Healthy fish with toxins

Healthy fish with toxins

Healthy fish with heavy metals, worms and pollutants

Fish is healthy, that should have got around by now. It is easy to digest and contains valuable omega-3 fatty acids. But even with fish, consumers should be careful, because the one sold in Germany can contain pollutants such as dioxins, heavy metals and traces of antibiotic agents. Therefore pregnant and lactating women should avoid the consumption of tuna, salmon, herring, eel and swordfish as much as possible.

Fish is healthy, easily digestible and contains numerous valuable trace elements and cancer risk-reducing omega-3 fatty acids. However, toxic pollutants can accumulate in fish fats. In the past, especially in river fish, dioxin levels were measured that were sometimes extremely high. Harmful substances also accumulate in the fatty tissue in marine fish. But how dangerous could fish actually be for our health? Researchers and fish experts will be discussing these and other questions during a workshop at the Berlin-Brandenburg Academy of Sciences at the end of November. Some questions can be clarified in advance.

Improper storage allows bacteria to multiply
Can damage to health be excluded? To exclude them "of course they are never", as Horst Karl from the Hamburg Rubner Institute (MRI) told Die Welt. Karl is responsible for specialist questions in the field of fish parasites and residues at the institute. The institute is a nationwide facility for food research. The specialist sees the greatest problem with fish and seafood not in the environmental toxins, dioxins or germs that are actually present in all marine animals, but in the wrong storage. This would "most worry" the experts. Because like most fresh produce, fish should only be prepared very freshly or, if necessary, only stored for a short time and in sufficient cold. If the fish is exposed to high temperatures or is stored longer than usual, germs multiply rapidly. What most people don't know: "This also applies to smoked fish!" Sea animals that are bought at summer temperatures should therefore be stored in a cool place as quickly as possible. The longer the transport time, the more bacteria can multiply. This should definitely be planned in for shopping tours.

Toxins from microorganisms
In addition to diseases that occur due to long storage times, most people poison the fish ciguatoxin after fish dishes. According to experts, 10,000 to 50,000 people per year contract this worldwide. Those affected live almost exclusively in warm and southern regions, since the toxin is produced by microorganisms called Gambierdiscus. These tiny creatures can be found on corals. If sea creatures eat the microorganisms on the corals, the microorganisms are also absorbed. As a result, the poison accumulates in the fish body. For example, if a perch devours a mackerel, the poison is also deposited in the grouper. If the fish is later eaten by humans, the poison can also get into the organism of the consumer.

Food experts find it difficult to find contaminated fish. Because contaminated fish look no different and the smell does not indicate contamination. Cooking, freezing, smoking or marinating cannot defuse the poison either. Therefore, many people in Australia or Florida have completely removed fish like the barracudas from the menu. Ciguatoxin cases have so far only been found in Caribbean or Pacific regions. However, fish from these parts of the world are rarely exported to European countries. Therefore, people and holidaymakers, especially in these regions, are at risk from the toxin.

Small worms in fish
In addition to the poison, bacteria and parasites can also be detected in fish. Small worms such as nematodes, the herring worm or the cod worm live in the digestive organs of the fish. Those who eat infested fish may suffer from diarrhea, abdominal pain and nausea. The symptoms are similar to listeriosis. According to the expert Karl, fish suppliers, restaurants and traders are subject to legal provisions that are intended to reduce spread. This is how fishmongers have to screen the fish to discover the worms. If parasites do get on the market, only the tried and true recipe of heating or freezing helps. The worms are killed from a heat supply of 60 degrees Celsius or a cold of at least minus 18 degrees. To be on the safe side, the fish should be cooled down for up to 12 hours. When heating, care should be taken to ensure that the fish does not exceed 60 degrees on the inside, but on the inside. Then germs and parasites should be completely dead. When it comes to sushi, the fresh fish should be bought a week in advance and then "put in the freezer until shortly before eating," advises Karl.

