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Planning Retirement Online

Toxic fish

August 2012

ShellfishEveryone knows fish is good for you but most of us also know that eating “bad” fish can be a cause of stomach upsets and food poisoning. In fact the most common causes of food poisoning usually involve fish, especially shellfish.

There are two main types of food poisoning that occur from fish, ciguatera poisoning and scombroid poisoning.

Ciguatera poisoning usually comes from reef fish which covers most fish living in warm tropical waters, including barracudas, grouper and snapper, a fish often found in British shops.

The fish have had their flesh contaminated with toxins which cling to coral, algae and seaweed. When herbivorous fish eat these, the poisons transfer into their bodies. This is where the food chain comes in because in turn these smaller herbivorous fish are eaten by larger carnivorous fish to eventually reach humans.

You won’t know you are at risk of ciguatera poisoning, it is tasteless and odourless, and unfortunately is not destroyed by cooking.

The second main type of fish poisoning is scombroid. This is when a substance called histamine builds up in fish from inappropriate handling of fish during storage and processing, often when the fish gets too warm after it has been caught. Histamine is a chemical that acts as an alarm in an immune system and is found in commonly eaten fish such as mackerel, tuna, sardines and anchovies.

There has been concern about lead poisoning from fish which have lived in contaminated areas of the oceans and there can also be problems associated with fish which have taken in parasites and bacteria.

Symptoms vary but generally gastrointestinal upsets occur. Ciguatera poisoning usually develops with abdominal cramps, nausea, vomiting and diarrhoea. It can also lead to headaches and muscle aches. Scombroid poisoning will develop quickly and along with nausea and vomiting it can include hives, flushing and other symptoms associated with allergies.

In both cases, severe poisoning can bring on a number of serious problems which require medical attention.

Ciguatera poisoning can take a long time to go away - up to one or two weeks depending on how much of the poisoned fish you have eaten. Scombroid poisoning usually only lasts for around 24 hours. It is very rare though that either problem can be fatal.

Raw fish and cooked fish should not come into contact as they can cross-infect each other.

However, despite all this, generally the fish we eat especially here in the UK is very safe and very good for us. It is just important to ensure you buy from a good reliable source and keep the fish at the correct temperature in storage.

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