Healthy fish with toxins

Healthy fish with heavy metals, worms and pollutants

11/21/2011

Fish is healthy, that should have got around in the meantime. It is easily digestible and contains valuable omega-3 fatty acids. But even with fish consumers should be careful, because the sold in this country may contain contaminants such as dioxins, heavy metals and traces of antibiotic agents. Therefore, pregnant women and nursing mothers should avoid as much as possible the consumption of tuna, salmon, herring, eel and swordfish.

Fish is healthy, easily digestible and contains numerous valuable trace elements and cancer risk-reducing omega-3 fatty acids. But in fish fats toxic contaminants can accumulate. Especially in river fish in the past, partly excessive dioxin values ​​were measured. Also in marine fish, harmful substances accumulate in the fatty tissue. But how dangerous could fish actually be for our health? Researchers and fish experts will discuss these and other issues at the end of November during a workshop of the Berlin-Brandenburg Academy of Sciences. Some questions can be clarified in advance.

Incorrect storage causes bacteria to multiply
Can health damage be ruled out? excluded „Of course these are never“, like Horst Karl of the Hamburger Rubner-Institut (MRI) opposite the „world“ said. Karl is responsible for fish parasites and residues at the Institute for Specialist Issues. The institute is a nationwide facility for food research. The biggest problem facing fish and seafood experts is not the environmental toxins, dioxins or germs that are actually present in all marine animals, but the wrong storage. This would be the experts at „most worried“ prepare. Because like most fresh produce fish should be prepared only very fresh or if necessary only short and sufficient cold storage. If the fish is exposed to high temperatures or stored longer than usual, germs multiplied rapidly. What most people do not know: "This also applies to smoked fish!" Sea animals that are bought in summer temperatures should therefore be stored as quickly as possible cool. The longer the transport time lasts, the more bacteria can multiply. This should definitely be scheduled for shopping trips.

Toxins from microorganisms
In addition to illnesses that occur due to long storage times, most people poison themselves after fish dishes on the toxin ciguatoxin. According to experts, 10,000 to 50,000 people worldwide contract this disease every year. Those affected live almost exclusively in warm and southern regions, as the toxin is produced by microorganisms called Gambierdiscus. These microorganisms can be found on corals. If sea creatures devour 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 also deposits in the grouper. If the fish is later consumed by humans, the poison can also get into the body of the consumer.

It is difficult for food experts to find contaminated fish. Because contaminated fish do not look different and also the smell does not indicate a contamination. Also, cooking, freezing, smoking or marinating can not defuse the poison. Therefore, many people in Australia or Florida have completely eliminated fish like the barracuda from the menu. Ciguatoxin cases have so far only been found in Caribbean or Pacific regions. From these parts of the world, however, fish are rarely exported to European countries. Therefore, people and holidaymakers, especially in these regions are endangered by the toxin.

Small worms in fish
In addition to the poison, bacteria and parasites can 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 dealers are subject to legal provisions intended to reduce their spread. Fishmongers have to study the fish to discover the worms. If parasites are still on the market, only the well-tried recipe of heating or freezing helps. The worms are killed by a heat 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, it should be ensured that the fish does not exceed the outside, but from the inside 60 degrees. Then germs and parasites should be completely dead. For sushi, the fresh fish should be bought a week in advance, then this one „until just before the food in the freezer place, "advises Karl.

Heavy metals and environmental toxins in food fish
Heavy metals and environmental toxins can not be eliminated by cooking. Shrimp are particularly affected. As seafood demand increased, the shrimp were bred ostensibly in aquaculture. In the small breeding tanks, however, infections spread rapidly. The producers therefore rely more on antibiotics. Since 2000, shrimp has repeatedly been found to contain substances such as chloramphenicol and nitrofurans. These have been proven to damage the genome and bone marrow of humans. "Then the EU set up a rapid alert system that can stop the flow of goods in just two hours," said Horst Karl „world“. Fortunately, the warning system quickly eliminated the problem so that shrimp residues are rarely found. Although this problem was also found in salmon from breeding, production was much lower, as producing countries such as Norway have always been more interested in aquaculture. Alone the cold water of the fjord reduces the risk of infection. In the case of wild salmon, organic salmon or freshly caught shrimps, the contamination of antibiotics does not exist anyway.

Pollution contaminated whole fishing areas
However, wild salmon or freshly caught seafood may contain toxins such as dioxins and chlorine compounds. These arise, for example, at high heat in waste incineration plants, or by fires. In the sea, the pollutants are taken up by plankton and get into the food chain of the animals. Dioxin accumulates in fat and has a very high half-life. Due to the continuous intake, the toxic substances accumulate more and more and in some cases reach maximum values ​​in fish. Due to growing environmental awareness and a critical attitude of the consumers, it was sometimes possible to stop serious pollutant sources, so that dioxin levels in fish slowly sink again, as Olaf Päpke from the Eurofins analytical laboratory in Hamburg reports. The company specializes in the laboratory detection of pollutants.

The maximum levels of dioxins and other harmful substances are set by reference values ​​in the EU. These values ​​are criticized by the conservationists, because they do not prevent excessive levels of consumption from being deposited in the body. The limit for dioxin is 8 picograms in one gram of muscle meat of the fish. The fish from the North Atlantic reach according to the Hamburg laboratory currently on average about „0.3 to 0.4 picograms of dioxins. "In the opinion of the expert, the results are reassuring, but the values ​​of catchment areas that used to show high concentrations are still high today, as was the case with industrial bleaching of paper In the past, large amounts of poisons were sent to the rivers via many factories, and the rivers once again flow into the eastern Baltic, where high levels of dioxins can still be measured.
Because the toxins have a long half-life and the water is hardly exchanged by currents, it is still possible to measure high levels in fishermen in the eastern Baltic region, even though production has long been reoriented. According to the laboratory, there are on average three to five picograms in one gram of fish meat. Extremely high readings can be found in the vicinity of military airfields on which during the Vietnam War chemicals under the so-called „Agent Orange“ have been reloaded. "There we measured up to 140 picograms of dioxins in fish muscle meat," explained Päpke.

High-fat fish particularly stressed
The more fatty the fish, the higher the dioxin levels. This is because dioxins and other pollutants mainly accumulate in fish fat. Accordingly, the dioxin concentration in fat herring is higher than, for example, in low-fat cod. The toxin concentration in European eel is often significantly exceeded, because the eel has a fat content of more than 30 percent. In contrast, if eel comes from a breeding, the dioxin content is significantly lower, because the fish food usually has a very low dioxin content.

A first but cautious all-clear gives the expert Päpke in the also poisonous heavy metals. Since politics has ensured that emissions are significantly reduced, the levels of bleach and mercury in fish are also falling. Give it here „hardly any problems“ 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. For the saithe, which is caught off the Siberian coast, there is therefore no concern. These fishing areas are far away from the action and, according to the fish experts, would not be affected. Alaskan salmon are used to make the fish sticks that are especially popular with children. (Sb)

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Picture: Günther Schad