Heavy metals and environmental toxins in edible fish
Heavy metals and environmental toxins cannot be removed by cooking. Shrimps are particularly badly affected. With increasing demand for seafood, prawns were primarily grown in aquaculture. However, infections spread extremely quickly in the small breeding tanks. The producers are therefore increasingly opting for antibiotics. Since 2000, substances such as chloramphenicol and nitrofurane have been repeatedly detected in shrimp. These have been shown to damage human genes and bone marrow. "The EU then set up a rapid warning system that can stop the flow of goods in just two hours," Horst Karl told "Welt". Fortunately, the warning system quickly eliminated the problem, so that the residues in the shrimp are rarely found. This problem was also encountered in salmon from breeding, but to a much lesser extent, since producing countries like Norway have always made aquaculture more advantageous. The cold water of the fjord alone reduces the risk of infection. In the case of wild salmon, organic salmon or freshly caught shrimps, there is no contamination of antibiotic medicines anyway.

Pollution contaminates entire fishing areas
However, wild salmon or freshly caught seafood may contain poisons such as dioxins and chlorine compounds. These arise, for example, from high heat in waste incineration plants, or from fires. The pollutants are absorbed by plankton in the sea and thus enter the animal's food chain. Dioxin accumulates in the fat and has a very high half-life. Due to the continuous intake, the toxic substances accumulate further and sometimes reach maximum values ​​for fish. Growing environmental awareness and a critical attitude on the part of consumers have been able to stop some serious sources of pollutants, so that dioxin levels in fish are slowly falling again, as Olaf Päpke from the Eurofins analytical laboratory in Hamburg reports. The company specializes in the laboratory detection of pollutants.

The maximum values ​​for dioxins and other harmful substances are set in the EU with guide values. These values ​​are criticized by the conservationists because they do not prevent excessive amounts from being deposited in the body if consumed excessively. The limit for dioxin is 8 picograms in one gram of muscle meat in the fish. According to the Hamburg laboratory, the fish from the North Atlantic currently reach an average of "0.3 to 0.4 picogram of dioxins". According to the expert, this is initially a reassuring result. However, the values ​​of fishing areas in which high concentrations were also detected earlier are In the past, large quantities of poisons were generated during industrial bleaching of paper, which was discharged into the rivers via the drains of many factories, which in turn flow into the eastern Baltic Sea, where high levels of dioxins can still be found today be measured.
Because the toxins have a long half-life and the water is hardly exchanged by currents, high values ​​can still be measured in fishermen in the eastern Baltic Sea region even though production has long since reoriented itself. According to the laboratory, there are on average three to five picograms in one gram of fish meat. Extremely high measured values ​​can be found in the vicinity of military airfields where chemicals were reloaded during the so-called "Agent Orange" during the Vietnam War. "There we measured up to 140 picograms of dioxins in fish muscle meat," said Päpke.

Fish rich in fat are particularly contaminated
The more fatty the fish is, the higher the levels of dioxins. This is because dioxins and other pollutants accumulate especially in fish fat. Accordingly, the dioxin concentration in fat herring is higher than, for example, in low-fat cod. The concentration of toxins in the European eel is often significantly exceeded because the eel has a fat content of over 30 percent. If, on the other hand, eel comes from a breeding farm, the dioxin content is significantly lower because the fish feed mostly has a very low dioxin content.

The expert, however, gives the all-clear all-clear for the heavy metals, which are also toxic. Since politics has ensured that emissions are reduced significantly, the levels of bleach and mercury in fish have also decreased. There are "hardly any problems here", says Päpke.

But what about radioactivity after the Japanese nuclear reactor accident in Fukushima? The radioactive are carried far out by the currents of the sea and greatly diluted. So there is no concern for the pollock that is caught off the Siberian coast. These fishing regions are far from the action and, according to the fish experts, would not be affected. The fish sticks that are particularly popular with children are made from Alaska pollack. (sb)

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Image: Günther Schad /

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Video: Keeping one step ahead of deadly marine toxins (October 2020).