Tuna is a low-calorie fish with high protein content and high nutritional value. However, in the meat of tuna there is methylmercury, which is toxic to humans, therefore pregnant and breastfeeding women should be especially careful about the excessive consumption of tuna.

Tuna is a large predatory fish that lives in sea areas mainly with warm waters. Various species of tuna live in the Atlantic, Indian and Pacific oceans and the adjacent seas, less frequently in cold waters, such as the North Sea and the Barents Sea. The largest specimens of the bluefin tuna species weigh up to 700-800 kg and live up to 50 years. On average, tuna weighs up to 200 kg, but there is also a species of "bonito", the weight of which does not exceed 20 kg. Tuna meat is characterized by a dark color - from pink to purple. It is the result of the strong blood supply to the muscles and the high content of oxygen-storing myoglobin in the tissues. This allows the tuna to move very quickly and maintain a high body temperature.

In recent years, the tuna catch has amounted to approx. 4 million tonnes per year. 68 percent of the fish come from the Pacific Ocean, 22 percent from the Indian Ocean, and the remaining 10 percent from the Atlantic and Mediterranean Oceans. The amount of fish that can be caught at any given time is regulated in order to prevent overfishing and thus endanger the extinction of the species. Particular attention is paid to overfishing of the largest species - bluefin tuna, which is a valued delicacy in Japan. Bluefin tuna is considered the most valuable on the market, reaching record prices at Tsukiji fish market auctions in Tokyo. In 2013, the tuna weighing 221 kg was auctioned for nearly 1.8 million dollars. In Poland, the consumption of tuna is small. Imports of this fish in 2014 amounted to 6.7 thousand. tone. This is much less than the imports of herring (54.7 thousand tonnes), salmon (101.7 thousand tonnes) or cod (35.8 thousand tonnes).

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Tuna: nutritional values ​​

Tunait is low in calories and at the same time is an excellent source of protein. 100 g of fresh fish provides 108 kcal, 23 g of protein and 0.9 g of fat, approximately 1/4 of which is the essential unsaturatedomega-3 fatty acidsEPA and DHA. These fats are very important in the diet, and their deficiencies favor, among others, low immunity, high cholesterol and heart disease. Tuna is a good source of Vitamin DVitamin D , which can contribute to bone he alth, immunity, and overall well-being. In Poland, in the period from autumn to spring, when the amount of sun is insufficient to produce the right amount of vitamin D in the skin, you should especially take care of its supply with diet and supplementation. Tuna is characterized by a very high content of B vitamins -thiamine(29 percent of the DV in 100 g),niacin(49 percent) and vitamin B6(45 percent). They are responsible, inter alia, for the control of energy processes and the functioning of the nervous system, which is why tuna is often recommended for physically active people. Minerals present in significant amounts in fresh tuna areselenium(52 percent DV per 100 g),magnesium ,phosphorusand potassium.

Content of selected nutrients in 100 g of tuna

Fresh tuna

Canned tuna made of water

Canned Tuna with Oil

Energy, kcal

108

116

198

Protein, g

23,4

25,5

29,1

Fat, g

0.9

0.8

8,2

Omega-3 fatty acids, mg

243

281

202

Vitamin D, IU

69

80

236

Thiamin, mg

0.4

0

0

Niacin, mg

9.8

13,3

12,4

Vitamin B6, mg

0.9

0.4

0,1

Vitamin B12, μg

0.5

3

2,2

Choline, mg

65

29,3

29,3

Calcium, mg

16

11

13

Iron, mg

0,7

1,5

1,4

Magnesium, mg

50

27

31

Phosphorus, mg

191

163

311

Potassium, mg

444

237

207

Sodium, mg

37

338

354

Selenium, μg

36,5

80,4

46
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Mercury content in tuna

Research shows that the vast majority of fish contain trace amounts of mercury and other heavy metals, which are toxic to humans, and the most of this element accumulates in the meat of butterfish, tuna, perch, eel and swordfish. Tuna is one of the fish with the highest mercury content because it is a predatory species that is almost at the end of the food chain, grows very large and lives for several dozen years. Mercury is stored in fish in the form of methylmercury, which is easily absorbed from the gastrointestinal tract, penetrates the blood-brain barrier and damages the nervous system. Methylmercury also crosses the blood-placenta barrier and into the milk of nursing mothers, which poses a high risk of fetal and infant malformations. Therefore, choose your fish carefully and only buy those from a reliable source.

