Fish on the menu: why eat it and how to choose it

Fish is one of the few animal foods that delivers complete protein, heart-protecting fatty acids and vitamins that are often in short supply on an Estonian’s plate. With roughly 20% protein, fish is easy to digest and suits almost any menu.

Why fish belongs in your weekly menu

Like meat and egg protein, fish protein is complete — it contains all the essential amino acids. Connective tissue makes up only 2-5% of fish protein, which is why the flesh is tender and fish dishes are easy to digest.

Fat content varies greatly from species to species. Lean fish — cod, perch, pike, pikeperch, roach — contain about 1% fat and are therefore well suited to a diet. Eel, herring and salmon are considerably fattier. Even within a single species, fat content fluctuates with the season: Baltic herring contains 3-4% fat in spring and almost twice as much in autumn. The fattiest part is usually the liver, followed by the area under the skin and the abdominal cavity.

For comparison, here is the energy content per 100 g:

• Pork — 324 kcal/100g
• Broiler chicken — 191 kcal/100g
• Baltic herring — 103 kcal/100g

Even fatty fish dishes contain fewer calories than fatty meat. Fish does contain cholesterol too — the fattier the fish, the more. Salmon’s cholesterol content is similar to pork’s, while smoked eel carries about twice as much. Fish roe and crustaceans are also rich in cholesterol.

Heart-friendly fish and omega-3

Fish fat differs significantly from other animal fats: it is rich in long-chain omega-3 fatty acids, the most important of which are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Most of the polyunsaturated fatty acids in other animal and plant fats belong to the omega-6 group (linoleic acid, arachidonic acid).

Omega-3 has a favorable effect on the composition of your blood — it raises HDL, or “good cholesterol,” and lowers LDL and triglycerides. High LDL and triglyceride levels are risk factors for cardiovascular disease. In addition, omega-3 fatty acids inhibit the formation of blood clots and strengthen the immune system.

That doesn’t mean it’s worth taking lots of fish oil capsules. Overconsumption can cause blood clotting disorders, and with fish oil the body can get too much vitamin A and D, which are toxic in large amounts. The simple truth: 2-3 fish meals a week provide the omega-3 you need without side effects. Among the Eskimos, who eat a great deal of fish, heart attack, diabetes and asthma are almost unknown.

Vitamins and minerals in fish

Fish is rich in the fat-soluble vitamins A, D, E and K. Fattier species contain more of them. Vitamin D is especially valuable, as it is in short supply in the typical Estonian diet. The body can synthesize vitamin D itself under ultraviolet radiation, but sunny days are few in Estonia. Vitamin D in turn helps the body absorb calcium, and calcium deficiency is a serious problem here — spontaneous bone fractures already occur in children and young conscripts, not to mention women past childbearing age.

Of the water-soluble vitamins, fish contains mainly B1, B2, B6 and niacin. Some examples per 100 g:

• Eel: vitamin A 1800 µg, D 30 µg, E 8.0 mg, B1 0.15 mg, B2 0.31 mg
• Salmon: A 15 µg, D 13 µg, E 2.2 mg, B1 0.23 mg, B2 0.10 mg
• Baltic herring: A 12 µg, D 9.2 µg, E 2.0 mg, B1 0.11 mg, B2 0.16 mg
• Rainbow trout: A 23 µg, D 9.0 µg, E 0.8 mg, B1 0.23 mg, B2 0.10 mg
• Vendace: A 96 µg, D 9.2 µg, E 1.5 mg, B1 0.07 mg, B2 0.07 mg

Among minerals, the muscle tissue of fish contains calcium, phosphorus and magnesium. There is even more calcium and phosphorus in the bones — so it’s worth eating fried Baltic herring or a Baltic herring bake together with the bones. When fish is canned, the bones soften and become a good source of minerals. The most important trace elements are iodine (for normal thyroid gland function), selenium (an antioxidant that also protects the fish’s lipids from oxidation), iron and zinc.

• Eel: calcium 430 mg, phosphorus 390 mg, iodine 60 µg, selenium 57 µg
• Vendace: calcium 190 mg, phosphorus 290 mg, iodine 25 µg, selenium 26 µg
• Rainbow trout: calcium 130 mg, phosphorus 260 mg, iodine 15 µg, selenium 18 µg
• Baltic herring: calcium 71 mg, phosphorus 200 mg, iodine 30 µg, selenium 18 µg
• Salmon: calcium 16 mg, phosphorus 240 mg, iodine 65 µg, selenium 26 µg

How to choose fresh fish and store it

Fish spoils easily. The microbes of live fish are psychrophiles, which multiply in the cold. Microbes are found in the slime layer and the intestines, but not in the muscle tissue of a healthy fish. After death, digestive enzymes keep working, the bellies of some fish can rupture, and the compounds that form are in turn an excellent breeding ground for bacteria.

Temperature is the deciding factor in spoilage. Even at 0°C the number of psychrophiles grows. At room temperature, the number of spoilage bacteria doubles in just 20-30 minutes. You can recognize fresh fish like this:

• The fish is firm
• It smells fresh
• The color is typical of the species
• The gills are light red
• The slime layer is even
• The backbone stays firmly attached to the muscles

One of the more dangerous bacteria is Clostridium botulinum, whose toxin is the strongest of all natural poisons. Bacteria that produce toxin E have been found in the intestines of fish, and the toxin forms at temperatures as low as +3°C. Vacuum packing promotes its development. The spores are destroyed only by autoclaving, while the toxin itself is destroyed at +80°C in 30 minutes. The only safe way to store fish is to keep it below 3°C.

Fish can contain heavy metals (mercury, arsenic), organochlorine compounds and dioxins. The older and fattier the fish, the greater the risk of contamination. Choose younger fish, for example Baltic herring no longer than 17 cm. Fish caught in Estonian lakes, especially Lake Peipus (pike, perch, pikeperch, ruffe), may contain the fish tapeworm (Diphyllobothrium latum), which also infects humans if the fish has been insufficiently heat-treated or only lightly salted. The infection causes digestive problems and severe vitamin B12 deficiency, or anemia.

Fish FAQ

How many times a week should you eat fish?

According to nutrition recommendations, 2-3 times a week. This provides enough omega-3 fatty acids and vitamin D without the risk of heavy metals building up.

Does fatty fish make you fat?

Even in fatty fish, the energy content stays well below that of fatty meat: Baltic herring provides 103 kcal/100g, pork 324 kcal/100g. On top of that, fish fat consists largely of heart-friendly omega-3 fatty acids.

Do fish oil capsules replace eating fish?

Not really. Capsules give you omega-3, but you miss out on the protein, minerals and vitamins of fish in their full range. Too much fish oil can also cause clotting disorders and an overdose of vitamins A and D.

Author: Marek Morozov

PS Come and train! ArtGym