Seafood is a very good source of minerals, especially some of those harder-to-get trace minerals such as iodine, selenium, and zinc. Oysters are especially high in zinc, while crab and lobster are also fairly high; selenium is present in high amounts in most of the shellfish and mollusks and in codfish. Most fish are high in potassium and phosphorus. Iron levels are usually very good, and calcium can be high, especially if bones are consumed, as in sardines, and in salmon, shrimp, and herring. Calcium is actually higher in the seaweeds or sea vegetation, which are ideal foods to eat with fish. This is done commonly in Japan, and it makes good sense.

A wide variety of fish are eaten throughout the world. I will briefly discuss some of the main categories and some specific fish that are common to our Western diets.

Shellfish consist of a variety of small meaty and mineral-rich fish from two families, the mollusks and the crustaceans. The mollusks animals that are the sea filters, or "garbage eaters," as I call them. These include clams, oysters, mussels, and scallops. I usually suggest that people avoid eating much of these foods. Since these shellfish eat by pumping water through their bodies, they can easily concentrate pollutants from the ocean. Whenever there is water contamination, it is specifically suggested that these fish be avoided. They can pick up chemicals, heavy metals such as mercury, and germs from sewage, for example. The mollusks can be delicious and very high in nutrients, but unless they come from waters known to be very clear, they are risky foods to eat and can be toxic.

The crustaceans are of less concern. They are not sea filters and live in deeper and usually cleaner waters than the mollusks. The major crustaceans, or soft-shelled fish, are crabs, lobsters, and shrimp. As mentioned before, these shellfish had been avoided because they were thought to be too high in cholesterol, but it turns out that what they contain is not all cholesterol but a mixture of lipids. Crustaceans are also fairly low in calories and high in protein and are used commonly, as are most fish, by people who are trying to lose or maintain weight. However, some religions, such as Judaism, forbid the consumption of crustaceans.

• Vitamins A?swordfish, whitefish, crab, halibut, salmon
• B vitamin?crab, salmon, trout, halibut, mackerel, oysters
• Vitamin B12?herring, mackerel, salmon, oysters, trout, crab
• Vitamin E?herring, mackerel, haddock
• Calcium?salmon, sardines, shrimp, oysters, herring
• Copper?oysters, lobster, shrimp, crab, trout Iodine?most salt-water fish
• Iron?oysters, abalone, carp, perch, salmon, scallops, shrimp, trout
• Magnesium?mackerel, oysters, salmon, snails, shrimp, crab?generally low; some in snails and oysters
• Phosphorus?cod, trout, halibut, perch, scallops, snapper, salmon
• Potassium?cod, trout, halibut, perch, scallops, snapper, salmon
• Selenium?lobster, scallops, shrimp, oysters, cod
• Sodium?shrimp, lobster, mackerel, herring
• Zinc?oysters, lobster, crab, halibut

The most nutritious fish overall I think are halibut, swordfish, and, probably, tuna, flounders, seabass, and cod from the sea, with some freshwater trout, whitefish, or perch and occasionally salmon or mackerel as the higherfat, more caloric fish. Most of these fish are very high in protein, variable in fat, and low in carbohydrates. They vary in calories from about 400-800 per pound. The fattier fish, such as salmon, mackerel, eel, herring, and trout, often have twice the calories of the less fatty fish and the shellfish. So even though these are thought to be helpful fats, the calorie count can lead to increased weight.