals put the blood into a hypercoagulation state within six or seven hours, raising the risk of dangerous, artery-clogging blood clots, the cause of many heart attacks. Fatty meals activate a blood-clotting substance called factor VII. The higher the level of factor VII, the greater the probability of clotting. Most heart attacks occur in the early morning, and doctors theorize that a possible cause could be hyper-coagulation of the blood. Another study revealed that individuals who switched from a high-fat to a low-fat diet reduced their factor VII activity significantly. This research reconfirms a finding that low-fat diets reduce cholesterol deposits over the long term and reduce the risk of blood clots -- and heart attacks -- almost immediately.
A comprehensive study among more than 88,000 women concluded that a high intake of animal fat increases the risk of colon cancer. The study recommended substituting fish and chicken for diets high in fat.
"Shellfish and marine animals such as lobster, crab, shrimp, clams, oysters, scallops, and abalone have little or no effect on the plasma cholesterol concentration because they are low in fat." American College of Physicians, 1988.
Saturated fat -- not dietary cholesterol -- is the main culprit in raising blood cholesterol. Saturated fat is what turns the body on to making cholesterol. High levels of cholesterol in the blood can lead to blocked arteries, heart attacks, and strokes.
Shellfish received an unfair reputation for high cholesterol because of outdated scientific methods that detected cholesterol-like substances as well as cholesterol. The resulting readings were falsely high.
A serving of most any shellfish is well within the 300-mg daily intake level recommended by major health organizations, including the American Heart Association and National Academy of Sciences. Although crustaceans such as shrimp, lobster, and squid, are higher in dietary cholesterol than mollusks such as clams, oysters, mussels, and scallops, they are extremely low in saturated fat, and doctors see no reason to avoid them.
Prominent heart experts no longer place limitations on specific shellfish for their patients with high blood cholesterol levels as long as portion sizes are not excessive and patients watch their saturated fat intake.
Content of 3.5 oz (100 g) portions of raw shellfish
Source: U.S. Department of Agriculture, Human Nutrition Information Service Handbook 8-15
For the best growth and development of children, pregnant and nursing women need adequate amounts of Omega-3's. Preliminary studies suggest that Omega-3's may be important for optimal visual development early in life.
Doctors recommend that the general population, including pregnant and nursing mothers, eat seafood two or three times a week.
Pregnant women need more protein, and seafood is an excellent low-fat protein source. Women may boost their calcium intake by eating sardines and mackerel canned with bone in. Clams, mussels, and oysters are higher in iron than red meat. Oysters, crab, and lobster are good sources of zinc, another mineral required in greater amounts during pregnancy and lactation.
"If a pregnant or breastfeeding woman consumes commercially harvested seafood, I see no cause for concern, particularly if she eats a variety." Robert Price, PhD., seafood safety expert, University of California at Davis.
Other experts concur with Dr. Price, finding seafood to be a great source of nutrition for pregnant and breastfeeding women.
FDA officials have testified that pound-for-pound, fish is by far the safest source of muscle protein available.
During pregnancy and breastfeeding, it makes sense to take a few common-sense precautions. Following are suggestions that appeared in the National Academy of Sciences 1991 report, Seafood Safety.
Avoid eating raw and undercooked fish and shellfish.
Keep fish and shellfish refrigerated or frozen until ready to use.
Eat a variety of all types of foods including fish and shellfish.
Pregnant and breastfeeding women should limit consumption of shark, swordfish and fresh tuna to once a month.
* Pregnant women, nursing mothers, and young children in particular, heed advisories that accompany sportfishing licenses not to eat certain species of recreationally-caught fish from inland waters because of chemical concerns.