Fish is now the preferred food of people who wants to stay healthy, white fish in particular is more easily digested than meat, therefore it is ideally for people with digestive problems. Unlike meat, the fat in fish consists mostly of oils containing unsaturated fatty acids. The essential fatty acids in oily fish are of benefits to health.

Classification of fish according to their origin:

• Freshwater fish, e.g. salmon, trout;
• Seawater fish, which are further divided into; pelagic fish (which swim near the surface) and demersal fish (which swim near the bottom).

Classification and Health Benefits of Fish:

• Oily fish: Oily fish like mackerel, salmon, tuna have more than 5% fat (mostly omega-3) in their flesh. All omega-3 fats are essential for healthy cells, brain development, cognitive function and general good health. As well as offering vitamin D, canned sardines is an excellent source of calcium as you can eat the bones. Canned tuna contains much less vitamin D and essential fatty acid than the fresh fish as its oil is removed before canning and is sold separately. Avoid fish canned in vegetable oil as this blend may contain a lot of saturated fat. Only buy fish that has been canned in olive, sunflower or soya-bean oil. If you suffer from any other forms of arthritis, however, you will find oily fish extremely helpful as they have a potent anti-inflammatory action, which can relieve joint and muscle pains.

• White Fish: They all contain virtually no fat, few calories and plenty of protein as well as the B vitamins. They don't however, contain much iron and though halibut, which is slightly oily, may contribute a little vitamin A, the white fish do not generally supply fat-soluble vitamins. The livers of cod and halibut are very rich in vitamins A, D and E, but these aren't eaten, only used for the production of oil. The roe of white fish is an excellent source of B vitamins and as a good source of iron and some meat, but fish roe contains cholesterol so may not be suitable for people with inherited disorders of fat metabolism or very high cholesterol levels.
• Shellfish, which are divided into: mollusks (small, soft-bodied sea animals which live inside a hard shell) e.g mussel; crustaceans (soft-bodied, jointed sea animals which are covered by a hard protective "crust" or external skeleton), e.g lobster, crap, shrimp.

Nutritive Value of Fish:

• Protein: 19.0% (oily fish); 17.5% (white fish); 15% (shellfish edible part)
• Fat: 15.0% (oily fish); 0.9% (white fish); 4% (shellfish edible part)
• Water: 67.5% (oily fish); 80.0% (white fish); 8.5% (shellfish edible part)
• Minerals: 2.5% (oily fish); 1.2% (white fish); 1.4% (shellfish edible part)

How to choose fish: As fresh fish deteriorates rapidly, it is important to choose it carefully. Fresh fish should have:

• Bright eyes and shiny, not sunken.
• Plump, firm flesh
• Plenty of bright scales, firmly attached to the skin
• Moist skin
• A fresh, sea smell
• Bright red gills, not sunken

How to choose shellfish: When buying shellfish check that they feel heavy for their size. All mollusks should be closed and all shellfish should be eaten on the day you buy them. Above all, buy your shellfish from a supplier whose reputation you can rely on.

Cooking Fish: Fish has a muscle composition similar to that of meat, but there is far less connective tissue, so it is much easier to tenderize and quicker to cook. It is important not to overcook fish as the protein easily becomes tough and the flesh dry. The muscle is formed into flakes which separate on cooking. The best ways to cook fish are baking, steaming, grilling, or pan-frying in shallow oil, as all these methods minimize the loss of nutrients. Boiling fish results in considerable loss of minerals, especially iodine, but as long as you use the cooking water to make sauce for your fish dish, you won't lose out.

Storage: Fish should be eaten as soon as possible after purchase, and should be stored in the coldest part of the refrigerator (but not the ice box), well wrapped, to prevent the strong odors from contaminating other foods.

Caution:

• Fish and shellfish are fairly a common cause of severe food allergy. If you experience allergic reaction when you eat fish be careful the next time.
• Some fish are rich in a group of chemicals called purines, which can severely aggravate the painful symptoms of gout. Sufferers of gout should therefore avoid cod and herring roe, caviar, mackerel, scallops, and mussels.