How dangerous tuna?

Tuna belongs to the family scombers. Due to the sickle fin can reach speeds up to 80 km / h. Habitat - tropical and subtropical waters of the Atlantic, Pacific and Indian Oceans. An unusual feature is that the energy released in the movement, raises the body temperature of the fish a few degrees above the temperature of the water in which they live.
Tuna is by far one of the most frequently used in food fish. Tuna meat is rich in Omega-3 fatty acids and has the highest among fish protein content (about 23%).
But recent studies indicate that in any fish contains a lot of heavy metal salts, and tuna altogether holds the record for mercury content.

In this regard, nutritionists are increasingly wondering is it really the use of fish products 1-2 times a week brings only benefits to our health? Is it permissible to use such a large number of fish due to the high toxicity of maritime areas?
 
A large number of harmful chemicals enters the oceans as a result of human activity. The combustion of coal, the production of chlorine, cement, energy-saving lamps contributes to air pollution and subsequent settling of harmful impurities in water bodies.
Although the concentration of mercury in the fresh water is much higher than in salt consumption of marine fish such as tuna, mackerel, halibut is very dangerous for the health, compared with the use of fish from rivers and lakes. Why you ask?
  American scientists have proved that the most dangerous form of mercury - methylmercury interacting with the salts of sea water forms a very stable compounds.
  In contrast, in fresh water solar radiation contributes razschepleniyu methylmercury.
Algae, while at the beginning of the food web absorb methylmercury from the water, these algae feed on small fish. Species of fish that are long-lived and reach respectable size, are at the top of the food chain, and thus their meat contains more mercury accumulates in all organs and muscle tissue.
High levels of mercury in fish is particularly dangerous for pregnant women (mercury easily passes the placental barrier), nursing mothers and children. Cations are the most toxic methylmercury and and primarily affect the nervous system, and Precisely brain, liver, and kidneys.

Particularly high mercury content differs meat fatty fish - tuna, swordfish, halibut and shark meat. The larger and older individuals, the more mercury accumulates in its meat.
A very important point that you need to know especially fans of this fish is the fact that the tuna meat if not properly stored may form skombrotoksin (histamine, which is formed from histidine muscle tissue), cause severe poisoning (diarrhea, vomiting, swelling of the mucous membranes of the gastrointestinal tract), similar to the clinical picture of a severe allergic reaction.
Eating canned tuna, as opposed to previous recommendations (1 to 2 times a week) - a maximum of 1 time per month.