A safe diet for tuna is two 100-gram servings per week.

Acceptable levels of mercury in fish are set at 0.5-1.0 mg / kg of fresh weight and pieces that are allowed for sale must these standardsmeet, therefore the consumption of fish should not pose a threat. The average contamination of tuna with methylmercury is 0.033 mg / kg fresh weight. However, be sure to eat fish with a high mercury content in moderate amounts - 1-2 times a week. As a precaution, pregnant, planning and breastfeeding women should not consume more than 100 g of tuna per week and it is not recommended to eat other fish at the same time.

Important

Note on the histamine in tuna

With all dark meat, especially canned fish, be careful with histamine. It is a hormone that occurs naturally in the human body, but in excess of sensitive people can cause severe allergic reactions. Its content is lowest in fresh fish and increases with storage time. Responsible for the characteristic smell of rotten fish. International standards set a maximum histamine content of 200 mg / kg of tuna meat, but people sensitive to histamine should avoid this fish.

Canned tuna or tuna steak?

Tuna is available from stores in large pieces in the form of steaks and in a can. The easiest to prepare is canned tuna, which is already cooked and you just need to add it to your salad, sandwich or main course. Proven tuna dishes in the lead role are spaghetti with broccoli and cherry tomatoes, tuna in a salad with grilled mango or tuna with arugula pesto with asparagus.

Canned tuna was first produced in Australia in 1903. The fish are usually gutted by hand, then pre-cooked whole for 45 minutes to 3 hours, cleaned, filleted and packed in appropriate portions into cans. Subsequently, sealed cans are heated under pressure at 121 ° C for 2 to 4 hours in order to eliminate pathogenic bacteria and ensure durability.

You can choose from tuna in water, oil and various sauces. You can find canned food with larger pieces of meat and very shredded. This is usually associated with the price, and the greater the grinding of the meat, the worse its quality. When buying canned fish, check that the can has no dents, signs of corrosion or is not bloated. After opening the can, the tuna should have a slight odor and a uniform pink color. The meat should be soft and not stretchy, but firm and in one piece.

This will be useful to you

Tuna steak recipe

A bit more difficult but also very quick to prepare a tuna steak, which is a noble element of the main course. A 2 cm thick steak should be spread on both sides with refined olive oil or anothergood fat for frying, sprinkle with s alt and pepper, leave for 20 minutes. To get a rare steak, fry it in a hot pan after 1 minute on both sides, medium rare - 2 minutes, and well-done - 3 minutes. You can season tuna in a variety of ways, such as with thyme and rosemary, or with soy sauce, lemon and sesame oil.

Sources:

1. Mania M. et al.,Fish and seafood as a source of human exposure to methylmercury,Rocz Zakl Panstw Hig, 2012, 63 (3), 257-264

2. http://www.portalspozywczy.pl/ryby/wiadomosci/spadl-import-pang-tunczykow-i-makreli,109566.html

3. https://en.wikipedia.org/wiki/Tuna

4. Self Nutrition Data, Fish, tuna, fresh, yellowfish, raw http://nutritiondata.self.com/facts/finfish-and-shellfish-products/4150/2

5. Self Nutrition Data, Fish, tuna, light, canned in water, drained solids http://nutritiondata.self.com/facts/finfish-and-shellfish-products/4146/2

6. Self Nutrition Data, Fish, tuna, light, canned in oil, drained solids http://nutritiondata.self.com/facts/finfish-and-shellfish-products/4145/2

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